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just like jessa done i'm also a my

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background is in or geology and so what

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I'm hoping to do is take some of the

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techniques that we use in our field and

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kind of apply them and some of the very

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different approaches we have to looking

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at geology and see what can that tell us

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in the astrobiology field so again I we

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have a lot of corporate sponsors mostly

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because they let us access to their

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field site so right so to start off I'm

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going to be talking about our key and

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sulfate in particular and so I'm talking

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about our kyun I'm talking pre 2.4

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billion years and this is the big

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disclaimer alert so some of the earlier

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talks you've heard about the great

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oxidation event the rise of oxygen at

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2.4 billion years I do not fall under

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that school of thought and so what I'm

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actually presenting here is showing some

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of the techniques and actually one of

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the ways we've gone through and done

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some modeling to kind of say why we

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don't put that rise of oxygen and

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particularly some of these other

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interesting redox-sensitive elements why

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we don't believe that balls at 2.4

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billion years so in particular I'm going

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to be talking about sulfate we care

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about sulfate very important for biology

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very important for a lot of the redox

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chemistry that we're interested in and

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really important for making shiny medals

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so current consensus right now is that

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if you have this an toxic archaean it's

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really hard to have sulfate

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concentrations greater than about point

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1 millimolar that's based off of things

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like sulfur isotope evidence that use

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just simply if you look at the archaean

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it should be hard to get that sulfur

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Delphic concentrations greater than that

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however we start looking at the actual

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geologic record there starts to be some

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major problems first and foremost this

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is the dresser formation it's 3.44 nine

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ish billion years old it's a multi

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million metric ton barium sulfate

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deposit and that's very hard to do if

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you have very little sulfate in your

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oceans doing the calculations if you

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take about that much it requires almost

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an entire world's ocean to evaporate to

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make that much of a bedded salt bed so

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that's one problem the other thing is

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from our actual or deposit itself i'm

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working on a hydrothermal system that

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i'll get into but we also have lots of

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barite in our stuff

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so this is an ex RF image the green

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sections is where we're going to be

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seeing that barium sulfate and you can

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see it's not equal to PI right so

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there's some interesting fluid chemistry

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of evolution kind of showing up there so

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in particular i'm interested in

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volcanogenic massive sulphides VMS

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systems unlike justice system where it's

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actually dealing with magma getting some

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exposure our system really doesn't

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actually make real contact with any

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liquid rock it's just heat that's

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percolating through sea floor so the

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wave EMS system works there analogous to

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the black smokers that everybody has

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been talking about what's happening is

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you're actually have ocean sea water

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percolates through fractures in the rock

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as its fracturing through there's some

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intrusive body be it a dike via the

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mid-ocean ridge setting something like

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that that's generating amount of heat

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that's going to actually drive that

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water through get the big circulation

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and as that water moves through we get

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all kinds of interesting reactions some

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are just simply moving metals actually

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making the massive sulfide that we're so

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interested in mining but some of the

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other stuff is actually doing

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interesting redox chemistry so one of

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the very very important reactions for

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VMS systems it generates a lot of the

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sulfide that's actually in that massive

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sulfide is seawater sulfate as it comes

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in contact with ferrous iron in these

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rocks at above 250 degrees if there's

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lots of ferrous iron which these are

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basalts that ferrous iron will actually

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become ferric iron in that seawater

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sulfate will actually become sulfide and

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so when you get that mutual

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thermochemical sulfate reduction you

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actually will get halos where you

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actually get some amount of increased

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ferric iron in this rocks and you'll get

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lots of sulfide in return so the actual

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site that I'm interested in it's known

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as the panorama district we're way up

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here in the far north western end of

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Western Australia the actual district is

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actually a cluster of multiple VMs

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systems and what's beautiful and really

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rare about this is it's actually cut on

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profile so usually when you're looking

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at these deposits unless you're actually

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in a mine you don't get to see what the

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circulation cell looked like but in this

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case if we actually look at this track

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column we would have laid down the

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basalts and everything like that that

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was being circulated through first and

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then this big straily granite pumped up

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through and as it did so it tilted

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everything about 90 degrees and that's

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really the end of where the main

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formation stopped so we actually have

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this beautifully preserved side view of

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these systems so we can actually look at

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the hydrothermal circulation cells now

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what's also important to know for it's a

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geology we get the obligation you know

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to show a field work photo what a mining

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company describes as a road is somewhat

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different than but you might describe as

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a road so it's an interesting place to

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do fieldwork and collect samples so what

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we've done though is we've actually

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collected large amounts of samples and

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we've analyzed them prepare at Ferris

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ratios so right this is kind of weird

