Exotic O - Green Rocks with Chris Mattinson

buffer boy one of many today it's a beautiful afternoon here hello everybody welcome to the backyard the local time is 1 44 on a friday afternoon and we will begin our program called green rocks with chris mattenson at the top of the hour at two o'clock local time but between now and the top of the hour we're going to test things out make sure we're functional and we're going to do a few thank yous and things of that nature here we are today talking about green rocks session o of the alphabet and you are welcome you are invited to come back for session p sunday morning 9 a.m pacific time that's our usual time to go to the eastern cascade foothills not the western so the last time we were on the western foothills of the cascades we're going to go up and over the crest and look for some siblings rockwise and the eastern foothills of the cascades okay well that's enough speaking to just see how we're doing here and the sun is brilliant at the moment and looks like it would be brilliant for the rest of the afternoon how are we doing here where's my little mug here how are we doing five by five that's wonderful mug by pat yeager i recall is that correct pat from tacoma thank you our guest has the other mug as well uh ashley hello tennessee uh i love green rock says myra garrett the dutch night owl is with us to jurassic coast in the united kingdom minnesota so far so good says somebody so they know the experience i've had in the backyard here loud and clear says scott from phoenix arizona michael's in ireland hello good evening elsie in the uk are who's denmark ben is saying hi to kathy oh there's kathy she's from brisbane australia live must be early for you kathy geologically speaking in the hizzy that's todd smith ladies and gentlemen from southern california hello patrick northampton uk frederick jennifer's skipping work in boise hello from germany las vegas blodgett oregon we have many familiar names here ben is in the netherlands south wales edmonton alberta tokyo hello denise so i trust we're doing okay huh we're doing just fine um chris would you mind uh turning your mic on and we'll we've got a two mic setup baby this is this is advanced okay so chris has got his mic turned on can i ask about uh chris so chris can you tell us a little muffler boy there's gonna be a lot of that i'll try to ignore it i promise i know it's obnoxious chris where did you grow up and where did you go to school so i grew up in california in central california if you believe that concept or southern california if you're more of a dividing the state in two pieces and i did my undergrad degree at uc santa barbara uc santa barbara i went to stanford for my grad work and in 2008 came up here and joined the faculty nice 2008. it's been that long it has scary wow more than 10 years okay how did that go with chris 5x5 for chris says daniel a couple more reports on chris they can hear you fine oh that's really nice to hear so we're going to be switching spots here you know we're going to keep our distance of course uh we've got a slight breeze um oh good good good so it's working i think just keep it on if you don't mind okay yeah you know and nick for your info um yeah muffler boy isn't nearly as loud on the on the receiving end as he is here in the yard so all right now chris has been a loyal watcher and just like you guys and you guys are all saying you know you can't hear muffler boy but i don't know i just it makes me feel better to i need to stop that's the point i'm the only guy that can hear it so i just need to stop come on nick it's part of the stick [Laughter] what is this live live stream number 90 or something you can't stop now it is it is something like that okay it's time for some thank yous so a little housekeeping from the last show i shared uh there was the name of a cat in portland that sent gifts to bijou who's inside the house napping by the way and you remember this there were these cute little cat toys with very potent uh this is washington this is oregon this is a key lime pie and everybody was asking i watched the replay everybody says well if it's so potent like where can i get it so uh cat so this this very effective i can endorse the effectiveness if you're looking to drug up your cat uh cat nip this episode of nick from home brought to you by catnip toys uh catniptakeout.com and a little punch card if you really want all right so i wanted to follow through on that and i felt bad because you remember last friday i had the halloween gifts and it was uh jay and eric from sacramento that sent this enormous box with these three big things and i was assembling the halloween gift and it ended up being do you remember this frankenstein frankfurters with bloody ketchup inside of a stein of beer and i didn't even think to take the paper thing off of the stein well i'm sure you guys were disappointed when i didn't actually reveal what was on the mug which you made custom for this show so here it is steve and jay sorry here it is eric and jay a toast to mew to meow so i feel better uh doubling back on that so thanks fellas there's a personalized monk for you here yes there you go they could hear that click chris now i had to make sure to grab a gift from my office uh one of the all-time gifts from last spring because it fits in perfectly with this show so do you remember this gift this is all handcrafted and this rock was collected personally by steve it's the same steve as cozy fort by steve but it's a green rock damn it and i emailed steve this weekend this week and i said hey remind me where you got your green rock he said burlington hill and that was the easton metamorphic suite we were talking about last time and we will talk about the easton metamorphic suite again today so thanks again for this gift from steve it's it's proudly on display in my office but i brought it home for this special occasion steve it's going back to the office tonight and speaking of custom stuff this just arrived an hour ago from dogny in spokane i couldn't resist sending you a personalized coffee mug be sure to read the fine print i looked for exotic terrain coffee but i couldn't find any go figure maybe just maybe there's some exotic terrain around mount spokane in in in the spokane area my brother clint got me watching on your youtube shows and we both enjoy it i'm now obsessed here's to you okay so thank you dognie so dognie sent some coffee from there is a a peak called mount spokane north of spokane it's not really an exotic terrain story but if we ever do a chalice series of live streams that's part of that show but how about the personalized mug after i wipe my nose here excuse me this is only going to make sense for those who have been with us quite a while mello grello do you remember what grello the color grello stands for on her exotic terrain map a combination of gray and yellow grello i think it's a color i made up maybe not a product of cash creek hello grello oh nice job dog knee thank you and speaking of colors as soon as i said in the last show as soon as the words left my mouth my coloring pencils are down to their nubs i knew i shouldn't have said it i still have plenty of lead left in those colored pencils but patrick and his mother to the rescue patrick i've been having a blast with my 72 new colored pencils half of which i've already earmarked for specific terrains that we will be discussing in the next month patrick but all these crazy different shades of green and yellow and brown and blue i'm using all of them i'm using a lot of them and patrick and his mother teresa wind's picking up they sent me some white paper that's like legal pad length so that i don't run out what does patrick's note say hi professor nick i picked these out super special for you i hope you enjoy the colored pencils on the paper maybe it will help you have enough room for the alexander terrain and others love patrick thank you patrick thank you teresa and one more and we can finally get to our guest and we can get to the top of the program i still got four minutes according to my watch julie from prosser drove up from prosser last sunday i missed her we were done live streaming and i was out on a hike immediately to clear my head but when i got home this was waiting for us dear nick a travesty i cannot bear to see you drinking cupcake cellar's wine of all things please man friends don't let friends drink exotic terrain wines here is some washington wine from the german chocolate cake this is the good stuff please share with liz but don't let her drink all of it julie from horse heaven hills st michelle wine estates washington's best ava so isn't that nice julie must have delivered a bottle of wine well she delivered a case of wine and we haven't been the same since so we have been enjoying the wine tremendously liz and i at the end of a day on talking about today's event so thank you julie and chris uh our guest and i will enjoy a little bit of the wine at the end of today's show so thank you for your generosity julie from prosser okay that's plenty checking one more time to see if we're in good shape uh i don't have to uh collect my head too much because i'm only talking for the first 10 minutes and then i'm going to be kind of having chris do much of the hefty lifting to heavy lifting today but i'll be of course part of the proceedings a little show and tell everything else oh everything's looking good that's great you want to try one more time uh so you went to stanford in what years were you at stanford uh well i started in 2000 and then i worked there in the iron probe lab and did some teaching for about three years before coming up here so okay 2000 to 2008. yeah more than more than half a decade for sure so chris is a soft-spoken guy but that was working okay for you i don't think it'll be any different when he's standing here it's not going to make a difference is good okay i finally figured out the microphones i finally figured out how to both work you know i've heard you say well i'm only going to talk a few minutes here so that's why i say that ambrose fierce you know i will go straight at my story without introductory remark as is my custom getting the business from the guest i love it nice all right give me one minute and we will start and i promise my introduction will be short that sun is especially strong so i don't i don't know we'll we'll work