A sheeted plutonic complex exposed within a tilted mid-crustal section in the eastern Transverse Ranges of California, including Joshua Tree National Park (JTNP), will be examined in detail. The section provides a wonderful opportunity for analysis of (1) the depth dependent physical changes in, and growth of, a magma plumbing system; (2) the relative importance of source region heterogeneity, contamination, and in situ crystal-liquid fractionation in forming compositional diversity in plutonic systems, and (3) the role of mid-crustal detachments and/or vertical deformation partitioning in forming orogen-scale sheeted plutonic complexes. Field mapping and detailed structural analyses combined with geochronology and geochemistry of intrusive units will allow testing of a series of hypotheses. One goal is to determine whether upper and lower crustal plutons and the underlying sheeted complex formed synchronously and thus reflect an abrupt depth-dependent change in petrogenesis and intrusive style during continental margin arc construction. They will also test the hypotheses that the complex represents both a zone of magma transfer, with the creation of vertical pathways, and a site for hybridization that formed magmas parental to upper crustal plutons and explosive volcanic rocks.
The goal is to expand our understanding of orogenesis along plate boundaries in the middle and deeper parts of continental crust. This study will dramatically affect our knowledge of vertical changes in the physical and chemical processes operating in magmatic plumbing systems that feed volcanoes. The research will be concentrated within the boundaries of JTNP and will have important positive impact on public education through geoscience outreach and interpretive activities. Over the last five years, the PIs have developed collaborations with Park Service staff at JTNP and with its interpretive arm, the Desert Institute. They will work with the Park and the U.S. Geological Survey to complete a geologic map and improve understanding of the Park?s geology, with a focus on major events in the volcanic and structural evolution that influenced formation of the Park?s landscape. Further outreach will extend that commitment through development of field trips and lectures, and will translate the results to assist park staff in enhancing public educational and curriculum materials. At USC and IUPUI graduate and undergraduate education in the geosciences will be strengthened through exceptional field, classroom and laboratory experiences, including excellent opportunities for underrepresented student groups.
