AS the rocks which form the continental masses are disintegrated by the action of weathering and other geological agents, their detritus accumulates to form sedimentary rocks, ultimately on the ...

sedimentary or even an older metamorphic rock. Rocks turn metamorphic when they are subjected to very high heat and pressure. This alters the chemical and structural makeup of the minerals within ...

San Diego report that their analysis of Precambrian sedimentary rocks as old as 3.8 billion years reveal a "profound change" in the chemical reactions involving sulfur and oxygen in the atmosphere ...

Back-scattered electron images of all the thin sections of pelitic rocks and chemical compositions of minerals were obtained with an electron probe microanalyzer (JEOL-JXA-8800) at The University ...

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San Diego report that their analysis of Precambrian sedimentary rocks as old as 3.8 billion years reveal a "profound change" in the chemical reactions involving sulfur and oxygen in the atmosphere ...