Heat production in an Archean crustal profile and implications for heat flow and mobilization of heat-producing elements

Twenty new heat flow measurements in southern Mexico are presented. These measurements document a very broad zone of low heat flow between the coastline and the Trans-Mexico volcanic belt. At the Trans-Mexico volcanic belt, heat flow increases to high values and remains high into central Mexico. Heat flow values in the Trans-Mexico volcanic belt and northward are in excess of 80 mW m−2 (1.9 μcal/cm2 s) and typical of values observed in the high heat flow regions of the western United States. The average heat flow in the Sierra Madre del Sur is 26 mW m−2 (0.6 μcal/cm2 s), in the Sierra Madre Oriental is 89 mW m−2 (2.1 μcal/cm2 s), and in the Trans-Mexico volcanic belt is 91 mW m−2 (2.2 μcal/cm2 s). A surface heat flow profile was constructed perpendicular to the trench, and the data were matched with a simple thermal subduction model. The resulting final model parameter set suggests that the angle of subduction is low and that convective heat transfer in the back arc region is probable. For data south of the Trans-Mexico volcanic belt, reduced heat flow values (upper crustal radioactive effect removed) are less than 15 mW m−2 (0.4 μcal/cm2 s). Thus essentially the total mantle heat flow is being absorbed by the subducting block. The values are lower than the heat flow observed in the Sierra Nevada Mountains of California and support the hypothesis that the heat flow couple associated with the Sierra Nevada Basin and Range province is a relic subduction zone thermal pattern.

Heat flow in southern Mexico and the thermal effects of subduction

The Pikwitonei and Sachigo subprovinces of central Manitoba provide a cross-sectional view of the Superior Province crust. In cross section, the upper to mid-level crust is composed of synformal gr...

Heat production and thermal conductivity of rocks from the Pikwitonei–Sachigo continental cross section, central Manitoba: implications for the thermal structure of Archean crust

Retrospective trend analysis of the content of U.K. air particulate material 1957–1974

Capacitance-voltage characteristics have been obtained for Schottky barrier diodes, formed on polished surfaces of natural p-type semiconducting diamond, before and after illumination with radiation capable of neutralizing ionized donors in the depletion layer. Plots of 1/C2 versus V for the two cases have yielded values for both the acceptor concentration NA and the donor concentration ND. Comparison of these data with those obtained from Hall effect measurements indicate that the latter overestimate the value of NA-ND by almost a factor of 2. The boron concentration has been determined in approximately the same surface layer as the capacitance measurements by detecting the alpha -particles emitted during irradiation with 700 keV protons using the reaction 11B(p, alpha 1)8Be* to 2 alpha 2. A quantitative correlation has been obtained between the boron and acceptor concentrations.

http://iopscience.iop.org/article/10.1088/0022-3727/9/6/008/pdf

Determination of boron in natural semiconducting diamond by prompt particle nuclear microanalysis and Schottky barrier differential-capacitance measurements

L. Salmon

Papers

Analysis of gamma-ray scintillation spectra by the method of least squares