GEOCHEMICAL ANALYSIS OF LATE CRETACEOUS INTRUSIVE ROCKS IN THE WESTERN MOJAVE DESERT, CA

It is unknown how high-flux magmatic events are created. The Mojave Desert is a location of interest because it contains evidence for high-flux magmatic events followed immediately by replacement of the lower lithosphere by subduction channel schists. Late Cretaceous granitoids in the western Mojave Desert have not been extensively analyzed or mapped in detail. Further chemical analysis is needed to ascertain how these rocks are related to the massive zoned intrusive suites along the Sierra Nevada crest that may be the remnants of ancient supervolcanoes. Using fourteen rock samples from across the Mojave Desert, geochemical data was collected using a XRF machine to create Harker diagrams, a simple normative calculation, and a QAP ternary diagram. The samples ranged from monzogranite, granodiorite, quartz monzonite, and quartz monzodiorite and had 63 to 71% of SiO₂ and 6 to 9% alkalis. Analysis of the Harker diagrams suggest that minerals such as plagioclase, pyroxene and/or hornblende, and either iron/titanium oxide minerals could have crystallized out of the molten material, causing chemical differentiation of the magmas. Younger intrusions appear to be more chemically differentiated on average. The analyses of these samples are fairly similar to those in the Whitney Intrusive Suite found north of the Mojave Desert, tentatively suggesting these similarly-aged granitoids may be part of a related system. The geochemical connection between the two areas suggests that further research in this area may lead to better insights into the geological history of the region and the triggers of high flux magmatism in general.