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[Music]

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[Applause]

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thank you for the introduction and I'm

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very sorry for this such a table boys so

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I hope you can understand my babe you

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have not my not my talk itself okay I'm

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Cosima Gucci from top in the city in

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Japan and I'm talking about the result

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of the geochemical analysis of the

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samples from Ghana okay why do we are we

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interested in 2.2 GA a period of 2.2

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billion years ago

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well this figure is from anions at all

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2014 which has been frequently used in

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this kind of talk and then until point

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to g8 here Saudi to point to GA is just

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before the just after the right after

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the infant lies of oxygen in the

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atmosphere

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goe great oxidation event at around 2.4

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to 2.2 GA and by the time atmosphere

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could have been oxygenated ensure ocean

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- but how about the deep ocean so so far

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a few studies of non sterile environment

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which is deep deep employment at the

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point GA has been done so please

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remember that a monthly super group in

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Austria and the transport super group in

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South Africa and also Huron Ian super

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group in Canada or all of these Imperial

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important jurist record have mainly

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shower rocks in the upper portion okay

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so here is the step wise in model of the

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step by rock sedation of the Artemis the

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ocean system this is originally from a

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casting to 1993 and then 1997 so the

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front step stage 1 to stage 4 the time

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is from left to right we have no oxygen

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in the atmosphere no in this erosion one

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no in no no action in the deep ocean but

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with time we at most oxygen is invading

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indeed port so we have may we may we may

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have had a goe for the transition from

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stage 2 to stage stage 3 okay

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the timing insisted controversial but my

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interest is here how long did it take

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for the deep ocean to be fully ocean

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aided quite soon or we have a time lag

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but this is just the motivation of both

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of my lab study ok so I looked for the I

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dropped a tear geologic map and to look

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for deep samples throughout the world

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and then I found that theater is a

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greenstone belt in Ghana

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if whose age is about 2.2 GA and then

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about 10 years ago I first went to Ghana

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to do a preliminary work then I decided

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that I realized that this is a very good

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place perfect place to do drink to

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obtain a deep faces samples from 2.2 G

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period and then luckily enough I could

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obtain funding to do to realize the

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continent

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drink in Ghana and that was that

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happened in fall 2015

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in the in this area sauce fish sauce

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with Ghana and then we obtained 160

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meter wrong 2.2 GA deep faces

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sedimentary rocks

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these are least altered and then we got

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a 100% recovery so this is based on

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alternation of shales and volcanic

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stones and sand stones some kosa grains

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and for this study samples are from the

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uppermost 20 meter unit so if we assume

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the we denote segmentation rate but we

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assume 5 millimeter per thousand year

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then this 20 meter section represent a

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for me only 4 million year period ok ok

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this is a volcanic sandstone cosa grains

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and greenish volcanic suta stones and

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then black shales

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but this presentation is only for this

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the up the uppermost section and here's

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the photo of the actual core and which

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will be

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expanded in next ride so here is the

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just representative photo of the doing

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activity in Ghana there were lots of

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there were lots of lots of dust coming

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from sovereign desert and also mist from

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the nearby ocean and then kids during

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activity was always observed by tens of

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kids attentions of curious kids okay so

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anyway I could obtain this kind of

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really beautiful durable samples okay so

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first I would like to show you the

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result of the ion speciation analysis

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here are the profiles of a young

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speciation from left to right onion pie

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right pirate bond onion and iron

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carbonate onion magnetite magnetite bond

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iron and iron oxide and then total iron

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Fe T was Sigma T what Ryan and on this

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in this dips profile LED dashed line

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represents the average the iron content

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elaborate shell over pas by from Tara &

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McLennan 1985 textbook then I like to I

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would like you to look at if Dan's right

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I am pirate pirate aliens

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we divided the samples into three units

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pirate pour over samples here and pilot

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for a Poisson process here in open

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symbols and then pirate rich samples

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with fuel chuckles okay then then I drag

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to show you the this kind of a a

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speciation plot the y axis is a onion

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pirate onion / a highly active onion and

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the holy x-axis oesn't axis this is ion

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highly reactive to iron Toto Toto Ryan

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so obviously many of the samples with

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no pirate pirate pro samples are plotted

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in this object domain here and then

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pirate each samples profit in this new

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clinic region this feature is also

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evident in this sulfur carbon prot

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sulphur pirate bond sulfur and Owen

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carbon content open symbols pirate press

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improves up rotate on the trend of

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normal marine this is a representative

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slope for the phanerozoic a typical

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known surf Enoch black shales normal

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shells I should say and then reads

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pirate beach samples also Proteus in

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this region suggesting nukes any

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conditions or seen genetic pirate

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formations in the water crime okay so

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the environment was essentially oxic but

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with sporadic development of anoxic or

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York City conditions with time then I

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would like to show you the new element

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concentrations for samples the

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concentrations are normalized by a pas

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post alkane australian average sale okay

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again Brock Ryan's present pirate which

