Questions tagged [geochemistry]

The science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems.

Filter by
Sorted by
Tagged with
7
votes
1answer
394 views

What ozone depleting chemicals can salt produce?

According to How Long Will Life Last On Earth, 250 million years ago Siberia underwent a large a prolonged period of volcanic activity. It has been speculated that large salt deposits that existed in ...
7
votes
2answers
184 views

Recreating the rock cycle

I want to recreate the rock cycle using some item that can behave as a rock. The purpose of this is to get a point across to my students about how really there is a reason why the rock cycle is called ...
12
votes
1answer
2k views

Why do most opal deposits occur in Australia?

According to the Wikipedia page about opals, this hydrated amorphous silica based gemstone is most commonly found in Australia, with according to the page, over 90% from Australia. Opal from Coober ...
8
votes
1answer
127 views

Magma resultant from group 1 and group 2 elements?

I was recently speaking with a geology professor over lunch at a university who has a theory that I've never heard before. His postulation was quite compelling and I was hoping to do a little digging ...
5
votes
0answers
65 views

Why is seawater saline? [duplicate]

Why is seawater saline and not fresh? Could it be saturated with anything else, like, say, dissolved metal?
19
votes
3answers
2k views

Why does Earth have abundant oxygen in the atmosphere?

Because of photosynthesis, obviously. But then it's not actually that obvious after all, because photosynthesis is mostly balanced by respiration. We can summarise the processes of photosynthesis ...
7
votes
1answer
130 views

Do different lavas have different volcanic volatiles associated with them?

This question was inspired by the question Predicting volcanic eruptions by experimentally proven volatile outgassing observations Depending on the type of volcano, three types of lava are released ...
9
votes
0answers
81 views

Predicting volcanic eruptions by experimentally proven volatile outgassing observations

In the abstract for the article Forecasting Etna eruptions by real-time observation of volcanic gas composition (Aiuppa et al. 2007), the authors assert that real time monitoring of volcanic volatiles,...
7
votes
1answer
905 views

What is the origin of the Laacher See caldera magma in Germany?

The Laacher See is a volcanic crater lake in Germany, with a diameter of 2 km (1.2 mi) in Rhineland-Palatinate area, approximately 24 km (15 mi) northwest of Koblenz and 37 km (23 mi) south of Bonn, ...
20
votes
0answers
392 views

How are Mauna Loa $\ce{CO2}$ monthly trends computed?

The problem I am trying to figure out how $\ce{CO2}$ concentration trends are computed in the data provided by the Earth Systems Research Laboratory Mauna Loa Observatory. The data contains monthly ...
6
votes
1answer
217 views

What is the mechanism for deep-sea volcanism of the Gakkel Ridge in the Arctic?

Related to an earlier question, What is the geochemical source for the helium detected in deep Arctic explosive eruptions?, where it is stated in the linked article that there is evidence of explosive ...
7
votes
3answers
2k views

The different types of plagioclase

The fractions of albite $\ce{NaAlSi_3O_8}$ and anorthite $\ce{CaAl_2Si_2O_8}$, which I call $\ce{Ab}$ and $\ce{An}$ in the following list, present in a plagioclase are often used to define it in the ...
7
votes
2answers
379 views

Acidity of rock

I read that the acidic character, or, better, persilicic character of a rock is determined by a content of more than $65\%\ \ce{SiO_2}$. A rock is defined, by the texts available to me, as ...
7
votes
1answer
98 views

What is the geochemical source for the helium detected in deep Arctic explosive eruptions?

Recently, there has been explosive deep-ocean volcanism detected along the slowly-spreading Gakkel Ridge in the Arctic Ocean (see map below), according the National Geographic news article Arctic ...
12
votes
3answers
404 views

Nuclear testing and the Anthropocene, a chemostratigraphic link?

The Anthropocene is described by Wikipedia as an informal geologic chronological term for the proposed epoch that began when human activities had a significant global impact on the Earth's ...
10
votes
1answer
349 views

What is the geochemical origin of carbon dioxide with the 'white smokers' of the Champagne Vent?

Associated with the NW Eifuku volcano, a small submarine volcano in Japan's Volcano Island chain in the Pacific Ocean is a carbon dioxide rich hydrothermal vents called white smokers by NOAA (see ...
10
votes
1answer
126 views

What's the partition coefficient (D) of Nb for apatite?

