Zircon U-Pb and molybdenite Re-Os dating of the Liang-shan Mo deposit in Xinyu City, Jiangxi Province
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摘要:
良山钼矿是钦杭成矿带近年发现的大中型矿床,在矿化特征分析的基础上,对其进行了成岩成矿年代学研究。采用LAICP-MS锆石U-Pb测年技术,得到矿区内石英闪长斑岩的成岩年龄为168.2±2.3Ma。通过矿床辉钼矿Re-Os同位素分析,获得其等时线年龄为168.9±1.4Ma。指示成岩作用与成矿作用同时发生,含矿热液活动与岩浆活动有密切的关系,岩浆活动可能是形成良山钼矿床的重要因素。良山钼矿床的成矿时间与钦杭成矿带内华南燕山期第一阶段大规模多金属矿化时间(170Ma)吻合。良山钼矿床形成于同一区域成矿背景下,是区域构造岩浆作用的产物,为华南燕山期成矿作用的组成部分。
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关键词:
- 锆石U-Pb年龄 /
- 辉钼矿Re-Os年龄 /
- 斑岩型钼矿床 /
- 良山 /
- 钦杭成矿带
Abstract:The Liangshan molybdenum deposit was found in the western region of the Wugongshan-Qianshan subzone a few years ago. Based on an analysis of the mineralization features of the deposit, the authors determined LA-ICP-MS zircon U-Pb ages for the ore-bearing rocks in the Liangshan deposit. U-Pb dating of zircon by LA-ICP-MS reveals that the intrusion age of the Liang-shan porphyry granite is 168.2±2.3Ma. The 187Re and 187Os values of molybdenum from the molybdenum deposit were determined by the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Re-Os isochron of molybdenum suggests that the metallogenic epoch of the deposit is 168.9±1.4Ma, indicating that this deposit had a close relation with its host rocks, the magmatic activity had a close relationship with ore-bearing hydrothermal activities, and magmatic activity was an important factor for the formation of the Li-angshan molybdenum deposit. The metallogenic time of the Liangshan molybdenum deposit is consistent with south China first stage large-scale polymetallic mineralization of Yanshanian period (170Ma). The Liangshan molybdenum deposit was formed in the same regional metallogenic setting and resulted from regional tectonic magmatism, as a part of the South China Yanshanian mineralization.
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致谢: 野外采样及地质考察过程中得到江西地矿局赣西北地质大队王学军队长的大力协助和指导,审稿专家对本文提出了宝贵的意见和建议,在此表示诚挚的感谢。
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图 1 江西新余铁矿田区域地质简图(据参考文献[6]修改)
Q—第四系;Z1l—乐昌群老虎塘组;Z1b—乐昌群坝里组;Nh2xf2—杨家桥群下坊组上段;Nh2xf1—杨家桥群下坊组下段;Nh2g—杨家桥群古家组;γ5—燕山期石英闪长岩;γ4—印支二云母花岗岩;γ3—加里东期花岗闪长岩;F—断层及推测断层图;★—良山钼矿所在地
Figure 1. Geological map of the Xinyu iron orefield, Jiangxi Province
图 2 江西新余良山钼矿床地质简图(据参考文献[11]修改)
Nh2xf2—杨家桥群下坊组上段;Nh2xf1—杨家桥群下坊组下段;Nh2s—潭头群上施组;γδπ52—燕山期石英闪长斑岩;γ4—印支期黑云母花岗岩;Fe—铁矿层;Mo—钼矿体;1—勘探线及编号;7802—钻孔及编号;F—正断层
Figure 2. Geological map of the Liangshan molybdenum deposit in Xinyu County, Jiangxi Province
表 1 良山花岗岩体(DX011-01)锆石U-Pb同位素LA-ICP-MS分析结果
Table 1 LA-ICP-MS U-Pb data of zircons from the Liangshang granites