with it it looks good on screen but you got it got to squint i think a little bit more than a little bit all right thanks again for doing this sure thanks for having me oh you bet steve i'm going to put your gift off to the side i don't want to trip over it or have anything happen to it so i'm sure i'm showing it off one more time steve sir pentonite from burlington hill between everett washington and bellingham washington uh well a pleasant good afternoon to you all thank you for tuning in for this episode of our exotic terrain live stream sessions that's wordy uh a to z uh today is a is a unique episode and we're taking a break from our march through all of these exotic terrains we were up in british columbia for a while and we're finally now down in washington but there are so many of these green rocks that are in some of these exotic terrains that we needed an expert in my opinion because i don't have the expertise to really understand how to read some of these green rocks so we'll do some live q a we might do more than the normal amount of live q a because you have a rare opportunity to talk to somebody who knows more than most about igneous and metamorphic petrology and he also has a lot of experience here chris matinson who i work with he's the department chair here at the department and so he's a very busy guy and yet he's carved out an hour to be with us this afternoon we have two objectives and really two objectives only this afternoon anything beyond that is just kind of extra bonus coverage so goal number one is to get some help from chris as to what's going on with all these rocks these are all names and the names have vague connotations for me and to be honest i've been doing enough kind of programming to the general public where i just say yeah this is a green rock and it's from the oceans well that's not good enough that's not good enough so how many of these words pertain to rocks versus something else number one of the green rock names which are from the middle of the ocean which are from the edge of the ocean in other words what's a specific story that some of these green rocks can tell us that's objective one the other objective is how do we identify a couple of these things like i had chris over last night just before it got dark and he said i want to see some of the green rocks you you have in your backyard so i know what i'm working with and he brought a few of his own uh to supplement my little collection um but you know i don't know what i'm looking at i know it's a green rock i don't know is this ophiolite is this serpentonite is this jade is this dunnite i don't know the difference i don't know how to tell them apart so you hear my two messages how can we tell these rocks apart just identification wise and then also what stories can they tell uh from our geologic past as it pertains to our exotic terrain story the last two minutes of my introduction i promised buddy i promised that i want to remind you where we started getting into green rocks larry ladder's a little wobbly suddenly i don't understand why so i'm not going to get the clipboard for this but we looked very this is last time now this is on sunday morning and this is from ned brown's work and we're up uh surrounding mount baker so mount baker is in the red triangle and here's the town of bellingham where two of our boys went to school and so this is an amazing area between bellingham and surrounding mount baker and i don't need to go through it all but i do still want to show you that that green stuff is the easton metamorphic suite and there's a variety of kind of truly green rocks that's why i picked green for the color in this eastern metamorphic suite and if you come back on sunday morning we're going to see more of this eastern metamorphic suite not by bellingham but close to ellensburg believe it or not just right over there and pointing to the west so that's the application of much of this green material we're going to be continuing to use exotic terrain material that's green hey that's it i'm done with my intro i hope that you feel comfortable with what our objectives are are you still there i don't see any comments streaming at the moment let me just pause and make sure you're still connected with us oh god they're already asking questions about jadeite and nephrite and everything else so chris would you mind i'll keep i'll keep my distance from you and uh please feel free to start however you want just kind of introducing yourself or getting into the content right off the bat um sure well thanks nick thanks for having me over um so yeah i guess we'll just launch in so thinking about nick's uh theme i thought i might start off by uh paraphrasing slash plagiarizing a well-known quote and thinking about how we can think about these different rocks and uh some rocks are born green some rocks achieve greenness and some rocks have greenness thrust upon them uh so i thought that might be kind of a fun way to frame slightly what we're going to be talking about here that shadow out of your face good good i like that sure so uh nick did you just want to start with just kind of going through some of that terminology or well i'll tell you what let me get you rolling this way so i can i can keep my distance here okay so um on the chalkboard chris i've got these these two different settings that's where i'd like to start if you don't mind so how many of these rocks pertain to a subduction zone versus something that's not a subduction zone okay so yeah great um layout here um so pretty much green rocks most of those on there are either associated with mafic rock so basalt composition rocks or ultramafic rocks so mantle composition rocks and you get both of them in these two settings but you get different types of them so we can think about it in terms of composition mafic versus ultramafic and we can also think about it in terms of pressure and temperature so as a petrol just that's how i think about it so in your your show you've been doing a lot with things moving laterally either coming in and accreting strike slipping along the margin but we also think third dimension where are we in depth where these things are forming okay and so if you think about uh mid-ocean ridge you have the ocean plates pulling apart you have hot wet hot mantle welling up to the surface you have high temperature relatively low pressure conditions you've got a lot of hydrothermal circulation that's where a lot of those green rocks are coming from in that setting okay uh whereas in the subduction zone you have the plate diving back into the mantle high pressure low temperature conditions so different physical conditions leading to different rocks okay uh so that would be kind of the overview picture i like it is there a hand sample anywhere within reach i can grab your mug from you give you some hands sure do you want to just try to show and tell a little bit sure like is there a any of those that are for sure a subduction zone rock versus uh ophelia or a spreading ridge rock absolutely let's see you had uh a sample of the uh grinch's blue chest from french well let's take a big one here big one uh is that is that a decent one or do you want to do even bigger um ah that's a good one yeah i'll switch out okay so uh yeah well let's see nick is the expert on this but uh just sort of holding this the sample up hopefully you can see there's a bit of a bluish tinge to it a little bit of uh greenish so this is uh let me switch you yeah all right we'll keep our distance i'm gonna flip you around and see if this works okay we're looking at a blue shist metamorphic rock at the moment that's a big sucker nope all right i'm coming back the light's wrong for that so uh you go ahead and keep talking if you like chris what can we point out here so this particular sample really fine grain so you're going to be a little hard-pressed to see a whole lot on the camera you can kind of see a sheen to it but the the blue and the green there those are some some minerals we can get into that a little more later but but that type of rock is really the the smoking gun of a subduction zone setting subduction zone so we're for sure where are we in the subduction zone with the blue shist um blue chest a pretty low temperature um high air pressure but not the highest pressure okay so um you know in terms of of depth you're probably down um 30 40 kilometer burial depth very low temperature we're down at you know maybe 300 degrees centigrade type temperatures okay uh and just for comparison if you just think about where you are in some random place at uh 40 kilometers depth okay um oh sorry you're good you're probably uh you know you're probably looking at um you know let's say if you're in the mid continent you're probably looking at you know 500 600 degrees c if you're in a you know where we are in a more uh tectonically active area a bit more than that um okay and if you're the mid-ocean ridge of course you got really hot stuff you know you got magma just a kilometer below the surface right at the ridge okay well this we have a fair amount of blue shift and we're going to look at some beautiful blue shifts uh on sunday uh and you're saying first takeaway is we we we can't make blue shifts to any other place it's got to be a subduction zone right because pretty much where do you get those those those low temperatures at such great depths give us the temperature range again in the pressure range again off the top of your head for a blue shift oh gosh blue schist um you know that particular one that's probably uh around seven kilobars so one one bar is ballpark atmospheric pressure so about seven thousand times atmospheric pressure wow and a handy rule of thumb is uh one kilobar of pressure that represents a burial depth of between three and three and a half kilometers in the earth if you just think of the weight of the overlying rock column okay um so we're down probably uh seven uh or so kilobars for that stuff um let me show another one that's even bigger but i'm feeling like i need to show off oh baby blue schist from a place called french cabin mountain we'll talk about it now can you give me i need to give myself a break uh is there a zone or a particular finger point on that subduction zone where the blue shift where those temperature and pressure conditions are uh sure you'd be right in uh kind of this zone i mean depending on if you're