Thermal State of the Lithosphere of Patagonia Via Data of the Xenoliths

Abstract

Ultramafic xenoliths and minerals present in intrusive rocks make it possible to infer the temperature and pressure of the upper mantle and lower crust, since they preserve their physical and chemical characteristics while being transported by magmatic processes. Thermal models incorporating thermo-barometric data have been developed to estimate the thermal field. Thus, the objective of this work is to use mineralogical temperature and pressure equilibrium information to estimate lithospheric thermal field in the Patagonian region bounded by latitudes 40º - 52º S and longitudes 67º - 71º W, these coordinates correspond to the Argentine provinces of Río Negro, Chubut and Santa Cruz. Experimental mineral temperature data indicate ranges of 917-1029 ºC in the Chubut province, 877-1253 ºC in the Río Negro region and 728-1196 ºC in the Santa Cruz province. The average heat flux and temperature values at the Moho depth are 40 mWm-2 and 734 ºC, respectively. Río Negro province has the highest temperature (760 ± 45 ºC) and the lowest thermal thickness value (75 ± 11 km), while Santa Cruz province has the highest heat flux (44 ± 7 mWm-2) at Moho depth, which indicates that there are possibly two plumes responsible for the deposition of xenoliths in the region: one in Río Negro province and the other in Santa Cruz.