Re: Geology of a recently terraformed planet

In article <1140234548.867834.290870@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
sigidunum@xxxxxxxxx wrote:

Consider a planet that's broadly Earthlike in size, rotation,
insolation, etc. But it's either lifeless, or has only anaerobic
bacteria. Like Earth in the deep Precambrian, it has a reducing
atmosphere.

Human colonists arrive and terraform it -- algae, then invertebrates,
fungi, land plants, and on up the food chain.

Let us say this takes a thousand years; at the end of which time the
planet has a breathable atmosphere, topsoil, and enough free-living
plants and animals for a human to survive by hunting and fishing.

Now: how will it be different? from Earth?

Very likely, few or no significant metallic-mineral deposits, either
(including uranium). Since it's likely that almost all such deposits,
here on earth, are biologically-mediated, and formed in the 10 exp4 to
10exp6 year age-range. [1]

Which is likely to put a severe crimp in the new colony's industrial
base. Not something I recall being addressed in terraforming-SF (except
peripherally (K) in Niven's _Spiral Something_.
______________________
[1] A notable exception are some Pt-group & Cr deposits, which appear to
form by gravity-segregation (fractional crystallization, really) in a
few slow-cooling ultramafic magma-chambers. A slender reed to hang an
industrial civilization on....

Cheers -- Pete Tillman
Geologist & prospector
.

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