Paleo heat flow in areas of Sedimentary Exhalative (SEDEX) deposits of Eastern Brazil

Abstract

Representative values of fluid inclusion temperatures and radiogenic heat production values have been compiled as part of an attempt to determine paleo heat flow in areas sedimentary exhalative (SEDEX) deposits in thirteen localities of eastern Brazil. The results obtained indicate heat flow in excess of 80 mW/m2in areas of mineral bearing sulphide ore deposits, during periods of ore forming processes. Such anomalously high heat flow are more than twice the present-day values for stable tectonic units of Precambrian age. There are indications that high heat flow values were sustained by circulation of hydrothermal fluids in the upper crust, during periods not exceeding a few hundred million years. The resulting geothermal episodes may be considered as constituting short-period “heat pulses” occurring in stable tectonic environments, generated by magma emplacements in the upper crust, leading to formation of areas of sulfide ore deposits. Model simulations indicate that subsidence episodes induced by stretching and magma under-plating constitute the mechanisms for high heat flow during the ore-forming processes.

Heat flow variations in the Antarctic Continent

“…The next step is determination of heat flow corresponding to the emplacement temperature (Te). For a crust with temperature dependent thermal conductivity (), the relevant relation for magmatic heat flow (qe) corresponding to residual temperature (Te) as a function of depth (z) is (Carslaw and Jaeger, 1959;Iyer and Hamza, 2019):…”