安徽铜陵姚家岭锌金多金属矿床成岩成矿年代学研究

LA-ICPMS U-Pb zircon age and molybdenite Re-Os dating of Yaojialing large zinc-gold polymetallic deposit,Tongling, Anhui Province,China

姚家岭锌金多金属矿床位于铜陵断隆区与繁昌断凹区的过渡部位,是长江中下游成矿带新近发现的大型锌金多金属矿床,也是铜陵矿集区中迄今发现的首例大型锌金多金属矿床。在详细野外地质工作及室内研究的基础上,对姚家岭矿床花岗闪长斑岩体开展了LA-ICPMS锆石U-Pb定年工作,获得206Pb/238U加权平均年龄为141.4±1.7Ma(MSWD=0.78,n=19),代表成岩年龄;选取了该矿床金属矿物辉钼矿进行Re-Os同位素测年,获得模式年龄范围为141.2±2.1Ma^141.6±2.7Ma,平均年龄为141.4±2.4Ma,可代表热液成矿作用的时代,与成岩年龄一致。姚家岭锌金多金属矿床为早白垩世早期岩浆热液作用形成的,是铜陵断隆区燕山期大规模成矿作用的产物,铜陵断隆区具有进一步寻找锌金矿床的有利前景。

Yaojialing zinc-gold polymetallic ore deposit, located in the transitional area between the Tongling uplift region and the Fanchang fault basin, is a recently-discovered large zinc-gold deposit in the Middle-Lower Reaches of Yangtze River. It is the first large zinc-gold deposit in the Tongling uplift region. It has measured reserves of 1.2Mt of Zn averaging 3. 64%, as well as 50t of Au, and Cu, Pb and Ag as by-products. The orebodies of it have vein to lenticular shapes and commonly locate in the contact zone with Carboniferous-Triassic limestone and Early Cretaceous granodiorite porphyry intrusion or exist inside limestone xenoliths entrapped within the granodiorite porphyry intrusion. Ore minerals in the main orebodies are usually sphalerite, pyrite, galena, chalcopyrite, gold with minor amount of scheelite, bornite, molybdenite, limonite, tetrahedrite, bismuthinite and malachite. Calcite, garnet, quartz, K- feldspar, fluorite are the major gangue minerals, while sericite, epidote, diopside, wollastonite, kaolinite and apatite are accessory phases. Hydrothermal alteration is commonly associated with the sulfide metallogeny at Yaojialing deposit. Skarnization, silicification, carbonatization, sericitization, clayzation and potassic alteration are well recognized. A closely related granodiorite porphyry has a LAICPMS U-Pb zircon age of 141.4 ±1.7Ma （ MSWD =0. 78, n = 19）. Two molybdenite samples yielded Re-Os isotopic model ages of 141.2 ±2. 1Ma and 141.6 ±2.7Ma, consistent with the age of the granodiorite porphyry. The Yaojialing deposit formed as a result of hydrothermal processes during the Early Cretaceous and was also part of the large-scale metallogeny of the Tongling uplift region in the Yanshanian Period. It is revealed that there is a favorable prospect for searching zinc-gold deposit in Tongling uplift district.