drawing the crust versus the whole lithosphere here uh you know if this is the surface and um you know you got to get down to it to enough depth to to form those high pressure minerals but if you go too far you're going to transition that into an eclogite pressure and higher temperature hold off well okay let's let's do it that was that was i don't think we have an eclipse do we oh he brought a necklace of course uh all right this is go for it okay this is not a uh let's see where's the which end is the camera on oh it's just kind of the camera the lens is probably just up uh okay let's oh i'll give you uh it is tricky yeah maybe you're better at this one all right so this is an eclegite so this is not a local rock this one's from norway actually but it's a beautiful eclide uh so the green mineral is a is a green sodium containing pyroxene and then there's beautiful red garnets in there uh so that's what that rock nick was just showing there he'll turn into well that was my cue subducted enough so you take this which is a metamorphic rock a metamorphic blue shist because it has kind of a blue sheen to it what are the minerals in a blue shift so the blue mineral is a blue amphibole okay it's called glocophane and it's a sodium rich blue amphibole really the most distinctive thing and then that's got the green in there um epidote is one of the main minerals there so that's a pretty common mineral you see a lot it's got that really distinctive pistachio green or avocado green color to it um and forms in a wide variety of of environments okay um so so you had us it's kind of semi-shallow for the blue shift and you said if we go deeper in the subduction zone yes we're getting this now what minerals are here then so the green mineral is that green sodium-rich pyroxene sorry um and the red is garnet so that what's interesting about that is the density it's about 3.5 grams per cubic centimeter which is actually higher density than the mantle that's down at those depths so that's part of what gives that pull force to a subduction zone part of what's driving the plates yeah is those metamorphic reactions increasing the density as part of that subduction process okay other thing to note garnet and pyroxene neither of those minerals have water in them okay the blue chest you've got the glocophane it's an amphibole amphiboles contain water and the epidote also contains water okay so you're going to higher density but less water trapped in the mineral structure and it's that release of water which of course is feeding the volcanoes like mount saint helens also uh is playing a role in some of the earthquake activity in the plate as well okay all right let's take a break for a second i told you this guy was encyclopedic i mean it's amazing uh you're hearing him okay number one i have an improv i think i want to do with larry the latter here and we'll see if we can get some close-ups with better light but let me pause are we doing okay with just the the audio and the visual just in general i know chris isn't perfectly framed up et cetera but i'm just kind of okay the audio's good on you chris okay i'm gonna try this you know that's the beauty of this live streaming you're not plugged in so you can just kind of what if i do this come on larry get settled thank you talking to the ladder now okay okay all right i'm talking to you now viewers isn't this better can't we see better now with the zoomed up camera crappy grammar there but they love the audio i'm still waiting okay they like it um so chris let's see do you want to feed me while we got this good setup do you want to feed me a few others and just you can kind of just talk to us about what we've got sure so here's one maybe we should even started with this one this is uh the basalt before it's been cooked up too much so this is what my colleagues my old advisor would refer to as a popcorn pillow so that's actually a little piece of a little tiny baby pillow basalt there you can see that rounded shape to it so that's basalt but it's just started to turn a little green it's just been cooked up yeah very little bit so this is kind of what what you get when the thing's just barely heading down the trench so it's still a basalt but it's kind of like a slightly metamorphosed basalt very slightly metamorphosed yeah all right and by the way is that now let me no no i'm getting greedy now i want to get the hat i want to get you on camera too all right so we'll try this and oh [ __ ] sorry patrick all right um yeah um so so far we've talked about green schist is green just originally sorry we've talked about blue shish does the blue just originally basalt like can we take all this stuff back the composition of that little popcorn pillow and the composition of that blue shift that you were holding in the composition of that eclegit are all just about the same they're all a basaltic composition huh okay so the reason they're different is because of different pressures and temperatures leading to different minerals got it thank you all right so we start with a basalt that is slightly pillowed like this if we keep going way down the trench and we're past the blue shift zone we're now to this eclegitite thing and the garnets are popping up because of the uh high pressure high pressure so the garnet is a high density mineral the pyroxene also high density mineral eclegite okay uh what else anything else is green shift part of this green shift is is um part of this it depends on your temperature so if you're a little higher temperature you're going to go through the green schist faces and kind of depending on exactly the relationship between pressure and temperature yeah controls which faces you go through if you're imagining a subduction path so if you have a subduction zone like ours here the cascadia subjection zone right off the coast it's pretty young oceanic crust the spreading ridge that's generating that is not too far offshore and that subduction rate is pretty slow so in other words there's plenty of time for the heat to conduct in so really the name of the game is the is the contrast between heat conduction which is slow and the pressure increase which of course is instantaneous as as you're increasing in pressure pressure goes up right away got it but it takes a while for the heat to conduct in so we're we have a relatively warm subduction zone here so based on the thermal modeling we're expecting that is going to pass through the green shifts faces and have uh not much bluishest faces at all here whereas if you go the other end of the extreme in northeast japan you have a very old pacific plate yeah old and therefore cold and therefore more dense and sinking more rapidly into the mantle um the heat isn't conducting any faster but it's going down a lot faster so you follow a much colder trajectory uh in that case and yet we have a ton of green just like the shucks and green schist and that sort of thing right yeah uh and what's interesting i won't make you lift up that big block and i'll do it challenge okay okay go ahead all right so there if you um i don't know about seeing it in that piece but at that locality you can see it's actually inner layered blue shifts and green shifts oh yeah um and so so our big picture is pressure and temperature is what's controlling that and we're saying well this is all pretty much a basalt but the layering comes in because well pretty much isn't exactly the same so there's small differences in composition controlling whether you're getting that blue amphibole or you're getting those those green minerals so okay the green schist you've got the epidote which is green uh chlorite another green mineral that's that platy uh mineral but since it's usually pretty fine grain you don't you don't see the individual grain so well i gotcha um actinolite a green amphibole um and then there's some albite in there the um phelps bar uh whereas in the blue chest you've got the blue amphibole that glocophane and then you can you can have that epidote commonly present there are other minerals that could be present as well okay but once you get that blue amphibole you start really noticing the blue color to the rock which is really nice in those particular samples okay so we're scoring at home and we're subduction all the way so far yes anything else that's an obvious subduction zone related uh rock that you can see here um you know i i do have some others maybe we'll wait on those until later okay and uh well what the heck we can show one that boy so this is actually totally different geological environment from what i was just talking about but it's rare that you actually see beautiful epidote uh and here's a piece where you can actually see some beautiful individual crystals so this is actually from the denny creek scar and just on the other side of snoqualmie pass so pretty local so this is where the magma from a pluton as part of the cascades arc invaded some carbonate rocks and marbles and limestones and and so forth and as part of that reaction form this beautiful really coarse grained epidote usually it's just fine grained pistachio green uh and that's all you see but so this is a mineral not a metamorphic rock yeah i mean that well that rock overall it's kind of on the okay it's uh yeah depending on your perspective metamorphic it's got igneous processes metamorphic processes involved um kind of on the boundary there i got it um but totally different pt environment but just so you can see a unusually beautiful sample of epidote and i'm sorry i'm distracted here so you might have to repeat so the epidote uh is a metamorphic mineral it only thrives in this kind of high temperature pressure situation or not uh well evident actually has a pretty broad stability range okay so of course it's classic for the green shift species but it can also occur in blue shifts you can also get it in epidote sorry eccledride faces and then you can actually get magmatic epidotes so epidote in unusual circumstances can form from a silicate melt in a magma and we actually have some examples of those in the cascade you only get that when it's crystallizing pretty high pressure i see because the epidote is a high density mineral i see okay that's a beauty thanks for bringing in just some quartz nearby yeah there's some quartz there's quite a number of other minerals from that locality uh some of them common minerals some of them rather unusual