The 40K, 238,235U and 232Th composition of the Variscan crust is derived from in-situ radiological characterization using a portable gamma-ray spectrometer [1]. Details about the analytical procedure and statistical processing of spectrometric data is given in [2]. A total of 400 measurements were performed in Sardinia, because of excellent exposure and detailed geologic information on the architecture of the Corsica-Sardinia Batholith and its country rocks [3]. The results of gamma-ray spectrometry measurements indicate that most granitoids have potential heat production rate between 0.49 and 6.92 $W m-3. Both migmatites and lowgrade metasediments are characterized by lower values in the range 1.3 – 3.1 $W m-3. The U-Th-K abundances in the Sardinian Variscan crust are 1283+340 -463 Bq kg-1, 47+18 -29 Bq kg-1 and 67+21 -31 Bq kg-1 respectively for 40K, 238U and 232Th. These values are slightly higher than those typical for the upper continental crust [4]. However, the average heat production rate of the Variscan crust of northern Sardinia is about half of that inferred in the Bohemian Massif [5]. Therefore, we argue that selective enrichment of heatproducing elements in the crust cannot account for early Permian HT metamorphism in this part of the Variscan chain.
Radiogenic heat potential of the Sardinian Variscan crust.
MANTOVANI, Fabio;
2013
Abstract
The 40K, 238,235U and 232Th composition of the Variscan crust is derived from in-situ radiological characterization using a portable gamma-ray spectrometer [1]. Details about the analytical procedure and statistical processing of spectrometric data is given in [2]. A total of 400 measurements were performed in Sardinia, because of excellent exposure and detailed geologic information on the architecture of the Corsica-Sardinia Batholith and its country rocks [3]. The results of gamma-ray spectrometry measurements indicate that most granitoids have potential heat production rate between 0.49 and 6.92 $W m-3. Both migmatites and lowgrade metasediments are characterized by lower values in the range 1.3 – 3.1 $W m-3. The U-Th-K abundances in the Sardinian Variscan crust are 1283+340 -463 Bq kg-1, 47+18 -29 Bq kg-1 and 67+21 -31 Bq kg-1 respectively for 40K, 238U and 232Th. These values are slightly higher than those typical for the upper continental crust [4]. However, the average heat production rate of the Variscan crust of northern Sardinia is about half of that inferred in the Bohemian Massif [5]. Therefore, we argue that selective enrichment of heatproducing elements in the crust cannot account for early Permian HT metamorphism in this part of the Variscan chain.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
