THERMAL REGIME OF THE SOUTHERN BASIN AND RANGE PROVINCE .1. HEAT-FLOWDATA FROM ARIZONA AND THE MOJAVE DESERT OF CALIFORNIA AND NEVADA

With about 150 new heat flow values, more than 200 values of heat flow are now available from the crystalline terranes of southern Californi a, the Basin and Range Province of Arizona, and Paleozoic sedimentary rocks of the southwestern Colorado Plateau (CP). Heat flow ranges from about 5 mW m(-2) on the CP near Flagstaff, Arizona, to more than 150 mW m(-2) in the crystalline rocks bordering the Salton Trough in SE Ca lifornia. The heat flow pattern within this region is complex, althoug h it correlates with regional physiographic and tectonic features. Unl ike the adjacent Sierra Nevada Batholith where heat flow is a linear f unction of near-surface radiogenic heat production, no statistically s ignificant correlation exists between heat flow and heat production in the study area, possibly because of its complex tectonic history, inv olving lateral movement of basement terranes, and relatively young hea t sources and sinks of different strengths, ages, and durations. Conte mporary and Neogene extensional tectonism appears to be responsible fo r the very high heat flow (>100 mW m(-2)) associated with the Salton T rough and its neighboring ranges, the Death Valley m fault zone and it s southward extension along the eastern boundary of the Mojave block, and zones of shallow depth (<10 km) to the Curie isotherm (as inferred from aeromagnetic data) in west central Arizona. Low (<60 mW m(-2)) h eat flow in the Peninsular Ranges and eastern Transverse Ranges of Cal ifornia may be caused by downward advection associated with subduction and compressional tectonics. Relatively low heat flow (67 +/- 4 mW m( -2)) is also associated with the main trend of metamorphic core comple xes in Arizona, and the outcropping rocks in the core complexes have a low radioactive heat production (1.3 +/- 0.3 mu W m(-3)). compared to the other crystalline rocks in the region (2.1 +/- 0.2 mu W m(-3).