Hastings Natural History Reservation

13 Jun, 10 AM - 30 Jun, 01 AM

PURPOSE OF RESEARCH PROJECT Understanding the origin of continents is a fundamental issue in geology. The average continental crust is intermediate in composition. Cordilleran-type batholiths represent aerially tremendous tracts of petrogenetically young sialic basement extending along the entire western margin of the Americas. Cordilleran-type batholiths also represent the best Phanerozoic analogues to the average upper-crustal composition of continental masses. Therefore it has been proposed that continental convergent margins represent the main sites of crustal differentiation and growth. Observations of magmatism in continental arcs and batholiths and derivative petrogenetic models come principally from upper- to mid-crustal levels exposed at the Earth's surface. These observations are complemented by experimental studies of the plausible sources and liquid line of descent of arc magmas. Many of the first order questions regarding the origin of large granitic batholiths and their relevance to crustal growth have not been uniquely answered by these constraints, in particular, the relative importance of contributions from the mantle wedge underlying arcs, pre-existing continental crust, or the subducting oceanic crust. This uncertainty leaves unresolved the extent to which the continental crust is internally differentiated or largely extracted from the mantle during arc magmatism. Whether continents grow at convergent sites, and by what mechanism and with what rates, remain open questions. Major batholithic belts of North and South America have been studied in great detail. What commonly escapes observation and prevents us from unique interpretations are the deeper crustal counterparts of the well-studied shallow batholithic exposures. Rare exposures of deeper crustal levels in arc terranes provide important insights into the nature of the lower crust of the North-American Cordillera and a testing ground for most hypotheses on the rates and mechanisms of continental growth in arcs. The current study focuses on one such exposure- the Salinian Arc of West-Central California. The project aims at: ???Quantifying the chemical and isotopic composition of mantle-derived mafic rocks emplaced in the mid-crustal section of the arc; ???Determining the chemical and isotopic composition of peridotites that occur as isolated bodies within the mid-crustal section and that represent direct samples of the subarc mantle; ???Resolving crustal vs. sub-crustal, and lithospheric vs. asthenospheric reservoirs involved in continental arc magmatism; ???Providing new constraints for the mechanisms of generation of large batholiths. 5)Understanding the origin and pressure-temperature history of the Schist of the Sierra de Salinas LOCATION OF FIELD AREAS The field area is a scattered collection of localities in the Santa Lucia and Sierra de Salinas Ranges. Most of these localities are located outside of the Hastings Reserve. ANIMAL AND PLANT POPULATIONS THAT MAY BE AFFECTED BY THE PROPOSED CLASS There are no expected affects on animal or plant populations as a result of this study. ANY POTENTIAL DISTURBANCES TO THE RESERVE'S ECOSYSTEM OR CULTURAL RESOURCES None expected. HOUSING OR OTHER RESOURCES NEEDED Housing for 1 is requested. No other special resources are requested.

Visit #7241 @Hastings Natural History Reservation

Approved

Under Project # 1787 | Research

University of Arizona - Geosciences

graduate_student - California Institute of Technology

Reservation Members(s)

Steven Kidder Jun 13 - 30, 2005 (18 days)
Steven Kidder Jun 13 - 30, 2005 (18 days)

Reserve Resources(s) | Create Invoice

Bunk House Cottage 2 Jun 13 - 30, 2005