Geochemical and geochronological studies of the Aketas granite from Fuyun County, Xinjiang: the implications of the petrogenesis and tectonic setting

Abstract

As the wall rock of the Aketas gold deposit, the Aketas granite is about 45 km away from Fuyun County, Xinjiang Province. The zircon weighted mean U–Pb age of the Aketas granite is 309.0 ± 4.7 Ma, indicating that the Aketas granite was emplaced during the late Carboniferous. The Aketas granite belongs to the High-K cal-calkaline series, with SiO2 content from 63.00 to 68.20 %, K2O content from 3.06 to 4.49 % and Na2O content from 4.14 to 6.02 %. The Alkaline Ratio (AR) of the Aketas granite is high, from 1.89 to 3.47, and is 2.95 on average. The Aketas granite has low ∑REE (92.42–122.73 ppm) and high ∑LREE/∑HREE ratios (6.54–11.88). For the trace elements, the Aketas granite is enriched in LILE (Rb, U, Th, K) and incompatible elements, and marked depleted in HFSE (Nb, Ta, P, Ti). The geochemical characteristics of the Aketas granite suggest that it is a typical I-type and volcanic arc granite, and that the crystallization of clinopyroxene and hornblende is notable during the magmatic evolution. In combination with the regional tectonic studies, we propose that the emplacement of the Aketas granite implies the Altai and East Junggar area was still dominated by a subduction system at ~309 Ma.