大兴安岭南段热液脉状矿床的流体包裹体和稳定同位素特征:对矿床成因的启示

大兴安岭南段发育大井、双尖子山、布金黑、拜仁达坝、维拉斯托等多个具有典型后生特征的热液脉状铅锌银锡多金属矿床。为了查明上述矿床在成矿流体、成矿物质等方面的特征与差异,进而总结大兴安岭南段热液脉状矿床成矿作用特点,本次研究在野外地质调研的基础上,对上述矿床进行了流体包裹体、激光拉曼和氢氧硫同位素的研究,并取得了如下主要的认识:(1)双尖子山银多金属矿床成矿流体属简单盐水体系热液,维拉斯托和布金黑矿床成矿流体属富碳质盐水体系热液,而大井铜矿成矿流体则为含子矿物的不均匀盐水体系热液;(2)大井、布金黑、拜仁达坝和维拉斯托等矿床早期成矿流体均来自于岩浆热液,但布金黑、拜仁达坝和维拉斯托矿床成矿流体在运移过程中明显地受到了大气降水和地层中有机质的影响;(3)大兴安岭南段多数热液脉状多金属矿床矿石硫同位素δ34S值具有岩浆来源特点,个别矿床硫同位素δ34S值偏高可能是由复杂的岩浆源区性质及地层硫混入所引起。总的来说,大兴安岭南段不同热液脉状矿床在物质来源和流体演化方面的差异明显,而这也体现了该区中生代热液成矿作用的多样性和复杂性特点。

Characteristics of Fluid Inclusions and Stable Isotopes of the Hydrothermal Vein-type Deposits in Southern Great Xing’an Range,China: Implications for the Genesis of the Deposits

Several hydrothermal vein-type deposits, including Dajing Sn-Cu poly-metallic deposit, Shuangjianzishan Ag polymetallic deposit, Bujinhei Pb-Zn deposit, Bairendaba Ag-Pb-Zn deposit and Weilasituo Sn-Cu polymetallic deposit, were developed in the southern Great Xing’an Range. In order to further understand the characteristics and differences of the ore-forming fluids and ore-forming materials from the hydrothermal vein-type deposits in this area, we carried out studies of fluid inclusions, Laser Roman, and H-O-S isotopes on the basis of field geological investigations. The results show that:（1）Ore-forming fluids of Shuangjianshan deposit belong to simple brine system, ore-forming fluids of Bujinhei and Weilasituo deposit belong to carbonaceous-rich brine system,and the initial ore forming fluids of Dajing deposit belong to daughter mineral bearing fluids, respectively;（2）Ore-forming fluids of early stage from Dajin, Bujinhei, Bairendaba and Weilasituo deposit were mainly derived from magmatic fluids, while the fluids were affected by meteoric water and organic matters.（3）The δ34S values of different hydrothermal vein-type deposits change around 0‰, and show the characteristics of deep source magma. Different magmatic sources and the involvement of the strata sulfur during mineralization may be the main cause for the differences of sulfur isotope composition among deposits. Generally, there exist obvious differences in terms of material sources and fluid evolution among different hydrothermal vein deposits in southern Great Xing’an Range, which reflects the diversity and complexity of the Mesozoic hydrothermal mineralization in-this area.