Autori: Brady, R.J., Ducea, M.N., Kidder S. and J. Saleeby

Editorial: Lithos, 86, p.229-244, 2006.

Rezumat:

Geochemical analyses and geobarometric determinations have been combined to create a depth vs. radiogenic heat production database for the Jurassic-Cretaceous Sierra Nevada batholith, California. This database shows a wide range of heat production values at any given depth, but an overall pattern of relatively invariant heat production of ~2 ?W/m3 within the ~3-km-thick volcanic pile at the top of the batholith, below which heat production increases to an average value of ~3.5 ?W/m3 at ~5.5 km, then decreases to ~0.5-1 ?W/m3 at ~15 km depth and remains at these values through the entire crust below 15 km. Below the crust, from depths of ~40-120 km, the upper mantle appears to have an average radiogenic heat production rate of ~0.14 ?W/m3, which is higher than the rates from most published xenolith studies, but reasonable given the relatively young age of the mantle lid. The pattern of radiogenic heat production suggested by the depth vs. heat production database is not consistent with the downward-decreasing exponential distribution predicted from modeling of surface heat flow data. The suggested distribution predicts a reasonable range of geothermal gradients (basal crustal temperatures are highly dependent on the poorly constrained mantle heat flux). Interestingly, it also predicts that essentially all of the present day surface heat flow from the Sierra Nevada could be generated within the crust, requiring that there is very little heat flux from the mantle, and/or the crust has been modified significantly since the Cretaceous.

Cuvinte cheie: heat production, heat flow, magmatic arcs