造山型金矿成矿流体来源与演化的氢-氧同位素示踪:夹皮沟金矿带例析  

Origin and evolution of ore fluid for orogenic gold traced by D-O isotopes: A case from the Jiapigou gold belt,China

作　　者：杨利亚[1] 杨立强[1] 袁万明[1] 张闯[1] 赵凯[1] 于海军 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中铁资源地质勘查有限公司,北京100039

出　　处：《岩石学报》2013年第11期4025-4035,共11页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(41230311);北京市优秀博士学位论文指导老师科研项目(20111141501);教育部新世纪优秀人才支持计划(NCET-09-0710);高等学校学科创新引智计划(B07011)联合资助

摘　　要：在详细的矿床地质研究和成矿阶段划分基础上,系统采集了距夹皮沟断裂带100~3622m的6个金矿床不同成矿阶段的20件矿石样品,进行了氢、氧同位素测试。距夹皮沟断裂带由近及远,各金矿床的氢、氧同位素组成分别为:北沟(100~172m,δD=-97‰^-90‰,δ18O w=-3.26‰~5.49‰)、二道沟(820~830m,δD=-95‰^-94‰,δ18O w=-4.58‰^-0.50‰)、三道岔(1385~1412m,δD=-97‰^-91‰,δ18O w=-3.58‰^-1.39‰)、四道岔(2776~2802m,δD=-99‰^-80‰,δ18O w=0.75‰~4.69‰)、八家子(3400m,δD=-102‰,δ18O w=0.22‰)、夹皮沟本区(3595~3622m,δD=-108‰^-92‰,δ18O w=2.91‰~5.39‰)。成矿早、主、晚阶段δD、δ18O w和W/R值分别为-97‰^-80‰、3.99‰~5.49‰和约0.1;-108‰^-90‰、-3.26‰~4.71‰和0.1~0.5;-97‰^-91‰、-4.58‰^-2.68‰和0.01~0.1。反映金矿早阶段成矿流体以变质水为主体,混入有少量岩浆水,W/R值较小;主阶段成矿流体为变质水和大气降水的混合,W/R值显著增大,氢、氧同位素和W/R值具有明显的空间不均一特征(成矿流体隧道式流动):前者与距夹皮沟断裂带的距离正相关、后两者负相关,而它们与各金矿床已探明资源量的相关性相反,可能表征了成矿系统有效流体压力对W/R值和金沉淀成矿的控制作用;晚阶段大气降水大量加入,成矿流体弥散式的流动机制引起大面积同位素均一化,W/R值最小。据此推断,氧同位素低值区与氢同位素和W/R高值区(尤其是它们的显著变化区)的套合部位是金大规模沉淀聚集的最有利地段暨找矿勘查的重要选区。Based on detailed studies on deposit geology and mineral paragenetic stages of the Jiapigou gold belt, 20 samples formed at different ore stages were systematically collected from six gold mines with varying distances of 100 - 3622m from the Iiapigou fault zone for hydrogen and oxygen isotopic analyses. The Beigou mine, about 100 - 172m away from the fault zone, shows 8D values of -97‰ - -90‰ and BTM Ow values varying from -3.26‰ to 5. 49‰; located about 820 -830m away from the fault zone, the Erdaogou mine yields isotopic values of -95‰ - -94‰ for hydrogen and -4.58‰ - -0. 50‰ for oxygen; the hydrogen isotopes are -97‰ - -91‰ and oxygen isotopes are -3.58‰ - - 1.39‰ for the Sandaocha mine with a distance of 1385 - 1412m away from the fault zone; the Sidaocha mine, 2776 N 2802m away from the fault zone, shows 8D values of -99‰ - -80‰ and 8TM Owvalues of 0. 75‰ - 4. 69‰; the isotope analyses for one sample from the Bajiazi mine （about 3400m away from the fault zone） yield 8D value of - 102‰ and 81SOw value of 0. 22‰; the Jiapigou mine （3595 -3622m away from the fault zone） exhibits 8D values of - 108‰ - -92‰ and t5ts OW values of 2. 91‰ N 5.39‰. At the early ore stage, this deposit belt displays a wide range of 8D values varying from -97‰ to -80‰ and a narrow range of positive δ18Ow values （3.99‰ -5.49‰）, with W/R ratio of at 0. 1 ; the main ore stage is characterized by more negative 8D values （ - 108‰ - -90‰）, widely varying δ18Ow values （ -3.26‰ - 4. 71‰） and high W/R ratios （0. 1 -0. 5） ; the late ore stage has a narrow range of δD values （ -97‰ - -91‰）, negative but concentrated δ18Ow values （ -4. 58%0 - -2. 68%0） and low W/R ratios （0. 01 N0. 1 ）. The ore fluids at the early ore stage are dominated by metamorphic fluids mixed with minor amounts of magmatic fluids, and are featured by small W/R ratios. During the main ore stage, the ore fluids are the mixture by metamorphic and atmospheric fluid with high W

关 键 词：氢-氧同位素 成矿流体来源与混合 水 岩交换 成矿机制 夹皮沟金矿带 

分 类 号：P597.2[天文地球—地球化学] P618.51[天文地球—地质学]