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right we're going to be looking for

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sulphate concentrations but we're using

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iron well we're coming back to that

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actual reaction that we were talking

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about that's so important in VMs systems

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now we think we actually have a pretty

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good handle on VMS systems when we work

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with ore deposits because there's so

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much money in the line we understand

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them pretty well and we're pretty sure

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we actually have a good handle on not

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only the processes the temperatures

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involve the reaction rates that are

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involved so we think we can actually do

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a lot of modeling going forward so if I

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have a map like this where I've actually

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been able to say that yes there's

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actually an increase in the ferric

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various ratios around what we've

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actually deemed and a lot of authors

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have worked on and identified as the

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hydrothermal circulation cells but maybe

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we can actually use this barrack faris

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enrichment to actually say how much

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sulphate was required to circulate

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through the rock and therefore what was

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the seawater sulfate concentration so

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alteration geometry fortunately like I

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said we have this nice profile view so

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what we actually can do is we can kind

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of confine these slabs and if we do a

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simplified strat column most of our

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circulation occurred in these anti site

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basalt layers they're roughly tabular

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and frankly for it being 2.4 we're going

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to start assuming some simplified

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geometry it's something we do for a lot

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of a lot of these type of or systems

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it's we take simple shapes so in our

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case we chose a cylinder it's a fairly

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simple it's a fairly accurate assessment

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for doing these type of things we've

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done them for a lot of these types of

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ore deposits so what we're doing is

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we're going to assume a cylinder our

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circulation cells about 6 kilometers

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insert in diameter and so that cylinder

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of rock has some starting ferric very

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she o in our case we took pristine

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back-arc base and basalt that has a

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ferric various ratio of about point two

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it's a pretty fair assessment people

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have done a lot of identification on

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these basalts starting off with that

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it's an assumption but it seems like a

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pretty safe assumption is that's what

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our starting iron oxidation state is so

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what's going to happen is more and more

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sea water is going to circulate through

202
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this rock as time goes on and as as

203
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that's happening you're going to

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actually start increasing the iron

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oxidation state so from the actual data

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that we've measured we have a final

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faris ratio of about 2.5 so what we've

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actually done is we can say to get from

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here to here we have some huge number of

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moles of iron oxidized alright the

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number is not as important but we need

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it for our calculations so if we go back

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to our favorite reaction here what we

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can do is we take the number of moles of

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iron that we're actually oxidized we can

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come back and derive out how many moles

217
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of sulfate were required now that gives

218
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us a total amount of sulfur that does

219
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not actually give us actual ocean

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concentrations to do that we actually

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need to start thinking about how much

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00:07:45,589 --> 00:07:42,779
would actually have to flow through the

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rock so when we do these hydrothermal

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systems just using the shear volumes of

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rock really cumbersome and bulky and

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doesn't make a lot of it doesn't work

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really well in your head so what we use

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is what we call water Rock units so what

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a rock unit is the mass of water to flow

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through the same mass of rock so just an

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00:08:03,260 --> 00:08:01,020
easier unit to put your head and so we

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notice is and as you might expect that

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at very low sulphate concentrations it

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takes more units of this water at low

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sulphate concentrations to flow through

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it to generate that person that observed

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alteration however if we start

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increasing that sulphate concentration

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now it's certain to take smaller and

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00:08:23,450 --> 00:08:21,149
smaller water Rock ratios now we're

241
00:08:25,879 --> 00:08:23,460
starting to actually can we kind of

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limit it in so again that doesn't

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actually this chart I have this

244
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highlighted but I'll show you why if we

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actually go to the actual deposits and

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we start looking at the alteration

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00:08:37,579 --> 00:08:35,640
minerals it's really nice as we can

248
00:08:39,980 --> 00:08:37,589
actually say how much water has flown

249
00:08:41,420 --> 00:08:39,990
through there at temperature so when we

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00:08:43,969 --> 00:08:41,430
actually look at the alteration minerals

251
00:08:46,579 --> 00:08:43,979
we can say that there was probably not

252
00:08:48,470 --> 00:08:46,589
more than 60 water Rock units flowing

253
00:08:50,060 --> 00:08:48,480
through that body they're simply the

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00:08:51,860 --> 00:08:50,070
Clay's and the things we see there if

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00:08:53,509 --> 00:08:51,870
you had more water flowing through it at

