河北撒岱沟门钼矿床成矿流体演化研究

Study on Evolution of Ore-forming Fluid in the Sadaigoumen Molybdenum Deposit,Hebei Province

撒岱沟门钼矿床是华北地台北缘燕辽钼(铜)成矿带上典型的斑岩型钼矿床,位于河北省丰宁县境内,是该区目前发现的最大钼矿床。矿床成矿作用可划分为3期:成矿前(无矿石英脉阶段)、成矿期((1)石英+磁铁矿+辉钼矿+黄铁矿+钾长石阶段,(2)石英+辉钼矿阶段,(3)石英+云母+辉钼矿+黄铁矿阶段,(4)石英+辉钼矿+黄铁矿阶段)、成矿期后(晚期无矿热液阶段)。对矿床流体包裹体的研究表明,撒岱沟门钼矿床主要发育两类包裹体:盐水溶液包裹体和含CO_2三相包裹体。成矿前与成矿期后流体以气液两相的盐水溶液包裹体为主,对应的均一温度、盐度分别为248~296℃和6.0%~10.2%NaCleqv,以及130~197℃和0.2%~5.9%Na Cleqv。成矿期两种类型包裹体均发育,均一温度和盐度主要集中在200~260℃和7.0%~17.5%NaCleqv。成矿流体中气相成分以CO_2、H_2O、N_2为主,离子以Na^+、Ca^(2+)、NO_3^-和Cl^-为主。氢、氧同位素研究表明,撒岱沟门钼矿床中石英的δD值为-88‰^-102‰,δ^(18)OH_2O值为-1.90‰~3.12‰,成矿流体属于以岩浆水为主的中低温中低盐度的CO_2-H_2O-NaCl体系。

The Sadaigoumen Mo deposit is a typical porphyry Mo deposit in the Yan-Liao Mo（ Cu） metallogenic belt on the northern margin of North China Block. Located in Fengning County,Hebei Province,the Sadaigoumen Mo deposit is the largest molybdenum deposit in this region so far. The Mo mineralization can be divided into three periods,which are pre-ore period（ quartz vein stage without mineralization）,the syn-ore period（ including（1）quartz ＋ magnetite ＋ molybdenite ＋ pyrite ＋ K-feldspar stage,（2）quartz ＋ molybdenite stage,（3）quartz＋ mica ＋ molybdenite ＋ pyrite stage,and（4）quartz ＋ molybdenite ＋ pyrite stage）,and the post-ore period（ late hydrothermal stage without mineralization）. In order to explore the ore-forming mechanism of this Mo deposit,the study on ore fluid was carried out in this paper. There are two types of fluid inclusions in this deposit,which consist of two-phase vapor-liquid inclusions and CO2-bearing three-phase inclusions. The quartz from the preore and post-ore periods are predominantly characterized by the two-phase vapor-liquid inclusions,which have the homogenization temperatures ranging from 248 to 296 ℃,130 to 197 ℃,and the salinities varying from 6. 0% to 10. 2% NaCleqv,and 0. 2% to 5. 9% NaCleqv for the pre-ore and post-ore periods,respectively.During the syn-ore period,the two types of fluid inclusions are both developed in quartz,with the homogenization temperatures and salinities ranging from 200 to 260 ℃,and from 7. 0% to 17. 5% NaCleqv. Raman spectrum and inclusion groups components studies indicate that ore fluids are mainly composed of CO2,H2O,N2,Na＋,Ca2＋,NO3- and Cl-. The δD and δ-（18）OH2O values for quartz from ores vary from -88‰ to -102‰,and-1. 90‰ to 3. 12‰,respectively. Therefore,the ore fluid in the Sadaigoumen Mo deposit is a CO2-H2ONaCl system dominated by the magmatic water in a medium-low temperature and medium-low salinity.