摘要
内蒙古哈达庙金矿床位于天山—内蒙海西晚期褶皱带镶黄旗复向斜内。金矿化主要分布在燕山期花岗斑岩与石英闪长岩接触带以及邻近的火山角砾岩脉群内,矿体主要由含金石英脉和含金石英-电气石脉组成,金矿石品位较高。围岩蚀变自含金矿脉向外分别为硅化、电气石化、钾化、绿帘石化和碳酸盐化,金矿化同硅化和电气石化有关。硫、碳、氧和氢同位素数据以及黄铁矿痕量元素分析表明:同斑岩体有关的金矿化和在火山角砾岩脉群中产出的金矿化是同源不周演化阶段的产物,高f_(o2)和低pH值的物理化学环境是金沉淀富集的重要控制因素,矿床成因类型属斑岩型中温热液矿床。
Situated in Xianghuangqi synclinore of Late Hercynian Tianshan-Inner Mongolian folded belt, the Hadamio gold deposit consists of two major orebodies which are now being exploited. One is composed of quartz, tourmaline, chalcopyrite, pyrite, magnetite, native gold and electrum and occurs extensively along the contact zone between the Hadamio granite porphyry and quartz diorite, associated with silicification, tourmalinization and beresitization; the other, which has the same mineral assemblage, is distributed inside the volcanic breccia dykes and associated with silicification, tourmalinization and epidotization. Of these wall-rock alterations, silicification and tourmalinization are intense and have close relationship with gold mineralization. The gold-bearing granite porphyry outcrop is about 80m long and 40m wide, trending west-east and dipping laterally in north and south directions. The major minerals include quartz, microperthite(Or_(87)Ab_(13) , plagioclase(An=15-10) and biotite, the phenocrysts consist of K-feldspar, quartz and plagioclase, and accessory minerals are apatite, magnetite, sphene, zircon and hematite. The porphyry is characterized petrochemically by an average SiO_2 of 71.92% and K_2O+Na_2O of 6.74% (with K_2O/Na_2O ratio being 1), thus belonging to normal calc-alkaline rock series. A number of gold-bearing volcanic breccia dykes have been discovered around the Hadamio gold-bearing granite porphyry. Breccia dykes consist of granodiorite fragments, cataclastic quartz diorite and volcanic cements and have an average SiO_2 of 72.31% and K_2O+Na_2O of 2.54%, with K_2O/Na_2O ratio being 0.5. The formation temperatures of minerals vary from 400℃to 120℃ with those of the main ore-forming stage ranging from 190℃ to 282℃, averagely 210℃. According to the homogeneous temperature of fluid inclusions in quartz and formation sequence of minerals, the gold mineralization might be divided into four stages, i. e., quartz+tourmaline; quartz+chalcopyrite;polymetallic sulfides and carbonate+quartz. Oxygen, hydrogen, carbon and sulfur isotopic compositions suggest that δ^(18)O values of quartz from gold orebodies at the contact zone vary in a relatively narrow range(+9.8-13.5%) , δ^(18)O_(H_2o) values of equilibrium water are+4.8 -+6.9‰,δD values of fluid inclusion water in quartz are-46--58‰,and δ^(34)S values of pyrite are +1.9-+2.6‰.The volcanic breccia dykes are characterized by mixed solutions with magmatic water as the major source. The stable isotope compositions are δ^(18)O=+6.5-+9.0‰, δ^(18)O_(H_2o)= + 1.1----+3.7‰, and δD=-44--48‰, and the δ~13(13)C value(+7.1‰)of calcite is approximately equal to that of the gold orebody at the contact zone. The variation range of stable isotope values together with the behavior of minor elements in pyrite implies that sulfur, oxygen, carbon and some metallic elements were largely derived from igneous sources at depth. All the data mentioned above suggest that the granitoids originated from the anatexis of early Paleozoic eugeosynclinal volcanic-sedimentary rocks. Moreover, the gold-bearing porphyry and gold-dearing volcanic breccia dykes are products of the evolution of the same magmatic hydrothermal fluid at different stages. It is therefore considered that the studied gold deposit belongs genetically to the mesothermal gold deposit.
出处
《矿床地质》
CAS
CSCD
北大核心
1989年第2期51-60,共10页
Mineral Deposits
