Molybdenite Re-Os Isotopic Dating of Xitian Deposit in Hunan Province and Its Geological Significance
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摘要: 湘东南锡田是近年来新发现的一个具有大型规模的钨锡多金属矿田,该矿田位于湘赣边界,南岭成矿带与钦杭成矿带的交汇部位,扬子地块与华夏地块的拼合带。目前对于矿体与成矿岩体之间的关系以及矿体形成时代的问题尚存争议,钨锡矿化究竟是与印支期还是与燕山期花岗岩有关,矿田中众多矿体是否同期形成,这些问题仍待进一步确定。本文选取了两个矿床,即山田云英岩-石英脉型锡多金属矿床和桐木山破碎带蚀变岩型锡多金属矿床,分别对来自这两个矿床的辉钼矿样品进行了Re-Os同位素定年,获得的Re-Os模式年龄分别为(158.9±2.2) Ma(2SD)和(160.2±3.2) Ma(2SD),表明这两个矿床形成于晚侏罗世早期。高精度的云母Ar-Ar和辉钼矿Re-Os年龄数据表明锡田钨锡多金属矿田的垄上、荷树下、山田、桐木山矿床均形成于150~160 Ma,即南岭与花岗岩有关钨锡多金属矿大规模成矿作用的高峰期。上述两个辉钼矿样品的铼含量分别为12.44×10-6和2.367×10-6,指示成矿物质分别为壳-幔混合来源和地壳来源,为准确认识该矿田的成矿物质来源提供了进一步的制约。本文还对南岭地区晚侏罗世与花岗岩有关的钨锡多金属矿中90个辉钼矿的铼含量数据进行了统计,结果表明钨锡多金属矿的成矿物质绝大多数为地壳来源,少数为壳-幔混合来源。Abstract: The Xitian large-scale W-Sn polymetallic ore field has been explored in recent years. It is found in jointed adjoining areas of the Nanling and Qinhang metallogenic belts which are located on the boundary between Hunan and Jiangxi provinces, and the junction of the Yangtze and Cathaysia blocks. At present, there are several debates about the formation ages of the ore bodies and nearby granitic intrusions. For example, is W-Sn mineralization related to either Indosinian or Yanshanian granites? Were numerous different types of ore bodies formed in the corresponding period? The separation of molybdenite minerals from two tin polymetallic deposits, Shantian greisen-quartz vein ore deposit and Tongmushan crushed zone-alterated rock ore deposit was undertaken and is reported in this paper. Re-Os model ages of molybdenite in these two deposits yielded (158.9±2.2) Ma (2SD) and (160.2±3.2) Ma (2SD), respectively, which show they were generated in the early stage of the late Jurassic period. According to statistical data of mica Ar-Ar and molybdenite Re-Os ages, Longshang, Heshuxia, Shantian and Tongmushan ore deposits were all formed during 150-160 Ma, which is the peak period of W-Sn large-scale mineralization related to granitic intrusions. Rhenium contents of the two molybdenite samples are 12.44×10-6 and 2.367×10-6, respectively, which suggests that metallogenic materials were derived from crustal-mantle mixture and crust. Combining with ninety data of rhenium contents in molybdenites of W-Sn polymetallic deposits closely related to granitoids in Nanling area in late Jurassic, the suggestion that a majority of metallogenic materials were derived from crust is given, with only a few of them derived from crust-mantle mixture.
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图 1 锡田钨锡多金属矿田在华南地区的位置图 (改编自徐先兵等[28])
Figure 1.
