中甸弧燕山晚期成矿事件的Re-Os定年及成矿规律研究

Re-Os dating for ore-forming event in the late of Yanshan Epoch and research of ore-forming regularity in Zhongdian Arc.

中甸弧是义敦岛弧的南延部分,是我国重要的铜铅锌钼多金属成矿区。在该地区,相对于印支期成矿事件,燕山晚期成矿事件的研究程度和重视程度均不够。中甸弧燕山晚期形成的矿床主要为休瓦促钨钼矿床、热林多金属矿点和红山多金属矿床。本文通过辉钼矿Re-Os定年技术,精确确定休瓦促矿床形成于83±1Ma,热林矿点形成于81.2±2.3Ma。同时通过刘兴旺等(2006)的辉钼矿Re-Os年龄(77±2Ma),并参考黄铁矿Re-Os测试结果(75±18Ma),可推断红山矿床主要形成发生于燕山晚期。根据上述定年结果,中甸弧成矿作用表现出一定的规律性:休瓦促→热林→红山,三矿床(点)具有成矿年代相近、空间等距、矿种由高温组合向低温组合变化、矿化类型相似、成矿母岩体就位深度递增等特点。这是同一构造-岩浆-成矿作用连续演化的结果。依据上述成矿规律,在中甸弧北部具有一定的找矿前景。

The Zhongdian arc, which is the southward extension of the Yidun island arc, is an important Cu-Pb-Zn-Mo polymetallic metallogenic province in China. In this region, compared with the Indosinian metallogenic event, the late Yanshanian metallogenic event and ore deposits such as the Xiuwacu Wu-Mo deposit, Relin polymetallic occurrence and Hongshan polymetallic deposit formed in the area in this period are less studied. By using the molybdenite Re-Os dating technique, it was accurately determined that the Xiuwacu ore deposit and Relin ore occurrence formed at 83 +/- 1 Ma and 81.2 +/- 2.3Ma respectively. According to the molybdenite Re-Os age (77 +/- 2Ma) for altered granite and quartz vein type orebodies and the pyrite Re-Os age (75 +/- 18Ma) for the skarn type orebodies, it may be inferred that the Hongshan deposit formed mainly in the late Yanshanian. Based on the above-mentioned dating results, the metallogenic characteristics shown by mineralization of the Zhongdian arc may be summarized as follows: the Xiuwacu, Relin and Hongshan deposits (occurrences) are characterized by close mineralization ages, equal spacing, change of metallic minerals from the high-temperature to moderate-temperature mineral assemblages, similar mineralization types and progressive increase of the emplacement depth of their host rocks. These metallogenic characteristics are the result of the continuous evolution of the same tectonomagmato-mineralization. The aforesaid metallogenic characteristics show that the northern part of the Zhongdian arc has relatively good ore prospects.