| 特提斯喜马拉雅金锑铅锌多金属成矿带成矿流体特征:来自H-O同位素的约束 |
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| 引用本文： | 梁维.特提斯喜马拉雅金锑铅锌多金属成矿带成矿流体特征:来自H-O同位素的约束[J].地球科学,2019,44(7):2308-2318. |
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| 作者姓名： | 梁维 |
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| 作者单位： | 中国地质调查局成都地质调查中心, 四川成都 610081 |
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| 基金项目： | 国家重点研发计划项目2016YFC0600308西藏山南地区铍锡多金属矿调查评价项目DD20190147国家重点研发计划项目2018YFC0604103国家自然科学基金41702080 |
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| 摘 要： | 特提斯喜马拉雅成矿带产出数十个规模不等的金矿、锑金矿、锑矿和铅锌多金属矿，近期的矿产勘查在片麻岩穹窿发现了铍稀有多金属矿床.该成矿带内发育两期金锑铅锌矿化，其一为以邦布金矿和马攸木金矿为代表的造山型金矿，形成于59~45 Ma，属于青藏高原造山主碰撞阶段的产物；其二为以姐纳各普金矿、车穷卓布锑矿、扎西康铅锌矿的晚期矿化和吉松铅锌矿等为代表的热液型矿化，集中形成于21~12 Ma的后碰撞造山阶段.大量的流体包裹体研究表明喜马拉雅金锑铅锌成矿带的成矿流体主要为中低温(小于300℃)、中低盐度流体(< 10% NaCleqv).本文统计了已发表的和新获得的带内不同类型矿床共169个石英、绢云母、菱锰矿等热液矿物氢氧同位素数据，发现在δ18OH2O-δDV-SMOW相图中，这些同位素组成构成了3个端元:A端元以车穷卓布锑矿为代表，显示出极低的δ18OH2O值(低于-13‰)和低的δDV-SMOW值(< -111‰)，靠近现代雨水线，完全落入西藏地热水H-O同位素范围；B端元以沙拉岗锑矿为代表，显示出具有最低的δDV-SMOW值(最低至-172‰)和较高的δ18OH2O值(高达12‰)，落入建造水的H-O同位素范围内；端元C以邦布金矿和浪卡子金矿为代表，显示出具有极高的δDV-SMOW值(高达-43‰)和中等的δ18OH2O值，与造山型金矿氧同位素6‰~13‰的范围相同，包括了原始岩浆水的范围和部分变质水的范围.带内主要金属矿床成矿流体氢氧同位素均介于这3个流体端元之间，显示出绝大部分矿床的流体均非单一流体来源，而具有多源流体混合的特征.
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| 关 键 词： | 特提斯喜马拉雅 多金属成矿带 氢氧同位素 成矿流体 矿床地质 |
| 收稿时间： | 2019-01-30 |
Characteristics of Ore-Forming Fluids in Himalayan Au-Sb-Pb-Zn Polymetallic Belt: Constraints from H-O Isotopes |
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| Abstract: | The Tethys Himalayan metallogenic belt contains dozens of gold, gold-antimony and lead-zinc polymetallic ore deposits with variable sizes. Some Be-Rb-Sn-W polymetallic deposits in the gneiss dome have been found in recent mineral explorations. A 2-stage gold-antimony-lead-zinc mineralization in the orogenic belt has been recognized, one of which is the orogenic gold deposit represented by the Bangbu and Mayum gold deposit. These deposits were formed at 59-45 Ma, belonging to the main collision stage of the India-Asia continental collision. The others are hydrothermal-type gold-antimony-lead-zinc deposits represented by the Jienagepu gold deposit, Cheqiongzhuobu vein-type antimony deposit, Zhaxikang lead-zinc polymetallic vein-type deposit and Jisong lead-zinc deposit. The formation of the deposits is concentrated in the post-collision orogenic stage of 21-12 Ma. A large number of fluid inclusion researches indicate that the ore-forming fluids of Himalayan gold-antimony-lead-zinc metallogenic belt are mainly medium-low temperature (less than 300℃) and medium-low salinity fluid (< 10% NaCleqv). This paper presented a total of 169 H-O isotopic data of quartz, sericite and rhodochrosite that have been published and newly obtained from experiments. It is found that these isotopic compositions constitute three endmembers in the δ18OH2O-δDV-SMOW phase diagram. The endmember A (the Cheqiongzhuobu-type) has characteristics of very low δ18OH2O value (< -13‰) and low δDV-SMOW value (< -111‰, which is close to the Modern Rainwater Line(MRL), and completely falls into the H-O isotope range of Tibet geothermal water. The endmember B (the Shalagang-type) shows the lowest δDV-SMOW value (lowest to -172‰) and higher δ18OH2O (up to 12‰) value than A, that falls within range of the Formation Water. The endmember C constitutes very high δDV-SMOW value (up to -43‰) and a medium δ18OH2O value, which has two typical representative types of the Bangbu-type and the Langkazi-type. The Bangbu-type has the same oxygen isotope range(6‰-13‰) as that of orogenic gold deposit. However, the Langkazi-type shows same oxygen isotope range with the Original Magma Water(OMW). The ore-forming fluids hydrogen and oxygen isotopes of most deposits in Himalayan collisional belt fall among endmembers A, B and C, indicating that most of ore-forming fluids are not of a single fluid source, but have the characteristics of fluid mixing with multiple sources. |
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