but that i brought that just because so you could actually see one of these minerals that we're talking good good how about more i think this is working people are digging this stuff i don't know if this is anything in the same ballpark or you want to take a big detour here well i was thinking we might take a detour away from the mafic rocks okay and look now to the ultramafic ultra mafic what is that so i don't think we're going to take the time to actually mark things off necessarily but we're we're trying to hit some of these words here and we just dealt with blue shift and a little bit of green shifts and we're just looking at an eclegite and and chris has been talking about the fact we've been dealing with mafic uh rocks basically kind of basaltic uh compositions and now we're switching this is rubbed off already ultra mafic totally different world and i'm all ears about this this is the good stuff sure so again mafic it's referring to that high that magnesium and iron that's where the mafic term comes from mafic think basalt there's a variety of terms out there but think basalt composition okay so it's a composition of a basalt but as we've seen those rocks you were just showing those are no way or that would you call those of assault well except for the little popcorn pillow right you could call that one right it's the same composition okay so ultramafic yep more magnesium and iron lower in silica um so when we think ultramafic primarily we're thinking mantle rocks you can get some other environments in the crust where you can form ultramafic compositions but the mantle is you know our biggest example of ultramafic composition so and very rare to get ultra mafic at the surface to get mental rocks at the surface is not a common thing right because they're they're dense yes uh so typical mantle rock about 3.3 grams per cubic centimeter for density or 3.3 times more dense than water might be a uh an everyday way of thinking about it whereas something like most uh continental rocks so mount stewart you're probably dealing with 2.8 grams per cubic centimeter something like that okay 2.7 2.8 2.9 in that range so normally the dense stuff wants to stay down deep and the sh and the less dense stuff is floating on top of it so you need some geological process bringing these things up to the surface good um and you know there's a few different ones so maybe to start out with um here's uh a sample so this is from the twin sisters doneite we're talking about before haven't you been to the twin sisters done i no but you have uh not i've been close to it um so that was a sample we actually got donated to the department by the uh the mine operator there so they're actually quarrying this stuff okay um it's amazing beautiful fresh olivine so dynite is a rock that is 90 plus percent olivine uh and that's a beautiful fresh example of it this is amazing um and it's unusual to have something that fresh make it up to the surface so that's a really beautiful example there almost all of that olivine and so that's an example of an ultra mafic rock and we know it's mantle because of the olivine or there's other reasons we're just looking at this in hand sample we know it's from the mantle well uh good point i haven't actually studied this particularly but typically if you want to figure out mantle versus crest composition so the comp we can look not only at the bulk composition of the rock but also the composition of the individual minerals okay so an olivine coming out of the mantle that's about 90 percent magnesium n member so olivine has a compositional range from magnesium rich to iron rich out of the mantle very magnesium rich about 90 percent or so wow whereas the other place where you can form olivine is you know you can crystallize that out of a basalt yeah hawaii um and you can get accumulations of olivine so how do we know that isn't just some pile of olivine you know in some shallow magma chamber right but typically that's a much more iron rich composition of olivine you get in that setting so i haven't analyzed or measured uh from the twin sisters so that would be a way to tell the difference twin sisters dunnite an example of an ultramafic rock from the mantle the other thing we can also look at the other minerals that are in there i don't know if you can see it at all in that piece you might see some little black shiny minerals in there i think right there yeah uh so that's the mineral chromite so it's an iron and chromium oxide mineral so where that actually accumulates in masses is a it's a major ore of chromium um so the mantle rocks high in chromium um and nickel as well compared to stuff you get in the crust okay so that's another thing we can look at that's a beauty okay we got a good look at dunnite i'm very happy i've never been to the twin sisters done it but i'm pretty close because of your ex your hand sample so is dynamite specific type is a specific rock name okay for an ultramafic rock that has more than 90 percent olivine in it okay so we can think about ultramafic as the broad compositional category donated is a very specific rock name within that another rock term that you'll run into is peridotite good donite is within that bucket that you would count as peridotite so peridotite extends down to more orthopyroxene incline of pyroxene so for our mantle rocks um we're dealing primarily with uh did you have some there's pretty tight there you're not oh we can we could save that one for a moment but uh yeah so um often you know these these um terms will get used semi-interchangeably ultramafic peridotite uh and so forth so peridotite you're just something that's somewhere that's a primarily a mix of olive incline of pyroxene orthopyrrexin okay and uh fairly broad i think it's you know if you're at least 40 olivine or something i forget what the cutoff is there um and so uh maybe we could look at this sample let's do it next here is this a prototype this is a peridotite you guys ready for a prototype i'm getting a lot of comments here about this is amazing this is great whatever so keep it going chris we just lost our son but we'll be all right yeah so this one i think is interesting this is um a prototype but it's got more in it than just alvin um and you'll see it looks a bit different so first a comment even though this is not a dynaite it does help illustrate where donite gets its name so all that kind of yellowy tan color on there that's what olivine looks like after it's undergone a little bit of weathering so it's a done color uh so i don't know if we use dunn as a color for anything other than horses uh and ultramafic rocks but doneite but what you can see is there's clearly other minerals in there yeah and so this is a particularly special sample this is also from norway this is a garnet peridotite now normally we don't associate garnet with ultramafic rocks we think oh you know you can have garnet in a shift you can have garnet in a you know maybe an amphibolite or something but you don't normally think about that it's because you have to be deeper than ballpark 100 kilometer depth to stabilize garnet okay so bingo immediately know you this thing is way deep if you see that garnet in there the other mineral you can see there's some little tiny bright green kleinopyric scenes in there um you guys see them i don't know if i do you know if we get the sun back they'll probably show up okay a little better uh they're much smaller than the garnets okay um but again i was saying that that there's a higher chromium content in these mantel rocks and so when you have the klein of pyroxenes that chromium goes into the clinopyroxene and just a little smidge of chromium will give it this beautiful bright green color and if the sun comes back we could maybe get a better look at that good um so that rock mostly olivine but it's got some cleaner pyrixine also got the garnet in there so garnet peridotite so that's you know deep really deep metal the dynite probably something uh shallower can i throw you a curveball is this the look of olivine or the same kind of kind of a weathered olivine look or not necessarily so um so i think this is a nice segue so you go from something like that to something like this um basically just add water at low temperature so serpentine oh okay that's a serpentine well jeez it i believe you you're the expert i don't know if i believe me um you did say it was a curveball i did i did you've definitely got a more convincing serpentine okay over here yeah but um so remember this stuff is down in the mantle high pressure high temperature that much water around uh you bring that stuff up to the surface below about 500 degrees centigrade you add water that olivine is going to convert over into serpentine okay um and so we get the most exciting sure yeah that's a beautiful sample there now you guys first of all if you're confused why are we using this weird camera lens with the rope in front and everything it's the high mag high magnification uh thing out the back of the phone so that's number one i got chris teetering on his edge here before he drops into the concrete swamp so it's it's all precarious but we're trying to deal with that sun yeah i think we lost the sun the rest of the afternoon so all right we might uh actually know what we're gonna sw let's go back around here sure so anyway with while you're doing that uh the serpentine so serpentine is the mineral and serpentinite is the rock type made up of the serpentine and so you take one of those mantle rocks you bring it up to the surface or near the surface not all the way at the surface but within shouting distance of the surface and you add water uh that olivine is not stable in a low temperature environment the presence of water so it's going to start turning into that serpentine um and so serpentine that the name comes from i guess some people thought it kind of looked like snake skin you can get certain weathering patterns where you can actually see those individual serpentine minerals replacing the olivine grain so you can kind of get a mimic and that's something you really need to see under the microscope more than the the hand sample but it typically has that kind of waxy appearance sure there's quite a range of appearances it can be kind of a greenish sometimes more of a blue green you can get other low temperature magnesium-rich minerals associated with it a couple important