序号 同位素比值 同位素年龄/Ma 元素含量/10-6 Th/U 207Pb/206Pb 1σ 207Pb/235U 1σ 206Pb/238U 1σ 207Pb/235U 1σ 206Pb/238U 1σ Th U Pb 01 0.05048 0.000835 0.1814 0.00329 0.02598 0.000307 169.3 2.83 165.4 1.93 1680 7484 178 0.22 02 0.05152 0.000804 0.1817 0.00303 0.02551 0.000275 169.5 2.60 162.4 1.73 1792 6285 168 0.29 03 0.04964 0.000765 0.1794 0.00315 0.02614 0.000311 167.6 2.72 166.4 1.96 1885 6300 176 0.30 04 0.04841 0.000723 0.1782 0.00300 0.02660 0.000287 166.5 2.59 169.2 1.80 956 8452 158 0.11 05 0.05424 0.000871 0.2430 0.00456 0.03239 0.000411 220.9 3.73 205.5 2.57 1134 5801 162 0.20 06 0.05000 0.000834 0.1775 0.00321 0.02565 0.000273 165.9 2.77 163.3 1.72 2403 6830 200 0.35 07 0.05273 0.000879 0.1938 0.00385 0.02650 0.000321 179.9 3.28 168.6 2.02 2132 14208 307 0.15 08 0.04937 0.000924 0.1872 0.00372 0.02746 0.000346 174.3 3.19 174.7 2.17 1320 5389 139 0.24 09 0.04888 0.000812 0.1760 0.00319 0.02607 0.000315 164.6 2.76 165.9 1.98 1404 10589 205 0.13 10 0.04867 0.000795 0.1797 0.00342 0.02673 0.000354 167.8 2.95 170.1 2.22 1866 6410 175 0.29 11 0.05292 0.001050 0.3394 0.01086 0.04528 0.001236 296.7 8.24 285.5 7.62 712 2071 87 0.34 12 0.05306 0.001134 0.2000 0.00435 0.02726 0.000386 185.1 3.68 173.4 2.42 1689 5078 165 0.33 13 0.05420 0.000782 0.3503 0.00664 0.04665 0.000621 305.0 5.00 293.9 3.83 2454 4953 339 0.50 14 0.05248 0.000939 0.2692 0.00703 0.03689 0.000672 242.1 5.63 233.5 4.18 1480 4457 195 0.33 15 0.05785 0.000937 0.4196 0.00842 0.05259 0.000818 355.7 6.03 330.4 5.01 2339 4477 359 0.52 16 0.04913 0.000848 0.1749 0.00326 0.02581 0.000317 163.6 2.82 164.3 2.00 4040 7380 280 0.55 17 0.04966 0.000961 0.2105 0.00557 0.03067 0.000595 194.0 4.68 194.8 3.72 1507 4295 135 0.35 18 0.05360 0.000800 0.1968 0.00339 0.02661 0.000322 182.4 2.87 169.3 2.02 2163 8609 248 0.25 19 0.05798 0.001294 0.5659 0.01320 0.07096 0.000914 455.3 8.57 441.9 5.51 655 752 111 0.87 20 0.04693 0.000811 0.1751 0.00356 0.02707 0.000384 163.8 3.08 172.2 2.41 2022 4238 153 0.48 21 0.05059 0.000903 0.2060 0.00433 0.02949 0.000399 190.2 3.65 187.3 2.50 1767 3699 141 0.48 22 0.04956 0.000794 0.1813 0.00332 0.02654 0.000331 169.2 2.86 168.9 2.08 2282 6961 206 0.33 23 0.04849 0.000910 0.1846 0.00399 0.02759 0.000355 172.0 3.42 175.4 2.23 1497 4971 142 0.30 表 2 良山钼矿床辉钼矿Re-Os同位素测年结果
Table 2 Molybdenite Re-Os isotope test data sheet for the Liangshan deposit
样名 样重/g Re/10-6 C普Os/10-9 187Re/10-6 187Os/10-9 模式年龄/Ma JX52-3A 0.00505 230.2±3.4 3.2538±0.8432 144.7±2.2 407.6±3.3 168.9±3.3 JX52-3C 0.00227 343.9±2.8 0.0073±0.3172 216.2±1.7 609.4±3.9 169.0±2.4 JX52-3E 0.00559 86.7±6.6 0.0024±0.1076 54.51±4.1 154.0±0.9 169.4±2.3 JX52-5B 0.00217 538.9±5.7 0.0078±0.4228 338.7±3.6 953.2±6.6 168.7±2.7 JX52-6A 0.00222 239.0±2.4 0.0074±0.1597 150.2±1.5 421.0±2.6 168.0±2.6 JX52-6B 0.00202 380.7±4.1 0.0083±0.4506 239.3±2.6 680.0±4.8 170.3±2.8 注:普Os是根据Nier值的Os同位素丰度,通过192Os/190Os测量比计算得出,Re、Os含量的不确定度包括样品和稀释剂的称量误差、稀释剂的标定误差、质谱测量的分馏校正误差、待分析样品同位素比值测量误差,置信水平95%,模式年龄的不确定度还包括衰变常数的不确定度(1.02%),置信水平95%;Re-Os模式年龄按下列公式计算:t=1/λ{ln[1+N(187Os)/N(187Re)]};λ为187Re的衰变常数1.666×10-11/a(±1.02%)[24];t表示矿物形成后的年龄,在公式中单位为年(a) -
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