Was there any experimental study that determined $D$ for apatite and silicate liquid? The GERM Kd database only lists one study with carbonatite liquid, but that's not what I'm looking for.
10
votes
1answer
131 views

What does geochemical data tell us about Earth's earliest palaeoclimatic conditions?

Given that the age of the oldest zircon samples are about 4.4 billion years old, and meteorites and other extraterrestrial samples can also give us some indication about the Earth's composition into ...
20
votes
2answers
5k views

What is the origin of the ocean's salt?

We know we cannot live without salt, but an investigation into the origins of ocean's salt leads one to believe that this issue is not fully resolved yet. What geological phenomenon caused the earth ...
13
votes
1answer
29k views

What are the high field strength and large ion lithophile (HFS or HFSE & LIL or LILE) elements?

There are two groups of elements that are frequently mentioned when discussing incompatible trace elements. They are the high field strength elements (HFS or HFSE) and the large ion lithophile ...
10
votes
1answer
268 views

Why would magma have high amounts of nickel and chromium?

I am doing a research project on Mount Lamington and through my research I have found that its magma has unusually high amounts of chronium and nickel. What would cause this to happen? Is there ...
13
votes
3answers
504 views

What, if any, paleoclimate data can be derived from igneous rocks?

Paleoclimate data often derives from sedimentary rocks. Metamorphic rocks can also contribute to paleoclimate information in a wide variety of ways. What about igneous rocks? I guess that this can ...
8
votes
1answer
436 views

Release mechanism for methane clathrate at the PETM

The Paleocene-Eocene Thermal Maximum (PETM) is a well-studied warming event near the Paleocene-Eocene boundary. It is characterized by its extreme warming rate: from onset to recovery the event lasted ...
36
votes
5answers
3k views

How do we know the asteroids formed at the same time as earth?

In continuation of the question Why is Earth's age given by dating meteorites rather than its own rocks?, what evidence do we have that the asteroids indeed formed at the same time as earth? Is there ...
34
votes
3answers
14k views

Why is Earth's age given by dating meteorites rather than its own rocks?

Reading a course on Precambrian, I read that: Earth Age (around 4.5 billion years) is dated thanks to the meteorites hitting Earth during its formation rather than the inner materials composing the ...
8
votes
3answers
399 views

How do archaeologists address time dilation when analyzing carbon dating results?

It is a proven fact that the gravitational force exerted upon an object directly affects that objects experience of time; the greater the gravity, the slower time passes, and visa versa. While the ...
12
votes
2answers
157 views

Are there any metal anomalies other than iridium in the K-Pg boundary?

The iridium anomaly marks the elevated concentration of iridium in sedimentary deposits of the Cretaceous-Paleogene boundary. The iridium is said to come from the impactor, which is supposed to have ...
4
votes
1answer
286 views

What are the formula weight and gram-formula unit (gfu)?

I'm reading Shaw's "Trace Elements in Magmas" and in his page 16 he writes the following: ...It is necessary to look at the relationship between $c_i$ and $x_i$, i.e. the weight and molar ...
26
votes
4answers
12k views

What is the origin of the dominant atmospheric nitrogen content in Earth's atmosphere?

Comparing the atmospheric compositions of Earth with our nearest neighbours: As the table shows, the Earth's atmospheric nitrogen concentration is 78%, compared to 3.8% for Venus and 2.7% for Mars ...
13
votes
1answer
354 views

How much silicon is in the Earth's core, and how did it get there?

With some informal conversation with a peer of mine, he had suggested that there is evidence (which he couldn't find,but had remembered reading) that there was Silicon in the Earth's core. I referred ...
13
votes
1answer
4k views

What is it about ancient craton geology that results in associated kimberlite pipes containing economic diamond deposits?

According to the Australian Geological Survey Organisation paper Kimberlite and lamproite diamond pipes (Jaques, 1998), economic deposits of volcanically-formed diamonds are restricted to ancient ...
11
votes
1answer
151 views

What is the mechanism behind changes in oxidation state (of iron, for example) as magma rises?

From this answer, I learned that rising magma may change oxidation state, which I wasn't aware of. In [#1], the authors state in the abstract The conventional view holds that the oxidation state ...
9
votes
1answer
148 views

What makes the conditions at the core/mantle boundary ideal for aluminum to combine with other elements besides oxygen?

Recently, steinhardite was accepted as a new mineral by the International Mineralogical Association. It's quite an interesting story in its own right. There's an interesting article in New Scientist ...
9
votes
1answer
397 views

How does the composition of volcanic rock change as it makes its ascent towards the surface?