things about the serpentine is one of course it's high water content but the other thing much much lower density than the rock that it started from so you add the water this stuff is now not this really dense stuff that wants to hang out down in the mantle it's it's much lower density and it can rise up higher in the in the crust uh given the opportunity it also tends to be fairly weak it's a fairly soft mineral that can deform so oftentimes you'll see these shiny surfaces where different pieces have moved past one another now are you i'm surprised at the moment if i'm getting what you're saying that that this or pentanite was originally mantle material that came up and we just added water but it was originally one of those peridotite guys most typically i really do have i mean you as i was saying you can get ultramafic composition occurring at crystal levels from let's say uh for example if we fast forward uh enough millions of years somewhere underneath the columbia river basalts we're going to eventually expose a big mafic ultramafic cumulative complex underneath so we know that that huge mass of lava on the surface that's only part of the story there's all the stuff that's left behind underneath and so we know a bunch of these olivines pyroxenes other minerals like that would have crystallized out at depth so there could very well be well almost certainly are compositions like that that are ultramafic composition but they formed at a crustal level um and those they're typically more of a recognized by a higher iron and titanium content compared to slices tectonically brought up out of the mantle and so of course those just because of that small compositional difference they'll still they can still turn into serpentine if you add some water okay rookie question from me it looks glassy it's got nothing to do with the water like obsidian has a glassy texture and it chills quickly that's totally not really so so the serpentine it's a fibrous or platy mineral there's actually different varieties of serpentine it's a sort of a family of minerals we don't need to get down into the weeds we'll just kind of keep it at serpentine for our purposes here um but similar to the reason that uh a rock with a bunch of mica looks shiny because those platy surfaces are all lined up reflecting the light so uh so it's typically quite fine grained as the other thing so you're not gonna see you know there's not uh gem quality serpentine that i'm aware of that you're going to go i don't have anything analogous to that nice epidote sample when it comes to the serpentine you can see them under the microscope um but hand sample it's just going to kind of look like a green shiny nice mass it's not all shiny sometimes it's it's not been sheared up as much and it's uh kind of a more solid looking uh appearance to it okay well i'm seeing a bunch of jade people on here right now okay so far have we dealt with anything in the world of jade we have not i've been kind of circling around it okay one more quick thing before we dive into the gym absolutely um before we leave the ultra mafic this is great chris keep it going keep it going this is actually a chromite nodule so most of those black minerals there are chromium so in some cases you get these pods of chromite it's very heavy and you also notice there's a nice bright green mineral in between yeah some of those grains so that's actually a chromium containing garnet there and again it's that chrome giving it that really distinctive bright green color of course we've lost our sun here yeah the sun's not coming back but we we're we're going to soldier through baby all right but i think that's i think that's good for the ultra mafic rocks if you got people who are excited about the jade then let's move on to that because that really connects the two pieces that we've just gone over good let me read this chris is doing a great job keep it going chris this is amazing wow can you imagine rock hounding with chris all right all right so we talked about what's happening to the mafic rocks in the subduction zone right we're going from the basalt to maybe a green shift to blushes into an eclegite uh and then we were talking about the mantle yeah and of course what is the subduction zone we're bringing those crustal rocks down to the mantle right right and so we're taking that oceanic crust yeah that basalt it's interacted hydrothermally with the ocean water i'm sure a lot of your your viewers have seen video footage of those black smokers and stuff you know that's kind of the surface expression of that whole thing so that's turning that basalt that would have started it out you know nice and pristine black and shiny at some point interacting with the ocean water turning it green uh so um that might be of the greenness thrust upon them category if you want to think of it that way so now there's water in there and that water is also getting down into the mantle as well and it's converting that peridotite so the peridotite or the dynamite those those were born green got it the serpentanite then i guess you could say had the the greenness thrust upon it interesting uh depending on your perspective um and then as we go down the subduction zone yeah we've got we've got these hydrated rocks we've added water to the oceanic plate so as it's going down we're increasing pressure and we're increasing temperature and those water-rich minerals that formed at low pressure relatively low temperature start to become unstable as we go deeper and those hydrous minerals the water containing minerals start breaking down into what minerals that have less water and well that fluid has to go somewhere so as we're going from the basalt into the blue shist into the into the eclide i guess you could say the the eklegite uh maybe attained greenness i guess um those fluids are going to rise up and interact with the overlying mantle um and that's where the jade comes in okay uh so i should mention there's two different types of jade jade people you're listening now perk up now come on get that notebook out so jade of course is is kind of a you know a gem term yes and the terms that get used in kind of the gemology world versus the geological world uh kind of have a little bit separate terminology but you might have heard the terms hard jade and soft jade or pyroxene jade and amphibole jade or jadeite jade and nephrite jade um so the real indicator here of the subduction setting is that pyroxene jade or the hard jade so oh he's got one ladies and gentlers um here's a sample oh down here um again you might notice that it's pretty dense uh rock there so jadeite is that pyroxene mineral in jade so if you want to be really technical about it that's a jaded type a jade is kind of hard to pronounce so we'll stick with jade here actually that's jada tight so what's distinctive about jade so it's a pyroxene mineral jadeite is a pyrrhic scene but it's a sodium containing pyroxene so it's got sodium and aluminum in addition to the silica in the in the pyroxene structure so unlike our normal pyroxene that you might find out of a basalt let's say that's primarily calcium magnesium iron this is sodium and aluminum so sodium and aluminum to me normally you think well that's going to be in a feldspar right that's going to be in that plagioclase feldspar that white mineral in mount stewart right that's where that stuff belongs that's where that stuff normally lives in the crust but at high pressure and moderate temperature that sodium that aluminum that gets dissolved in the fluid and those fluids are in coming off the slab it's taking sodium out of that out of that basalt it's also interacting with the ultramafic rock so that's a low silica uh mineral and so you can get jadeite precipitating in veins so that's what that sample represents so that came out of a vein a vein that was in uh hosted by sir pentonite so that's actually a sample from guatemala you can also get um jade that forms by transformation of pre-existing rocks so there's in the oceanic crust we talk about basalt but basalt basalt all the time but there there are some other things if you get down into the weeds so there are sometimes you if you're digging into the literature about ophiolites you might run into the term pledgio granite uh that was always a head scratcher for me i couldn't find it on any classification chart but it's pretty much quartz and and plagioclase it's kind of the very last little bit of the liquid that crystallizes after you've formed almost everything else so if you subduct that there's some um petrologic evidence that some of the jadeites form by transformation of that so you kind of form that composition first and then you subject it to high pressure moderate temperature conditions and oh thank you and seeking to adding water adding water perfect and you metasomatize it you bring in these these fluids and transform it into jade got it now the nephrite jade i haven't really dealt with that so much but that has a much wider range of formation environment so it isn't necessarily diagnostic particularly of a of a subduction setting but the jadeite jade uh which is actually quite rare there's not a huge number of localities in the world where you find that um and i i think it's on the order of you know 15 or 20 spots in the world where it's been described so george harlow who's a scientist with the american museum of natural history uh in new york is one of the real experts on uh jade formation and my colleague tatsuki tsujimori tohoku university in japan also studying jade formation processes nice so i believe the museum i know they had a display i i think they probably have some some good info i'm sure if you search for george harlow and the american museum you'll find a lot of good stuff and beautiful photos and so forth hey we got the sun for just a second is there something we want to strike while the iron's hot here on your thin section thing or something um oh yeah you know why don't we why don't we just jump over to that okay i'm coming back around we're going to try to go right into the sun and chris wants to try a little experiment with you all uh we maybe have the sun for a few minutes okay so nick you can tell me if we're if we're seeing things okay um is this kind of i might have to hold it okay maybe you can hold that okay so this is a thin section of the twin sister's dynite uh it probably looks pretty boring