Pyrite Re–Os and zircon U–Pb dating of the Tugurige gold deposit in the western part of the Xing'an–Mongolia Orogenic Belt, China and its geological significance

Abstract

The Tugurige gold deposit, in the northeastern margin of the North China Craton (NCC) and western part of the Xing'an–Mongolia Orogenic Belt (XMOB), is a large tonnage quartz-vein type deposit with a resource of ~24t at about 4g/t Au. Gold mineralization is hosted by porphyritic syenogranite and controlled by NW-trending faults. Our study provides the first precise age for the Tugurige gold mineralization and host porphyritic syenogranite. The U–Pb age of zircons from the syenogranite is 276±2Ma, and Re–Os dating of six pyrite separates from the deposit yields an isochron age of 268±15Ma. The results show that the ages of syenogranite and gold mineralization are the same within error. Furthermore, geological and geochronological evidence indicate that the syenogranite and gold mineralization have very close genetic relationships and that they are products of Permian magmatism related to post-collisional extension of the Central Asian Orogenic Belt (CAOB). The initial Os isotopic compositions (187Os/188Os=1.26±0.69) of pyrite indicate that the source of Os, and by inference other ore-related materials, are derived from the crust. The Late Paleozoic is an important period in which economic gold mineralization was deposited in the CAOB.