256
00:08:55,100 --> 00:08:53,519
higher temperatures you simply would not

257
00:08:58,370 --> 00:08:55,110
have preserved the mineral textures we

258
00:09:00,680 --> 00:08:58,380
see so using that as our limit well we

259
00:09:02,600 --> 00:09:00,690
see that just based on the hydrothermal

260
00:09:05,330 --> 00:09:02,610
alteration that we have a limit of about

261
00:09:07,280 --> 00:09:05,340
one millimeter the water that was

262
00:09:08,540 --> 00:09:07,290
flowing through these systems now

263
00:09:10,730 --> 00:09:08,550
there's another way we can go about

264
00:09:12,860 --> 00:09:10,740
looking at this I'd mentioned that these

265
00:09:14,990 --> 00:09:12,870
hydrothermal systems these VMs deposits

266
00:09:19,130 --> 00:09:15,000
are driven by some sort of intrusive

267
00:09:21,440 --> 00:09:19,140
heat body so if we take again our nice

268
00:09:23,660 --> 00:09:21,450
simplified cylinder there there needs to

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00:09:25,370 --> 00:09:23,670
be some volume of intrusive below it

270
00:09:26,960 --> 00:09:25,380
that's supplying the heat that's

271
00:09:29,360 --> 00:09:26,970
actually going to be driving the system

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now Larry Catholics who's done a lot of

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work on these systems he's done all the

274
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very very complicated math but it really

