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[1] Twelve new heat flow values determined at nine sites and heat production estimated from radioelemental measurements at 330 sites in the southern granulite province (SGP) bring out contrasting crustal and subcrustal thermal characteristics between the SGP and the adjacent Archaean Dharwar greenstone-granite-gneiss province (DP) in south India. A twolayer granulitic crust of Late Archaean charnockites and gneisses characterizes the northern block (NB), north of the Palghat-Cauvery lineament (PCL). The heat production of the upper, 7-10 km thick, metasomatized granulitic layer ranges between 0.2 and 0.75 mW m À3 (mean 0.5 ± 0.3 (SD) mW m À3 ). This layer overlies radioelement-depleted granulites characterized by very low heat production ranging from 0.14 to 0.2 mW m À3 (mean 0.16 ± 0.07(SD) mW m À3). In a large sector of the NB, erosion of the upper metasomatized granulite layer has laid bare the depleted granulitic rocks, which represent one of the lowest heat-producing crustal sections. The mean heat flow in the NB is 36 ± 4 mW m À2 (N = 10). The southern block (SB), south of PCL, in contrast to the NB, comprises complexly interlayered charnockites, gneisses, granites, khondalites, and leptynites, which have variable and much higher levels of heat production ranging between 1.11 and 2.63 mW m À3 . The heat flow in the SB is 47 ± 8 mW m À2 (N = 3). Overall, the range of heat flow values in the SGP is within the range for the DP. Mantle heat flow in the NB, both from the lowest heat-producing sector and other areas, is deduced in the light of heat production and heat flow data, at 23-32 mW m À2 , whose values are distinctly higher than 11-16 mW m À2for the adjacent DP. The higher mantle heat flow in the NB appears to be a consequence of higher heat production in the subjacent mantle.

This study examines the tectonic activity and structural features of active normal faults in the Weihe Graben, central China. The Weihe Graben is an area with a high level of historic seismicity, and it is one of the intracontinental systems that developed since Tertiary in the extensional environment around the Ordos Block. Analysis of high-resolution remote-sensing imagery data, field observations, and radiocarbon dating results reveal the following: i) active normal faults are mainly developed within a zone b500 m wide along the southern border of the eastern part of the Weihe Graben; ii) the active faults that have been identified are characterized by stepwise fault scarps dipping into the graben at angles of 40°-71°; iii) there are numerous discontinuous individual fault traces, ranging in length from a few tens of meters to 450 m (generally b 200 m); iv) fault zone structures, topographic features, and fault striations on the main fault planes indicate almost pure normal-slip; and v) late Pleistocene-Holocene terrace risers, loess, and alluvial deposits have been vertically offset by up to~80 m, with a non-uniform dip-slip rate (throw-rates) ranging from~2.1 to 5.7 mm/yr, mostly 2-3 mm/yr. Our results reveal that active normal faults have been developing in the Weihe Graben under an ongoing extensional environment, probably associated with the pre-existing graben and spreading of the continental crust, and this is in contrast with the Ordos Block and neighboring orogenic regions. These results provide new insights into the nature of extensional tectonic deformation in intracontinental graben systems.

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