right now it does look boring i didn't want to say it chris but it looks boring you know maybe you can see a few blacks mix uh but what i'm gonna do here is i'm going to hold up a couple of polarizing filters with uh hopefully you can see it looks black going through there uh because there the polarization directions are perpendicular and i'm going to slide one above and one below oh um snap and if you can maybe it's easier for you to kind of rotate the the thin section around a little bit um but the way those minerals are interacting with the light and the polarization directions you get these beautiful interference colors and all of a sudden yeah oh i see yeah i want to get out of the shadow of the thing yeah yeah and so you can see uh yeah you gotta rotate the oh i see yeah it's kind of tricky i can do it yeah but you can you can see individual mineral grains and those different colors that you're seeing are related to both the mineral composition and the structure but also their orientation in 3d space so there's a ton of information in there um so that's what that twin sister's done eye looks like um when you cut it in a thin slice and of course you put this under a petrographic microscope is the real way to do it but this is just kind of the low-tech it's working baby they're loving it so this is like a kaleidoscope i'm dating myself now but please repeat why for those who have never looked on a microscope at minerals when you're rotating it on the stage like that why are we seeing different flashes at different times uh so it's because different mineral grains have different orientations okay so they're interacting with the light in different ways so basically light it's electromagnetic radiation that is interacting with the electrons in the atoms that are making up the mineral and how they interact is dependent on both the composition and the structure and so we can use that light as a probe of the atomic level composition and structure to tell us what it is but then we also have the context of all the textures the relationships between the different minerals in there that have a lot of information uh as well so anyway that'd be a whole different show yeah man um so this is the twin sisters donite that same green thing we were looking at a while ago like one of the first hand samples we had i tossed it somewhere right here yeah uh let me if you want to do a switch so we were just looking at a thin section uh i got to flip you around we were looking at a thin section of this guy and those minerals we were looking at had so many different colors but it's not like the minerals had different colors right it's um it's i guess the quickest analogy may be to think about um similar physical process to those rainbow colors you get on soap bubbles yeah or an oil slick on a pebble on a puddle it's it's an interference phenomenon so it's it's a totally different physical phenomenon from what makes the rock green when you look at it just with the naked eye i think it's official i think that worked okay well cool um yeah while we're still on the jade thing uh okay oh no no i want to still do the reverse so i'm flip come on larry come on larry oh just a couple of just a couple of dudes in the backyard playing with the oh what do we got here chris uh so the green there is another green pyrrhic pyroxene so this is this is a cut and polished slab this is actually from the alps in in italy damn uh and what's really interesting about that is we've been talking about mafic rocks we've been talking about ultramafic rocks we've been talking about oceanic crust and mantle and this is what happens when you stick a bit of continental crust down a subduction zone so that's started out life as a granitic composition so continental crust really went down the subduction zone to quite high pressure and moderate temperature and again granite's got those feldspars in there that have that sodium and aluminum in there you get it down deep enough you end up with that green pyroxene that jade in there and uh some other uh other minerals uh that recrystallize at the higher temperature uh conditions so that's actually from a quarry where they're cutting and polishing this stuff and selling it as building stone so i was at a conference there a number of years ago and so sometimes at these conferences i'll give you a little rock sample of something that's of note from the local area and so i just grabbed that one beauty that was a fun one and then if we want to just quickly do one last one this one's kind of a crazy crazy one but this one right here this is actually different but also related to what we've been talking about uh so in this case that bright green mineral is a chromium-rich uh mica starting to lose the sun there um meriposite or fuxiate is also i think maybe the approved term now oh that's great for geological jokes yeah but uh this is from sorry patrick california gold country um so it's bright green because of chromium the chromium came out of ultramafic rocks out of serpentinites and then it's and then you can see some pyrite in there and and there's some quartz and so this is associated with some of the gold mineralization in the in the california gold country but since this the topic was green i had it sitting on my shelf uh and so there there is kind of a tangential connection to our main theme here which is oceanic crust and and mantle yeah so uh yeah oh love it love it boy take a breath man take a breath i love it um it is approaching the top of the hour i wonder let me flip you around i don't know if you feel like doing anything on the chalkboard but at least help us i don't think we know what an ophiolite is yet right we haven't gotten to that yet shoot and can we do it graphically i don't know if we really need more hand samples graphically would be great get that blurry shadow out of your way here let's see okay so i think we'll use this one that you've got here so we've got our our oceanic crust is this supposed to be hawaii sitting on here not necessarily any kind of spreading ridge or okay spreading ridge is good so we're talking spreading ridge not hawaii um but ophelite i don't know how far that term goes back but some of you might have encountered this this term the steinman trinity of association of serpentinite with basalt or green schist um and then deep ocean sediments so classically chert right so what is that association so we've got altered mantle basically we've got basalt and then we've got these sediments that had to form very far from a continent where you're not getting any sand or silt or anything where it's pretty much just dead critters drifting to the bottom of the ocean floor and so the interpretation is you get these plates spreading apart yep um so we've got the mantle coming up plates moving apart here as part of that decompression you got hot mantel you bring if you bring it up quickly enough to the surface remember the heat takes a long time to get in or get out so it stays hot and you've released the pressure and it melts when you get when you get to shallower pressure so that's where your basaltic magma comes from that's forming your pillow basalts right remember our popcorn pillow there sometimes you also get what are referred to as sheeted dikes so that's where uh the crust is pulling apart the lithosphere is pulling apart and you get that magma rising up it fills it up it it makes a dike you split that dike apart you put another dike in there so it's just basically dikes going into dikes going into dikes there's no you know our normal thing you look at the tiana way dikes right there's a dike and then there's some wall rock that's different right but here is just one dike after another because you just keep pulling on that cross pulling pulling pulling pulling you know you might have thousands of kilometers of extension going on there over the life of of uh one of these things if it's really long-lived you don't always get that sometimes sometimes the magma supply is not that that much and then you've got the mantle underneath so you've got the mantle down here you've got your basalt and then after this stuff forms as this is drifting away from the spreading ridge then you're just very slowly accumulating those deep ocean sediments so if you have those radial area those those uh critters that form a silica shell they're photosynthesizing you're floating up at the surface of the ocean they die they sink down to the bottom you get a salicious ooze down there as that gets buried that amorphous silica which forms the little shell gradually transforms eventually into quartz fine grain quartz producing your chert some of your viewers might have heard of iron manganese nodules down in the deep ocean so commonly these things have a higher manganese content to them um but indicating form far away so that's kind of the classic ophelite association which is what so it's kind of a suite of rocks and ophelia it's a suite of rocks so it's not one rock it's not one mineral it's an association so deep ocean sediments yeah shirts basalts of some variety right uh and then serpentinite okay uh is kind of that classic association and so that was way back in i don't know 1903 or something that that i think that diamond trinity i maybe one of your viewers knows something more accurate about that but it really wasn't until plate tectonics came along that people started thinking making the connection between ophiolite and oceanic crust and so there's kind of a classic 1972 penrose conference gsa uh definition where you had those those deep marine sediments you had the pillow basalts you had the sheeted dikes you had layered gabras isotropic gabaras so basically this is all basalt of different things i'm sure you've you know you look in any intro geology textbook you're going to find something like that and then underneath you have the mantle and more recently people have appreciated much more that there's quite a variety of products that can come from a spreading center so that's one of them but that's really more a fast spreading oceanic spreading center like the east pacific rise yes moving apart pretty fast you're cranking out lots of basalt you're moving that mantle up to the surface fast it's pretty hot when it gets up close there large volume of basalt but you look at areas where the spreading rate is much much slower you don't get so much basalt so you tend to get