275
00:09:37,610 --> 00:09:35,130
comes down to at the end of the day to

276
00:09:39,290 --> 00:09:37,620
heat 1 kilogram of seawater to 250

277
00:09:41,150 --> 00:09:39,300
degrees which is the requirement for

278
00:09:44,210 --> 00:09:41,160
this reaction to go forward you need

279
00:09:45,980 --> 00:09:44,220
point seven kilograms of melt so if we

280
00:09:47,510 --> 00:09:45,990
go back to looking at the actual water

281
00:09:50,090 --> 00:09:47,520
Rock ratios that we were talking about

282
00:09:53,240 --> 00:09:50,100
depending on sulfate concentrations we

283
00:09:55,370 --> 00:09:53,250
can actually say how thick of a the

284
00:09:58,670 --> 00:09:55,380
volume of melt has to be to actually

285
00:10:00,500 --> 00:09:58,680
drive this hydrothermal cell so if we're

286
00:10:03,140 --> 00:10:00,510
at sulphate concentrations less than say

287
00:10:05,420 --> 00:10:03,150
five millimolar you all of a sudden need

288
00:10:08,600 --> 00:10:05,430
a granitic intrusive that is now more

289
00:10:10,040 --> 00:10:08,610
than 10 kilometers thick well we've

290
00:10:11,690 --> 00:10:10,050
mapped and we've drilled the surly

291
00:10:13,640 --> 00:10:11,700
granite we know it's not actually larger

292
00:10:15,350 --> 00:10:13,650
than 10 kilometers thick so that right

293
00:10:17,570 --> 00:10:15,360
there is actually providing a limit that

294
00:10:20,150 --> 00:10:17,580
you needed to be able to actually flow

295
00:10:23,060 --> 00:10:20,160
water through this body and not quench

296
00:10:25,460 --> 00:10:23,070
the system so that's a suggesting that

297
00:10:27,560 --> 00:10:25,470
we're at least five millimolar sulfate

298
00:10:33,320 --> 00:10:27,570
in this contemporaneous arc en seawater

299
00:10:34,970 --> 00:10:33,330
now that's assuming at 250 degrees if we

300
00:10:36,110 --> 00:10:34,980
base on some of the metals that we see

301
00:10:37,910 --> 00:10:36,120
there are things like copper that

302
00:10:39,050 --> 00:10:37,920
require higher temperatures odds are

303
00:10:40,790 --> 00:10:39,060
we're actually going to probably move

304
00:10:42,770 --> 00:10:40,800
this even towards greater sulphate

305
00:10:45,950 --> 00:10:42,780
concentrations in this contemporaneous

306
00:10:47,090 --> 00:10:45,960
seawater so really what did we really

307
00:10:48,980 --> 00:10:47,100
see when we're going through these sites

308
00:10:50,630 --> 00:10:48,990
the first thing and foremost is if

309
00:10:53,180 --> 00:10:50,640
you're interested in are keen sulfate

310
00:10:55,460 --> 00:10:53,190
there's extensive sulfate mineralization

311
00:10:56,960 --> 00:10:55,470
it's all barium sulfate but frankly if

312
00:10:58,430 --> 00:10:56,970
you think about things like gypsum there

313
00:11:01,070 --> 00:10:58,440
to soluble they would not have been

314
00:11:03,290 --> 00:11:01,080
sitting around for 3 billion years we've

315
00:11:05,120 --> 00:11:03,300
observed very large ferric enrichments

316
00:11:07,130 --> 00:11:05,130
and they seem to be the result of

317
00:11:08,540 --> 00:11:07,140
sulfate reduction and when we looked at

318
00:11:10,220 --> 00:11:08,550
the actual alteration patterns in some

319
00:11:11,990 --> 00:11:10,230
of the thermal modeling we actually see

320
00:11:14,540 --> 00:11:12,000
that we're probably looking at at least

321
00:11:15,800 --> 00:11:14,550
125 millimolar zuv sulfate

322
00:11:19,100 --> 00:11:15,810
which is an order of magnitude greater

323
00:11:21,530 --> 00:11:19,110
than what people are proposing that

324
00:11:23,780 --> 00:11:21,540
should exist in that pre rise of oxygen

325
00:11:26,030 --> 00:11:23,790
archaean now kind of a teaser something

326
00:11:27,110 --> 00:11:26,040
I'm not presenting here yet but if we

327
00:11:28,970 --> 00:11:27,120
actually look at some of the other

328
00:11:31,430 --> 00:11:28,980
elements things like uranium tungsten

329
00:11:33,920 --> 00:11:31,440
chrome that are also redox-sensitive we

330
00:11:36,019 --> 00:11:33,930
actually see similar patterns to what

331
00:11:37,610 --> 00:11:36,029
we've seen here for the ferric ferric

332
00:11:40,250 --> 00:11:37,620
iron so it's not something that's alone

333
00:11:41,780 --> 00:11:40,260
in a vacuum and so I really like the

334
00:11:43,790 --> 00:11:41,790
idea yesterday of doing this takeaway

335
00:11:45,410 --> 00:11:43,800
message and really the takeaway message

336
00:11:46,610 --> 00:11:45,420
that I have and it's not just from this

337
00:11:48,949 --> 00:11:46,620
site but it's also looking at things

338
00:11:50,750 --> 00:11:48,959
like the banded iron formations that are

339
00:11:52,340 --> 00:11:50,760
all over Australia and some of the other

340
00:11:53,810 --> 00:11:52,350
interesting chemistry of these VMS

341
00:11:56,840 --> 00:11:53,820
systems not just in Australia but also

342
00:11:58,819 --> 00:11:56,850
in Canada it's increasingly looking like

343
00:12:02,000 --> 00:11:58,829
the archaean ocean chemistry at least in

344
00:12:04,639 --> 00:12:02,010
the redox element state is actually a

345
00:12:07,610 --> 00:12:04,649
lot like the modern ocean that at least

346
00:12:09,440 --> 00:12:07,620
the rise of oxygen as we know it might

347
00:12:11,990 --> 00:12:09,450
not have happened at 2.4 there obviously

348
00:12:14,090 --> 00:12:12,000
was a rise of oxygen but we need to do a

349
00:12:16,370 --> 00:12:14,100
little bit more fine-tuning as to

350
00:12:19,519 --> 00:12:16,380
exactly when it was and can we make a

351
00:12:21,290 --> 00:12:19,529