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samples upper samples and Gen Z's blue

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and orange rinds pilot Pro samples okay

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and we we seems to have some positive

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same anomaly right they exist but no

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European man normally right this is

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based normalized to a pas right so

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basaltic

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segmental rocks should have slightly

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higher elevated European concentration

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on this kind of rot so this is not the

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European anomaly right so pyrite Pro

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samples have more rustic basalt rock

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signature right flat pattern with some

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depleted in right where sediment

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concentrations right and then while

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pyrite reached samples here so modern

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seawater reich lightest element is

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smaller than heavier

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rare earth elements a signature with

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more educated total health content okay

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so actually this is quite consistent

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with the Yuke's knee conditions for

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pilot formation impaired examples this

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kind of rare earth element pattern is

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quite common for the anoxic water

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crammed in modern-day environment this

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is due to a reductive dissolution of

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release of a serum from sediment to the

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opening water crown okay

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the new experimental cinema normally

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then I operated this ratio City mobile

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serum stove values so this is just you

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know sodium concentration divided by c/d

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monster bad news is it's a hypothetical

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value between lance demand Presidium

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here

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right then in the robot sections we have

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limited very limited range for the same

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same stuff are used but for pirate poor

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upper part we have slight increase in

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the range and Beaufort the pirate each

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samples only due to date and points or

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spectacular but we have a increase in

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range of this area mobile City monster

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like ratios okay again parentage samples

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have wider range of same over cm star

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ratios and this may represent the

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changes in the dock state with time

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right sporadic

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development of York's in equinoxes water

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cram and to form pyrite and two more to

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have more increased concentration of a

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cerium interval in the water from okay

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then I would like you to look at the

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trace metal concentrations for these

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samples okay and then

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x-axis for these four plots or terrible

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amoxil it should be it weight percent

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and versus four kinds of transition

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narrows chromium molybdenum nickel and

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copper and only parity samples here

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filled circle have right

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positive correlations with aluminum

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oxide content our T value is 0.6 five

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seven zero two zero and five and fifty

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five this is quite small so this may

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suggest that we may have had increased

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content of measuring first I thought

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that these metals could have been

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provided to the sedimentary environment

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by hydro solar input but this net metals

217
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have more weaker correlation with iron

218
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content so I then thought that these are

219
00:11:54,050 --> 00:11:50,070
due to enhanced continental measuring or

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changing simply mythology more Coco sir

221
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grains okay then I would like to I'd

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like you to look at a lower peridot

223
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samples here okay so para trás samples

224
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in the roba sections have V correlation

225
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between organic carbon content and iron

226
00:12:12,850 --> 00:12:11,550
comrade content that is shown in the

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next slide

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okay well so pilot resorts in the rural

229
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sections have this kind of correlations

230
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suggesting that Pharaoh Sonia informed

231
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by a biological physical reduction

232
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combined with but bicarbonate ion to

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form iron carbonate eventually and

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Pyrrha didn't form effectively because

235
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the biogenic sulfide was not available

236
00:12:42,710 --> 00:12:40,200
in this toxic environment so iron

237
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two-plus combined with bicarbonate not

238
00:12:52,250 --> 00:12:50,130
with sulfide okay then this kind of this

239
00:12:54,199 --> 00:12:52,260
is just a don type of us right so I

240
00:12:57,110 --> 00:12:54,209
measure the converse of composition but

241
00:13:00,650 --> 00:12:57,120
Owen carbon and they are mostly around

242
00:13:03,650 --> 00:13:00,660
-25 formula which is not so special okay

243
00:13:07,580 --> 00:13:03,660
so this is just

244
00:13:11,570 --> 00:13:07,590
showing the origin of when carbon in the

245
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samples which may be photosynthetic

246
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activity in the upper oceans so

247
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conclusions geochemical and I stopped

248
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analysis of 2.2 Gao samples in Ghana

249
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suggests of the drawings essentially oxy

250
00:13:34,400 --> 00:13:32,220
deep ocean and coma carbon is provided

251
00:13:36,380 --> 00:13:34,410
to deep ocean from the soft ocean and

252
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then iron reduction could have occurred

253
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and then spot the development of anoxic

254
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luke scenic water crown right leading to

255
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us in genetic malformations so this is a

256
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major conclusion it didn't take long for

257
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the deep ocean to the commode sick right

258
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after the infra goe at around 2.4 to 2.2

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GA and this study has implications for

260
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the redox evolution of the atmosphere

261
00:14:04,640 --> 00:14:01,640
ocean system in the early Earth and

262
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future work would be to measure surface

263
00:14:10,010 --> 00:14:07,980
of competitions and Ayana stops but for

264
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multiple Nam and chromium isotopes I

265
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would like to have your help need

266
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collaborations the samples the samples

267
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can be shared upon request

268
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ok so thank you for your attention maybe

269
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one quick question while we're

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transferring speakers in please the last

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speaker come to the front okay thank you