黄陵基底穹隆北部石墨矿床成矿物质来源的地球化学约束

在黄陵基底穹隆北部已发现的几个大鳞片晶质石墨矿区中采取少量新鲜石墨样品(含少量大理岩围岩)进行了矿石岩相学及地球化学测试,通过相应分析、图解,探讨其成矿物质来源。该区石墨矿石赋存于黄凉河岩组(Pt1h)一套孔兹岩系内,主要矿石类型为石墨片岩及石墨片麻岩。根据其主微量元素及碳同位素分析,恢复矿石原岩为一套含炭质的(砂)泥质沉积岩,其固定碳质绝大多数来源于有机物而不是大理岩中的无机碳。根据矿层的元素组成及古地史证据,推测黄凉河岩组的蚀源区以野马洞岩组(Ar2y,拉斑玄武质)为主,东冲河片麻杂岩(Ar2D,花岗质)次之,而不是前人认为的单一"以花岗质岩石为蚀源区"。从供给源到成矿母岩的演化过程中,发生了强烈的地球化学变化,而不只是物质简单的机械转移。

Geochemical constraints on the source of ore-forming materials of graphite deposits in the northern part of Huangling basement dome

A few fresh graphite samples including a small amount of marble surrounding rock were taken from several large scale crystalline graphite mining areas in the north of Huangling basement dome for ore petrographic and geochemical analysis, and the source of ore-forming materials was discussed through corresponding analyses and diagrams. The graphite ore in this area occurs in a set of khondalite series of Huanglianghe Formation (Pt₁h), and the main ore types are graphite schist and graphite gneiss. According to the analyses of major and trace elements and carbon isotopes, the recovered ore protolith was a set of carbonaceous (sand) argillaceous sedimentary rocks, and the graphite carbon almost came from organic matter rather than from inorganic carbon in marble. According to the element composition and paleogeological evidence of the deposit, it is inferred that the source area of the Huanglianghe Formation was mainly Yemadong Formation (Ar₂y, tholeiitic), followed by Dongchonghe gneissic complex (Ar₂D, granitic), rather than the single "granitic rock as the source area" as previously thought. During the conversion process from the supply source to the ore-forming parent rock, strong geochemical changes took place rather than simple mechanical transfer of materials.