Does Large-Scale Crustal Flow Shape the Eastern Margin of the Tibetan Plateau? Insights From Episodic Magmatism of Gongga-Zheduo Granitic Massif.

The mechanisms driving crustal deformation and uplift of orogenic plateaus are fundamental to continental tectonics. Large-scale crustal flow has been hypothesized to occur in eastern Tibet, but it remains controversial due to a lack of geologic evidence. Geochemical and isotopic data from Cenozoic igneous rocks in the eastern Tibet-Gongga-Zheduo intrusive massif, provide a way to test this model.

Quantifying Crustal Thickness in Continental Collisional Belts: Global Perspective and a Geologic Application.

We present compiled geochemical data of young (mostly Pliocene-present) intermediate magmatic rocks from continental collisional belts and correlations between their whole-rock Sr/Y and La/Yb ratios and modern crustal thickness. These correlations, which are similar to those obtained from subduction-related magmatic arcs, confirm that geochemistry can be used to track changes of crustal thickness changes in ancient collisional belts. Using these results, we investigate temporal variations of crustal thickness in the Qinling Orogenic Belt in mainland China.

Quantifying crustal thickness over time in magmatic arcs.

We present global and regional correlations between whole-rock values of Sr/Y and La/Yb and crustal thickness for intermediate rocks from modern subduction-related magmatic arcs formed around the Pacific. These correlations bolster earlier ideas that various geochemical parameters can be used to track changes of crustal thickness through time in ancient subduction systems. Inferred crustal thicknesses using our proposed empirical fits are consistent with independent geologic constraints for the Cenozoic evolution of the central Andes, as well as various Mesozoic magmatic arc segments currently exposed in the Coast Mountains, British Columbia, and the Sierra Nevada and Mojave-Transverse Range regions of California.