cyst can we choose a date that includes

352
00:12:23,510 --> 00:12:21,300
a lot of the geologic evidence that kind

353
00:12:33,319 --> 00:12:23,520
of stands as a major impediment to

354
00:12:48,790 --> 00:12:33,329
putting it at 2.4 thank you nicely done

355
00:12:56,140 --> 00:12:55,040
right so back urk basin basalt the

356
00:12:58,460 --> 00:12:56,150
reason we've chosen backward-facing

357
00:12:59,840 --> 00:12:58,470
there's actually been a lot of geologic

358
00:13:01,820 --> 00:12:59,850
work on this site because there are two

359
00:13:03,200 --> 00:13:01,830
economic grade and when people have

360
00:13:05,660 --> 00:13:03,210
actually looked at some of the petrology

361
00:13:07,580 --> 00:13:05,670
we see signals that are very very

362
00:13:10,160 --> 00:13:07,590
indicative of what we'd expect to see in

363
00:13:12,230 --> 00:13:10,170
a back arc setting in addition to that a

364
00:13:13,550 --> 00:13:12,240
lot of these VMS type formations

365
00:13:17,350 --> 00:13:13,560
particularly with the elemental

366
00:13:20,120 --> 00:13:17,360
concentrations of zinc lead and copper

367
00:13:21,400 --> 00:13:20,130
this VMS has like the the chemical

368
00:13:25,370 --> 00:13:21,410
footprint that we like to consider

369
00:13:31,370 --> 00:13:25,380
typical for a back arc setting I didn't

370
00:13:32,570 --> 00:13:31,380
recall was the second bit right so

371
00:13:35,090 --> 00:13:32,580
acidic solutions are going to be a

372
00:13:36,740 --> 00:13:35,100
byproduct of flowing actual the solution

373
00:13:40,490 --> 00:13:36,750
through the rock you're going to pick up

374
00:13:41,780 --> 00:13:40,500
a lot of either HCl or it's a couple

375
00:13:43,370 --> 00:13:41,790
different acids you're going to get from

376
00:13:44,890 --> 00:13:43,380
actually interacting with the water so

377
00:13:46,790 --> 00:13:44,900
you're starting with normal seawater

378
00:13:48,710 --> 00:13:46,800
turkey and is probably at least a log

379
00:13:50,300 --> 00:13:48,720
unit more acidic but it's actually just

380
00:13:51,950 --> 00:13:50,310
reactions with that surrounding ground

381
00:13:59,300 --> 00:13:51,960
through that rock that's actually

382
00:14:03,200 --> 00:13:59,310
generating an acidic solution so people

383
00:14:06,110 --> 00:14:03,210
typically interpret the isotope record

384
00:14:08,780 --> 00:14:06,120
from the archaean as there is

385
00:14:11,360 --> 00:14:08,790
insufficient marine sulfate for there to

386
00:14:12,980 --> 00:14:11,370
be ice topic fractionation by microbes

387
00:14:15,590 --> 00:14:12,990
but you're saying the concentrations

388
00:14:17,450 --> 00:14:15,600
were sufficient for that fractionation

389
00:14:18,890 --> 00:14:17,460
despite the fact the ice topic evidence

390
00:14:20,180 --> 00:14:18,900
doesn't support that sure you've heard

391
00:14:21,500 --> 00:14:20,190
this question before I'm just wondering

392
00:14:24,080 --> 00:14:21,510
how you reconcile that with your

393
00:14:27,770 --> 00:14:24,090
findings well so the big question is

394
00:14:30,500 --> 00:14:27,780
what do we what isotope record are we

395
00:14:32,420 --> 00:14:30,510
looking at so the bigger the bigger

396
00:14:35,240 --> 00:14:32,430
question we're looking at life is we're

397
00:14:37,130 --> 00:14:35,250
looking at the 34 sulfur fractionation

398
00:14:39,170 --> 00:14:37,140
and then is something that actually is

399
00:14:40,820 --> 00:14:39,180
interesting so if we actually look at

400
00:14:43,460 --> 00:14:40,830
these VMS systems or any of these

401
00:14:45,500 --> 00:14:43,470
systems if we're looking enough to

402
00:14:48,020 --> 00:14:45,510
actually have sulfate preserved as well

403
00:14:49,070 --> 00:14:48,030
as sulfide there is some fractionation

404
00:14:50,660 --> 00:14:49,080
between them so in the modern

405
00:14:54,050 --> 00:14:50,670
environment the fractionation between

406
00:14:55,350 --> 00:14:54,060
sulfate and sulfide is usually around 20

407
00:14:59,040 --> 00:14:55,360
per mil in a

408
00:15:00,720 --> 00:14:59,050
EMS system maybe 30 per mil in this case

409
00:15:03,480 --> 00:15:00,730
as we start moving towards the archaean

410
00:15:06,780 --> 00:15:03,490
you are correct it starts narrowing down

411
00:15:08,250 --> 00:15:06,790
and there is a lot of work that we're

412
00:15:10,889 --> 00:15:08,260
doing as to what is the component of

413
00:15:12,389 --> 00:15:10,899
that or what is the source of that it

414
00:15:14,940 --> 00:15:12,399
could be mixing you could have a larger

415
00:15:17,670 --> 00:15:14,950
component of actual just igneous

416
00:15:19,410 --> 00:15:17,680
sulfides leaching from rock there's a

417
00:15:21,840 --> 00:15:19,420
couple different things they could

418
00:15:23,100 --> 00:15:21,850
actually be helping form that people

419
00:15:24,720 --> 00:15:23,110
have done things like if you increase

420
00:15:27,720 --> 00:15:24,730
reaction rates you can also drive them

421
00:15:31,949 --> 00:15:27,730
together I'll admit that the sulfur

422
00:15:33,600 --> 00:15:31,959
isotope record is not my absolute area

423
00:15:35,759 --> 00:15:33,610
of expertise it's mine's more just the

424
00:15:37,290 --> 00:15:35,769
bulb chemistry but I can say that you're

425
00:15:38,910 --> 00:15:37,300
really really interested in the guy

426
00:15:40,800 --> 00:15:38,920
right behind you is doing a poster doing

427
00:15:44,009 --> 00:15:40,810
exactly what you're interested in in the

428
00:15:46,740 --> 00:15:44,019
archaean sulfur record all right