what on earth happened 2.7 billion years ago?

47 Pages·2008·2.99 MB·English

by  Susan Delap

WHAT ON EARTH
HAPPENED 2.7 BILLION
YEARS AGO?
Kent C. Condie
Dept. Earth and Environmental Science
New Mexico Tech
Socorro, NM 87801 USA
EXOGENIC
Atmosphere
< 103 y
Ocean
Biosphere
ENDOGENIC
107-108 y
PLANETARY CATASTROPHIES
2.7 Ga
Arc Systems
Large Igneous Provinces (LIPS)
Accretionary Orogens
3.0 2.5 2.0 1.5 1.0 0.5 0
AGE (Ga)
TECTONIC SETTINGS IN TIME
2.7 Ga
1.9 Ga
3.0 2.5 2.0 1.5 1.0 0.5 0
AGE (Ga)
JUVENILE CONTINENTAL CRUST AGE
DISTRIBUTION
2.7 Ga Zimbabwe
2.5 Ga Southern
India
TTGs
4.0 Ga
Yellowknife
Canada
DEFORMED GRANITOID ZIRCON AGES
WITH E (cid:1) +1
ND
DEFORMED GRANITOID ZIRCON AGES
WITH E (cid:1) +1
ND
CATASTROPHIC
MANTLE PLUME EVENT

c = e - r
c = crustal preservation rate
e = crustal extraction rate
r = crustal recycling rate
s = sediment subduction
b = subduction erosion
d = lithosphere delamination
r = s + b + d