these pods of basaltic composition so like a gabbro or something uh and then you get tons of serpentinite even serpentinite exposed right on the oceanic floor um exposed along faults and so forth so there's there's a variety but if you look back in the older literature um people times a lot a lot of times would try to fit everything into that 1972 classic penrose stratigraphy and they'd kind of be grabbing different things and trying to reconstruct it and sometimes of course that's the case it really did start out that way and it got dismembered by faults later in other cases it probably probably was one of these more slow spreading ridge type scenarios and maybe you never had some of those pieces uh there to begin with well this is fascinating and i think i'm gonna ask a question that's my own question and it's going to transition us to live q and a with everybody else if you're okay so my question is especially if we look at that thing right there and it's totally an ocean floor situation we might be a thousand miles away from the nearest continent let's say why didn't all that stuff go down a subduction zone why do we have any deep ocean stuff up here above sea level excellent question and the answer is almost all of it does go down the subduction zone very little of it gets preserved same thing especially for the blue chest and the eclejoid i mean that's why they're they're widely distributed rocks but they're not things that you see in massive abundances i mean if you think about the ocean floors are you know 70 percent of the earth's surface it's like well that stuff all went down in subduction zone at some point why isn't it 70 percent blucious necklace yeah uh and the answer is it's it's more dense than the mantle most of that stuff just gets recycled um and never comes back well i shouldn't say never comes back it comes back but in greatly transformed you know we see little little whiffs of it in the chemical or isotopic signature of basalts that are coming up to the surface or you see it geophysically way the heck down there or you see it trapped inside a tiny diamond inclusions but it's dense it doesn't want to come back up so it's unusual circumstances you get a little bit of it and it pretty much comes down to buoyancy gravity so how do you get a dense rock up to the surface well you either make it less dense so you take the the mantle rock and you add water and you turn it into serpent night well now it's it's not so dense anymore it doesn't want to go back down into the mantle right um or you surround it by lower density rocks so uh where you get these eclejites and blushes you don't just have that stuff mile after mile after mile and nothing else they're associated with lower density rocks so they're embedded in a melange of serpentonite or maybe a sedimentary rock a shale or a gray wacky in some cases you have continental crust that are hosting these things and that gets down there but it's it's not as dense as the mantle and eventually some of it is going to want to come back to the surface it's more buoyant and will come back up so the answer is most of it does go down but uncertain circumstances we can actually scrape some of it off in one way or another love it love it okay we're switching to you guys and i'm gonna get chris started with the first question i'm gonna go in and get some coats and some hats do you need it i'm doing good actually oh man i guess i'm i'm not in wisconsin anymore i'm getting wimpy so you know i i pi you know i put on my long underwear and i brought a bunch of coats because it's so cold yesterday and then it was all nice and sunny it's like hey this is great okay so i'm going to read the first question from you guys and then i'm going to run in real quick and get some clothes chris is a man he's a man's man so he's in good shape california you've developed some thick skin i can at least get you some hot water in your mug um so you know the drill uppercase for your questions and um zig star has our first question are there different products in deeper subduction i.e marianas versus juan de fuca uh okay so uh so yes and uh i was alluding to that a little bit um marianas again that's old cold pacific plate uh so that's as it cools and i should mention it's not just that basalt but it's the the mantle lithosphere underneath it gets cold and therefore denser so high density it's going to sink back into the mantle more rapidly that means you're going to maintain low temperatures down to higher pressures whereas our example here in cascadia ridge is not that far offshore so the the crust is not very old in other words it hasn't had much of a chance to uh cool off and then it's also subducting fairly fairly slowly so that's more chances for the heat to come in so you're going to get a higher temperature at a given pressure so marianas you're going to do lots of blue shifts low temperature eclegites uh whereas here um probably not a whole lot of blue shist in the in the cascadia subduction zone today uh more green shifts uh and so forth um i guess uh since uh up here comes nick all right here we'll do a switcheroo excellent thank you from some viewers in seattle perfect okay you ready for another question you know i did see a question scroll by that i would like to answer somebody asked why are these things green good good good and uh so color and minerals there's lots of different causes of color and minerals um but again it comes down to how the light remembering the light is electromagnetic radiation um and it's interacting with the atomic level structure of the mineral so pretty much what's happening is in a simplified terms the color that you're seeing you know the the light coming from the sun or from your light bulb it's all spectrum of different colors right so you can split it out in a prism some of those colors are going to get absorbed by the mineral so different color equals different energy that means it's interacting differently with that atomic structure the mineral and so it comes down to structure and composition in terms of composition i mentioned chromium a number of times those were those were examples of chromium it's typically that first row transition metals on the periodic chart so what's the most common of those iron so the usual answer for most things why is it green why is it red why is it pretty much any color than white is iron most of the time but not always love it you doing okay you want to go a few more minutes here oh absolutely okay um automatic scroll good sandy asks is there a good example of sheeted dikes in washington ooh uh you know i'm not familiar enough i i would imagine people probably looked at that in the angles complex or maybe up in the san juan islands yeah uh but i'm not sure fine uh kyle what are the processes that bring mantle rock to the surface same question for subducted plate excellent question uh so main categories are uh pretty much either subduction plates coming together and you're sticking some crust down there the water is coming up and hydrating actually i should maybe do this on the chalkboard yeah do it here actually so we've got fluids coming up from that crust so so over here when you're deep enough you're melting you're forming magmas you're getting your chain of volcanoes but out here in this mantle wedge it's it's too cold to melt so those fluids are going in there converting that mantle rock into cerpentinite which is low density some of that can make its way up there's some little serpentinite diapers so basically mud volcanoes this repentant night out in the four arc of the marianas islands would be one example so that's where you've added water at depth it's become low density and you've actually carried some of it up to the surface the other thing of course is if you shove some continental crust down this down this trench you can tectonically insert some mantle and because that continental crust is buoyant some of that's eventually going to come back to the surface and you bring it up that way you could also imagine if you have uh some of this rock here kind of getting bulldozed up on the on the top of the snow plow so to speak and you have addressed why it's green why ocean rocks are green peter says which is the deepest green rock we can usually see oh well i guess it depends on your definition of usually i guess we could talk about deepest green rock that you could see that we know of at all ever we do actually have our deepest record of actual physical samples from the earth's deep interior that we know of today are tiny inclusions inside of diamonds uh so one thing that's really interesting is that subducted oceanic crust it keeps going down down down well you get below uh you know 120 150 kilometers you're in the diamond stability field so we don't we haven't talked about carbon there's not not normally a lot of carbon in these rocks but there is some and so you can those diamonds form down there and they're actually trapping little bits uh little tiny minerals and so some of those minerals they're trapping are actually eclegitic minerals so garnets and pyroxenes and the deepest ones that have been recovered so far actually out of the lower mantle uh so there's out of the mantle transition zone but some of them even deeper than 660 kilometers depth so that's the deepest thing we know of ever in terms of the deepest thing you could see commonly uh well around here you've got that french cabin creek blue shift screenshots that's pretty deep um if you're down in california there's eclogites associated with the franciscan complex those would be those would be deeper there's even one little you know barely eclagite that ned brown worked on years back and uh sean mulcahy at western has been poking around there more recently there's uh you've been talking about the yukon tanana terrain a little bit there's eclogites up there pretty high pressure um so there there's actually quite a few of them scattered around but they're they're not highly abundant rock so uh depending on yeah what you think of as most common uh you kind of just touched on this but price wonders are there direct associations with specific green rocks and specific terrains and i'm going to kind of be doing that next time but are there specific exotic terrains that you can think of immediately that are full of these green rocks uh well you've been talking a lot about these oceanic terrains so