Hi Blue Swims, Thought id weigh in again with my 2c on the...

Hi Blue Swims, Thought id weigh in again with my 2c on the anomaly topic

I’ll justpost this quote from Wikipedia:

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“Cerium isa rare-earth element (lanthanide) characterized by two different redox states:III and IV. Contrary to other lanthanide elements, which are only trivalent(with the notable exception of Eu2+), Ce3+ can be oxidized by atmosphericoxygen (O2) to Ce4+ under alkaline conditions.[2]

The ceriumanomaly relates to the decrease in solubility, which accompanies the oxidationof Ce(III) to Ce(IV). Under reducing conditions, Ce3+ is relatively soluble,while under oxidizing conditions CeO2 precipitates.[1] Sediments depositedunder oxic or anoxic conditions can preserve on the long term the geochemicalsignature of Ce3+ or Ce4+ upon reserve that no early diagenetic transformationaltered it.[1]”

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So to myunderstanding, its not the mobility of Ce that creates the anomaly, it’s the LACK ofmobility under certain conditions. When oxygen gets to the ionic cerium (+3) itturns it into Cerium Oxide. Now the Cerium has moved to a +4 state, but what’simportant is that this oxide forms easily and it is INSOLUBLE. Other ionic REEsstay ionic (+3) and so stay SOLUBLE and can therefore move with water.

So ifoxygen gets to the deposit, Ce oxidizes and stays put while the rest get washedfurther DOWN into the clays. This is called a secondary enrichment process, andresults in a positive anomaly on top, with a negative below. It is a goodindication that the rest of the REE’s are still ionic, as they are moving DOWNwith permeating water. The positive anomaly on top can also be physicallyeroded away, leaving just a negative. All OK.

Thissecondary enrichment is an important process in the wet somewhat ruggedenvironments of other Chinese style IA clay deposits. It allows RE’s to continuously filterdown through the clays and concentrate there before the upper layers getremoved through erosion.

Here’s theimportant bit for Jupiter though, the inverse is not necessarily true. Lack of ananomaly doesn’t necessarily mean lack of ionic nature. It might, but it certainly doesn’thave to. I’ll alter the last Wikipedia sentence:

“Sedimentsdeposited under anoxic conditions can preserve on the long term the geochemicalsignature of Ce3+”

If the Cestays +3 it will behave as the rest of them do, and move with water in the sameproportion as the rest of them. So if Jupiter was formed, and has relativelystayed, under anoxic (oxygen poor) conditions (and plenty of flat sedimentaryenvironments are anoxic), not much of a Ce anomaly, either positive ofnegative, will develop.

So Jupiter,on the sparse data I have seen so far, sits as bit of an enigma for me. It has the REenrichment, grades are plenty high enough, yet that enrichment doesn’t seem tohave come from that particular secondary process I mentioned above. That secondary processis a function of the wet, vegetated, rugged environment (read oxic). YetJupiter is in a flat, dry, sparsely vegetated environ, (read anoxic?), and hasbeen for a long time. Some other variations on weathering processes are at play here.

Anyway,thought id clarify my understanding of the Ce anomaly again, as your right it is tricky, and knowledge of IA clays deposits outside China is in its infancy.