哈萨克斯坦阿克斗卡特大型斑岩铜矿床成矿时代与剥露历史研究

哈萨克斯坦阿克斗卡特大型斑岩型铜矿床产在中亚成矿域巴尔喀什成矿带阿克斗卡矿田。本文根据花岗岩类岩石的锆石U-Pb、40Ar/39Ar和裂变径迹(FT)热年代学研究,结合前人研究成果,给出了阿克斗卡斑岩铜矿床从深成岩浆活动、成矿作用、区域冷却到剥露作用的全过程。阿克斗卡矿床及附近花岗岩类锆石SHRIMPU-Pb定年结果,给出科尔达尔岩体早期英云闪长岩的结晶年龄为335.7±1.3Ma;主成矿期的含矿二长花岗斑岩结晶年龄为327.5±1.9Ma,反映了阿克斗卡矿床斑岩型铜成矿作用的年龄。花岗岩类角闪石、黑云母、钾长石40Ar/39Ar热年代学分别给出矿物冷却年龄为310.6Ma、271.5Ma和274.9Ma,进一步限定了深成斑岩型铜成矿作用的时代和区域冷却的历史。磷灰石FT测年数据揭示,受区域构造作用的影响,阿克斗卡铜矿田在晚白垩世(91～68.0Ma)发生地块的差异隆升和剥露作用。

Geochronology studies on metallogenesis and exhumation of super-large Aktogai porphyry copper deposit, Kazakhstan

The super-large Aktogay porphyry copper deposit is one of three porphyry copper deposits in Aktogay ore field in Balkhash metallogenic domain, Kazakhstan, Central Asia. Zircon SHRIMP, 40Ar/39Ar and fission track (FT) dating in this paper, together with metallogenic information from previous studies, reveals the whole thermo-history from the intrusion of plutons and porphyry copper metallogenesis, and regional cooling, to the exhumation of the deposits. Zircon SHRIMP dating of granitoids from Aktogay ore field gives the crystallization age of 335.7 ± 1.3 Ma for quartz diorite from Cole-Dahl intrusion body, and that of 327.5 ± 1.9 Ma for Cu-bearing porphyry granodiorite from Aktogay deposit. This means the main ore-forming stage of the Aktogay porphyry Cu deposit at 327.5 ± 1.9 Ma. 40Ar/39Ar thermochronology of hornblende, biotite, and K-feldspar from Aktogay ore field gives the mineral cooling ages of 310.6 Ma, 271.5 Ma, and 274.9 Ma, respectively, further constraining the porphyry Cu mineralization and regional cooling history. Apatite FT dating of granitoids gives low temperature cooling ages ranging from 91 Ma to 68.0 Ma, suggesting the differential uplifting and exhumation of the porphyry Cu deposits together with the granodiorite during the Late Cretaceous in Aktogay ore field.