anywhere you got a lot of basalts a lot of serpentinite i mean pretty much that's looking oceanic plateau uh ocean cross something like that so that'll be the short answer s gudgel and i have a question i'll combine my question with yours s is soapstone a form of serpentinite and my part of that is are you as hung up as i am on calling something serpentinite versus serpentine oh good uh good question um i guess yeah at the end if we want to loop back the whole terminology thing we could throw that in there so so soapstone um you know it's it's not a formal geological term but it's you know kind of anything soft i mean i think of it as talc yes a talc rich rock and so talc is a magnesium-rich very hydrous silicate mineral mineral that you can get as part of the serpentinization process um you know there's some other environments that do form talc as well i should point out um so uh it remind me the question again well that's the soapstone and then i'm wondering you know some people call it serpentine even though i i call it sir penta night i mean what's the difference serpentine is the mineral and serpent knight is the rock i would say for our purposes i kind of use them interchangeably i wouldn't get hung up on it good one less thing to get hung up on nice job muffler boy okay um gary asks how does migmatite fit into this model oh we have not turned talked about magmatite so magnetite is high temperature okay so that is literally mixed rock uh so you've got silicate melt and you've got some solid stuff so it's kind of on the boundary between igneous and metamorphic so everything we've touched on here is is much lower temperature than that yes and that's your wheelhouse you're up in chelan and the migmatite and you're doing some current research further north than that i mean so we might at some point well but not really into our green uh discussion today uh toughen up fluffy asks are these all accretionary wedge minerals or do you also find volcanics uh in terms of the green stuff i'm in a creationary wedge that would be you'd be scraping off uh altered basalt from the oceanic floor you'd be scraping up bits of serpentonite uh so of course the basalt is a volcanic i mean you can certainly add water to mafic or intermediate composition volcanic rocks like volcanic arch rocks you can get plenty of green rocks there too we haven't really been touching on those but i'd say anything that is mafic or intermediate composition igneous rock and you add water it's going to turn green to some degree or another got it how about a few more and we're done chris breeze is picking up again i'm i'm wimpier than you are uh ben wonders if you could explain the difference between peridotite and olivine i think you did but can you so olivine is the mineral peridotite is the rock and it's it's kind of a a category of different rocks in there that includes donite versus peridotite there's webster right harper guide other terms in there that we don't really need to dig into but all beans the mineral peridotite is the rock david says is the cold dense crust the reason why the marianas trench is so deep compared to other trenches uh that and also i think the fact that it's so far away from a sediment source because you form a trench you know you dump sediments into it but if you don't have any source for it but but definitely the fact that it's very old cold lithosphere uh is is why it's so deep there but also because we haven't filled it in with other stuff i'm getting a bunch more questions about the green color would you mind one more just a couple sentences about why these ocean rocks are green well the composition basically so if you have a mafic or an ultramafic composition plenty of iron in there and it's really in each of these minerals in the chlorite in the actinolite in the epidote in the olivine and the serpentine it's the presence of iron in all of those things that's giving it the green color uh that we're seeing thank you gary can you get a blue serpentonite you know some of them do have kind of a bluish tinge to them i noticed as the questions are getting shorter so maybe you've had enough too just kidding we'll do three more how about that okay tony from whitewater wisconsin that's my whole turf tony what are the green minerals commonly found in agates in the pacific northwest are there green minerals in agates oh you know i'm not as familiar with that i mean in agate you're typically filling in some kind of a fracture or vug [Music] in some other rock i don't have any off the top of my head but that isn't not something i've really studied much good let's finish with an easy one what are the classes that you commonly teach at central and what kind of research are you doing with your students ah so in terms of classes that i normally teach so uh kind of big picture normally i would teach a rocks and minerals class so kind of that's the first lab class where students get to actually learn about identifying minerals and rocks and and what we can actually interpret from them so taking at the next level beyond the intro a teacher mineralogy class i'm going to be teaching that next quarter so we get to learn how to use the microscopes dive into things a bit more detail kind of think about the atomic level properties and chemical bonding a bit of thermodynamics and some of the interpretation stuff and then i do a couple elective class so a photography petrogenesis class where we really dive in to how to read these things kind of more as a research tool uh do a geochronology class so those are kind of the main ones and then in terms of current research um i've been working on the chelan migmatite complex i've got some work going on there done for quite a few years a lot of work on very high pressure rocks eclodrites and associated rocks uh mainly over in china and then my two newest students uh one of them is going to be working on some local rocks the monash dash inlier that you've been talking about so we're kind of the vicinity where that blue shish came from and then my other student is actually doing a method development project uh in the lab so developing some lab methods here for for doing some of the analyses and for a few of our hardcore fans who know a lot of the research going back decades they know the name mattinson from the 1970s and even the 1960s that isn't you is it no so my dad did his phd here in the 60s and and he really did the first modern geochronology in the in the north cascades uh so that citation still pops up here and there so jim mattinson is associated with with with which uh terrains are with which rocks oh gosh you know he's uh worked all over i mean certainly worked a lot on the shelian magmatite complex in particular but uh did a lot of the dating uh in there and uh you know name pops up so soaking nice the dumbbell uh marble mount uh plutons and uh did a lot of work over the years coast range ophelite down in california working clamas things like that nice will your dad be watching this do you suppose uh well no his his health is not not doing too well right now so okay all right well one quick little last look at our uh board and our revisit of our two goals for today and then we'll get to a toast so i don't know chris did we hit everything here uh the green stone um sharon from colville had a green stone for us you know i could quickly comment on that run in here sure greenstone versus green schist i tend to use green stone to refer to the sub green shift part of the uh the pt diagram so we don't quite get up high enough p and t but you know lots of things that are in the green species in terms of pressure and temperature they don't actually have a they don't look very shifty yeah um so i would say for for this audience i wouldn't worry overly much about the difference between them okay well we hit pretty much everything else i'd say and i hope that you feel like we accomplished a few things for you and answered a few of your questions um a toast to you and do you want to show off your gauge oh that's right we didn't uh we didn't even do this in case you're wondering how we actually measure pressures uh in these rocks you know you just took this thing up and uh nick do you have your meat thermometer oh i forgot it oh well anyway you just stick a thermometer in you hook up the pressure gauge no it's it's not it's not that simple but by measuring the composition and looking at the types of minerals you can calculate what the pressures and temperatures these things are quantitatively good thank you so here's one of the many wines that julie dropped off last sunday and uh i enjoy this one so chris so chris and i want to toast you step in the frame chris can you see yourself there we go so here's to you cheers mmm delightful good way to end the show kind of a hint of ultra mafic there here's to your health the health of your family and friends would you like to offer a toast here's to all the green rocks aficionados out there you know when dick nick told me the title of this show i thought geez nick you may as well call this rocks only a mother could love but uh it seems like we got some excited folks about this i think we do here's steve okay let's look at the schedule for next time thanks to chris for his amazing information and hopefully digestible to you you are welcome to come back here in the backyard or the front yard or the front porch i have no idea but we will be back to the business of dissecting a few more terrains on the east side of a very famous fault that will go unnamed although many of you know it already so next time we will be in the eastern foothills of the cascades and then i've actually thanks to pencils by patrick have been culling like a madman upstairs and i've got the next half a dozen shows figured out now as we kind of cruise through much of the north cascade which is really the meat and potatoes of this whole thing so we're finally to the hornet's nest and i have a rough plan and hope to continue to kind of put that plan together so until next time one more time for chris and myself here's to you and thank you for tuning in thank you i love you and goodbye

Channel: Nick Zentner

Views: 14,310

Rating: 4.9472294 out of 5

Keywords: Nick Zentner, Nick From Home, Chris Mattinson, jade, serpentinite, jade hunters, ophiolite, metamorphic rock identification

Id: Nj7Qato3bZw

Length: 99min 50sec (5990 seconds)

Published: Fri Nov 06 2020