表 1 山田和桐木山矿床辉钼矿及标准物质JDC的Re-Os同位素分析结果
Table 1. Re-Os analytical results of molybdenites from the Shantian and Tongmushan ore deposits and reference materials JDC
样品名称 样品编号 样品质量m/mg w(Re)/10-6 w(普Os)/10-9 w(187Os)/10-6 w(187Os)/10-6 模式年龄/Ma 测定值 2SD 测定值 2SD 测定值 2SD 测定值 2SD 测定值 2SD 山田 ST-01 200.56 12.44 0.10 0.050 0.006 7.816 0.061 20.72 0.17 158.9 2.2 桐木山 TMS-02 202.61 2.367 0.037 0.003 0.002 1.488 0.024 3.977 0.037 160.2 3.2 标准物质 JDC 50.01 17.09 0.14 - - - - 25.15 0.20 141.0 1.9 表 2 南岭地区晚侏罗世钨锡多金属矿床的Ar-Ar和Re-Os年龄统计
Table 2. Ar-Ar and Re-Os mineralization ages related to W-Sn polymetallic deposits in the Nanling area on late Jurassic
矿床名称 省份 云母Ar-Ar法定年的年龄/Ma 参考文献 辉钼矿Re-Os法定年的年龄/Ma 参考文献 八仙脑钨矿 江西 165.7±1.3,59.8±1.1,143.5±1.4 曾庆涛等[40] - - 漂塘钨矿 江西 155.0±2.4~158.9±1.4 张文兰等[41] - - 柯树岭钨锡矿 江西 158.8±1.2 刘善宝等[42] - - 大吉山钨矿 江西 144.4±0.5,147.2±0.6 张文兰等[43] - - 张天堂钨矿 江西 - - (155.2±2.3)~(156.5±2.1) 丰成友等[44] 牛岭钨锡矿 江西 - - 154.9±2.6,154.6±9.7 丰成友等[45] 樟斗钨矿 江西 - - 149.1±7.1 丰成友等[45] 浒坑钨钼矿 江西 - - 150.2±2.2 刘珺等[46] 淘锡坑钨矿 江西 - - 154.4±3.4 陈郑辉等[47] 芙蓉锡矿 湖南 154.8~160.1,150.6~157.3 毛景文等[48] - - 150.6±1.0,159.9±0.5,154.8±0.6 彭建堂等[49] - - 新田岭钨矿 湖南 156.1±0.4 毛景文等[37] - - 香花岭锡矿 湖南 154.4±1.1,160±1.2,158.7±1.2 Yuan等[50] - - 柿竹园钨锡多金属矿 湖南 153.4±0.2 毛景文等[37] 151.0±3.5 李红艳等[51] 瑶岗仙钨矿 湖南 - - (152±3.5~(161.1±4.5) Peng等[52] - - (153±7)~(163.2±4.2) Wang等[53] 159.0±1.5 毛景文等[54] 161.3±2.1 毛景文等[54] 黄沙坪铅锌铜钨锡矿 湖南 - - 154.2±2.2 姚军明等[55] - - 153.9±1.7,154.2±2.2 毛景文等[54] - - 153.8±4.8 马丽艳等[56] - - 159.4±3.3,57.5±2.4,157.6±2.3 雷泽恒等[57] 九嶷山大坳锡矿 湖南 - - 151.4±2.4 付建明等[58] 锡田锡多金属矿 湖南 155.6±1.3,157.2±1.4 马丽艳等[15] 150.0±2.7 刘国庆等[18] 行洛坑钨钼矿 福建 - - 156.3±4.8 张家菁等[59] 石人嶂钨矿 广东 - - 154.2±2.7 付建明等[60] 师姑山钨铋矿 广东 - - 159.1±2.2 付建明等[60] 注:“-”表示暂无此数据。 表 3 南岭地区晚侏罗世钨锡多金属矿床辉钼矿中铼含量统计
Table 3. The molybdenite Re contents of W-Sn polymetallic deposits in the Nanling area on late Jurassic
矿床名称 省份 辉钼矿Re-Os法定年的年龄/Ma 辉钼矿中铼含量 参考文献 柿竹园钨锡多金属矿 湖南 151.0±3.5 1.040×10-6~1.340×10-6 李红艳等[51] 瑶岗仙钨矿 湖南 (152±3.5)~(161.1±4.5) 1.016×10-8~2.618×10-6 Peng等[52] 153±7 5.436×10-8~4.895×10-7 Wang等[53] 163.2±4.2 9.025×10-7~4.909×10-6 黄沙坪铅锌铜钨锡矿 湖南 154.2±2.2 0.460×10-6~2.590×10-5 姚军明等[55] 153.8±4.8 3.107×10-6~4.683×10-5 马丽艳等[56] 159.4±3.3 4.347×10-7~2.171×10-5 雷泽恒等[57] 157.5±2.4 1.175×10-6~1.192×10-5 157.6±2.3 5.890×10-7~1.743×10-5 九嶷山大坳锡矿 湖南 151.4±2.4 2.933×10-8~1.175×10-6 付建明等[58] 锡田荷树下锡矿 湖南 150.0±2.7 1.739×10-8~2.838×10-7 刘国庆等[18] 行洛坑钨钼矿 福建 156.3±4.8 2.851×10-6~4.292×10-6 张家菁等[59] 石人嶂钨矿 广东 159.1±2.2,157.6±1.6 4.843×10-7~5.039×10-6 付建明等[60] 师姑山钨铋矿 广东 154.2±2.7,154±2 5.773×10-7~1.495×10-6 付建明等[60] 注: 辉钼矿中铼含量统一格式为小数点前为一位数,保留四位有效数字。 -
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