PETROLOGY AND GEOCHEMISTRY OF THE EJB DIORITE, WHITE-INYO MOUNTAINS, EASTERN CALIFORNIA
Observations of the contacts between the EJB diorite and the adjacent rocks reveal several different relationships. In at least one case, the contact relationships between the diorite and the surrounding BCG are characterized by apparent magma mingling. Elsewhere, contacts are characterized by elongated xenoliths of the diorite within the BCG suggesting intrusion into sheared ductile diorite. Finally, some contacts are characterized by angular, broken diorite xenoliths surrounded by BCG. Collectively, these observations suggest that the BCG may have intruded a cooling diorite mass of spatially variable rheology.
Preliminary XRF analyses of the EJB dioritic rocks shows them to be enriched in MgO and TiO2, and depleted in Na2O and K2O, relative to other igneous rocks of the EJB. Trace element concentrations of the diorites include the following ranges: V, Cr: 100-300 ppm; Co: 8-50 ppm; Ni: 7-90 ppm; Cu: 25-100 ppm; Zn: 80-120 ppm; Rb: 30-80 ppm; Sr: 700-2000ppm; Zr: 130-400 ppm; and Ba: 800-1800 ppm. Preliminary assessment of these data suggests that the diorite may have either mixed with the BCG to form the JFQM or fractionated to form the JFQM and the BCG.