黑龙江争光金矿床年代学特征及成矿意义

Chronological Characteristics and Metallogenic Significance of Zhengguang Gold Deposit,Heilongjiang Province,China

多宝山斑岩矿床位于兴蒙褶皱带的东段,是中国东北部著名的超大型斑岩铜矿床,具有极大的找矿潜力。争光矿床处于多宝山多金属成矿带的南东端,是区内重要的金矿床。本文对争光金矿区多宝山组灰绿色凝灰岩中因受闪长玢岩侵入影响而形成的薄膜状辉钼矿,进行Re-Os同位素定年,获得加权平均年龄为480±3Ma;对采自于接触部位内侧的闪长玢岩(侵入安山岩,赋存金矿体),以及采自于一条被金矿脉切断的岩脉中的闪长岩,进行锆石U-Pb定年,获得^(206)Pb/^(238)U加权平均年龄分别为478.3±3.7Ma、150.67±0.77Ma。根据多宝山矿集区的地质背景、区内经历的对岩浆活动与成岩成矿有重要影响的加里东期、海西期和燕山期的三大构造-热事件的演化过程、多宝山斑岩成矿系统中Au元素的含量、花岗闪长斑岩具有的黄铁绢英岩化、碳酸盐化和多金属硫化物矿化、矿区发现了隐爆角砾岩型矿石,以及多宝山、铜山、争光Re-Os同位素较为一致的测年结果等诸多特征,推断争光金矿早期矿化发生在加里东期,为多宝山斑岩成矿系统外围的浅成低温热液型矿化,并与闪长玢岩岩浆活动相关,后期叠加了燕山期闪长岩岩浆活动的成矿作用。本文所测辉钼矿中Re的较高含量(295.9×10^(-6)~394.7×10^(-6)),推测其成矿物质主要来源于地幔,并含有部分地壳物质。

The Zhengguang gold deposit is located in the southeast segment of the Duobaoshan polymetallic metallogenic belt,which is one of the largest ore deposit clusters inHeilongjiang Province, NE China and situated in the east segment of the Xing＇ an-Mongolia fold belt. In this study, The rock from which the molybdenite sample was collected is greyish green tuff, belong to Duobaoshan Formation, and is Mineralized due to the diorite porphyrite intrusion. The molybdenite is film-like, the molybdenite Re-Os isotopic dating for the Zhengguang gold district yielded weighted mean age of 480±3 Ma, and the zircon U-Pb dating on the diorite-porphyrite that is taken from the intrusive contact area of diorite and diorite- porphyrite（occurrenee of gold orebodies） and diorite that is collected from a diorite vein cut by gold veins yielded 206Pb/238U weighted mean ages of 478.3±3.7 Ma and 150.67±0.77 Ma, respectively. According to geological background of Duobaoshan deposit clusters, Duobaoshan area witnessed the Caledonian, Hercynian and Yanshanian major tectonothermal events which exerted a significant influence on the magmatic activities and metallogenesis, the content of Au element of Duobaoshan porphyry metallogenic system, the granodiorite-porphyry body exhibiting obvious beresitization, carbonatization and polymetallic sulfide mineralization, cryptoexplosive breccia type ore had been found in the district and basically consistent with the Re-Os ages of the Duobaoshan,Tongshan and Zhengguang deposits, we infer that the early mineralization in the Zhengguang gold deposit occurred in Ordovician and was dominantly epithermal mineralization in the peripheral areas of the Duobaoshan porphyry metallogenic system related to diorite- porphyrite magmatic activities, and that the late mineralization in the deposit experienced metallogenesis of the Late Jurassic diorite magmatic activities. Therefore, the Zhengguang gold deposit is the product of multi-stage metallogenesis related to diorite-porphyrite and diorite. In addition, based on higher content of Re （295.9 × 10-6 ～394.7 × 10-6） in the molybdenite measured, we predict that the ore-forming materials were dominantly derived from the mantle, and contained some crustal materials.