A schematic for the fluid mechanics of a volcano is represented below. Graciously borrowed from Figure 1 of the reference cited below From the caption of that figure: During explosive eruptions, ...
11
votes
3answers
1k views

Looking at ocean depth/latitude profiles of dissolved oxygen and nitrate. Why is dissolved oxygen low when nitrate is high?

I was looking at a depth profile of a segment of the Atlantic Ocean. What is the relationship between dissolved oxygen and nitrate? When nitrate is high, dissolved oxygen is low and vice versa. I've ...
11
votes
2answers
1k views

Why are alkali basalts found at rifting centres and on top of 'plumes', whereas MORBs are generally tholeiitic?

So I was essentially wondering why it was that the basalts on top of 'plumes' at 'hotspots' (sometimes called OIBs, ocean island basalts) and at continental rifting centres are enriched in alkaline ...
12
votes
1answer
74 views

Why are titanium oxides lumped in with magnetite for the purposes of analyzing water bubble nucleation?

I was reading a bit about the fluid mechanics of volcanoes to further understand some of the dynamics of "magma wagging" from my earlier question. From [2]: Heterogeneous nucleation, in ...
14
votes
1answer
142 views

Does the heating of the oceans due to greenhouse effect negate the acidification due to increased CO2 levels?

As I understand, the dissolving of carbon dioxide leads to increased acidification of the oceans, and thus increased atmospheric CO2 levels would lead to more dissolution in the oceans and thus ...
16
votes
1answer
482 views

Why won't Yellowstone explode?

From my understanding Yellowstone is a massive super-volcano, so why isn't it active? Where has its (correct me if I'm using the wrong term) hot-spot gone? Can it still erupt?
10
votes
5answers
28k views

Which theory is stronger, that iron came from outside or was formed within earth?

Where is the current body of science learning towards, that iron came from meteor or it was somehow formed on earth?
16
votes
2answers
629 views

Why is there Uranium in Earth's Crust?

Uranium's density is greater than most elements, so you would expect it to settle to the bottom of a volume of fluid. In the case of the Earth, which was molten in the beginning, you might then expect ...
12
votes
1answer
332 views

Are there significant amounts of rare earth elements on Iceland?

The rare earth elements form in magmatic rocks. The Iceland is very active vulcanic region, and it's, to my knowledge, entirely build from magmatic rocks. So it wouldn't be surprising if there were ...
12
votes
2answers
392 views

What does groundwater consist of?

I heard that groundwater is rich in minerals and fluorides, but I have no clear thoughts on what else it contains and whether the ground water differs from area to area. Can someone please shed some ...
10
votes
1answer
1k views

Why do Volcanoes give out so much Sulphur Dioxide and Carbon Dioxide?

From my understanding, the mantle is in a highly reduced state, so I can't understand why a volcano would give off a highly oxidised gas such as sulphur dioxide. Carbon dioxide is too an oxidised ...
24
votes
2answers
4k views

Natural nuclear explosions

I'm aware of the Oklo reactor and other natural nuclear fission reactors, in which geological processes can lead to the formation of a sustained, self-regulating uranium fission reactor. Is it also ...
4
votes
1answer
800 views

What are the implications of the recent discovery that huge oceans exist close to the mantle of the Earth? [duplicate]

I was of the notion that as we get deeper into the Earth, it gets hotter and hotter. If so, how can there be huge oceans (they seem bigger than our Pacific) exist at such a place? If so, what are the ...
15
votes
1answer
312 views

When a tectonic plate subducts, does any of the subducted material melt, or is it just the mantle above the subducted slab that melts?

I know that water released from oceanic crust causes melting of the mantle in subduction zones, but does any part of the subducted slab melt as well - such as the sediments on the slab or the basalt? ...
11
votes
1answer
118 views

Why would a suite of related rocks have one anomalous sample?

I have a suite of rocks that have nearly identical major element chemistry, but a single sample has quite different trace element concentrations. All the rocks are trachydacites. I know the analysis ...
11
votes
1answer
268 views

Use of Neodymium in Paleoceanography

$\varepsilon_{Nd}$ (i. e. the relative deviation of $\frac{^{143}Nd}{^{144}Nd}$ from a standard) is often used as a proxy in paleoceanography to identify the basin of origin of oceanic currents. But ...
8
votes
1answer
125 views

What is the concentration of silver in tap or freshwater in the United kingdom

Can anyone tell me the concentration of silver in uncontaminated water ways, or treated tap water in the united kingdom? sources would be desirable too