[X] My Assistant

[alan]

At least three massive asteroids smashed into the Earth more than 3.2 billion years ago, and caused such destruction, they dramatically changed the structure and composition of the Earth's surface. This is according to new research from scientists at the Australian National University. The team uncovered evidence of major earthquakes, faulting, and volcanic eruptions that were so violent they dramatically changed the way the Earth's surface was forming. This happened during a period that the Moon also suffered heavy bombardment.

“Our findings are further evidence that the seismic aftershocks of these massive impacts resulted in the abrupt termination of an over 300 million years-long evolutionary stage dominated by basaltic volcanic activity and protracted accretion of granitic plutons,” Dr Glikson said.

“The precise coincidence of the faulting and igneous activity with the impact deposits, coupled with the sharp break between basaltic crust and continental formations, throws a new light on the role of asteroid impacts in terrestrial evolution,” Dr Glikson said.

http://www.universetoday.com/am/publish/ea...ids.html?582005

Could one of the geologist interpret this please.

[blobrana]

Could one of the geologist interpret this please.

"The Pilbara Craton

in Western Australia has a domainal architecture, which has been interpreted to reflect a history of accretion. The Tabba Tabba Shear Zone is the major division between the East and West Pilbara blocks: this is based on significant differences in the tectono-thermal histories of the bordering terranes.

New laser ablation U-Pb zircon geochronological data, coupled with trace element data for the same core parts of the sampled mineral grains indicate a range of magmatic crystallization ages for representative igneous rocks emplaced before, during or after shearing.

The Tabba Tabba Shear Zone currently forms the eastern bounding fault of the Mallina Basin. The last major activity in the structure occurred during a major phase of oblique sinistral movement, corresponding to closure of the Mallina Basin. Ages of late syn-kinematic granitic intrusions indicate that this occurred at about 2940 Ma.

These unique locations have kept the formations from experiencing the depths that metamorphose rocks, obscuring their original sedimentary and volcanic features. "

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