Fluid inclusion characteristics and ore genesis of the Banduo Pb-Zn deposit in Songduo area, southern Tibet
-
摘要:
藏南松多地区板多铅锌矿床位于冈底斯成矿带东段,矿床产于松多岩组、花岗闪长岩与隐伏似斑状花岗岩的接触带及其附近,迄今共圈定3个矿体,矿体呈脉状、透镜状,受北东向断裂控制。矿石中主要金属矿物为方铅矿、闪锌矿与黄铜矿,其次为毒砂、黄铁矿、磁黄铁矿等; 非金属矿物以石英、绢云母为主,其次为白云母与方解石。矿床可划分为3个成矿阶段:Ⅰ.石英-毒砂-黄铁矿-磁黄铁矿阶段; Ⅱ.石英-黄铁矿-闪锌矿-黄铜矿-方铅矿阶段; Ⅲ.石英-方解石阶段。其中,第Ⅱ阶段为主成矿阶段。为查明成矿物理化学条件和成矿流体特征,选取主要成矿阶段的石英开展流体包裹体岩相学和显微测温研究。结果表明,石英主要发育气液两相包裹体,并含有少量纯液相与纯气相包裹体; 成矿流体属中温、低盐度、低密度的NaCl-H2O体系; 成矿早期存在沸腾现象,之后,流体的减压降温应是铅锌富集成矿的主要因素。综合成矿地质条件、矿床地质特征及流体包裹体研究,初步认为,板多铅锌矿属中温热液脉型铅锌矿床。
-
关键词:
- 流体包裹体 /
- 矿床成因 /
- 中温热液脉型铅锌矿床 /
- 板多矿床 /
- 松多地区
Abstract:The Banduo Pb-Zn deposit in Songduo area of southern Tibet is located along east Gangdise metallogenic belt. Three orebodies have been delineated so far, which are veined and lentoid in form and are controlled by NE-trending faults. The major metallic minerals are galena, sphalerite and chalcopyrite, together with some other metallic minerals such as arsenopyrite, pyrite and pyrrhotite. The major nonmetallic minerals are quartz and sericite, and other nonmetallic minerals are muscovite and calcite.The deposit can be divided into three metallogenic stages:Ⅰ. quartz-arsenopyrite-pyrite-pyrrhotite stage; Ⅱ. quartz-pyrite-sphalerite-chalcopyrite-galena stage; Ⅲ. quartz-calcite stage, with the major metallogenic stage being the second stage. In order to determine the ore-forming physical and chemical conditions and characteristics of ore-forming fluids, the authors selected the quartz grains formed at the major metallogenic stage to study the petrography and micro-thermometry of fluid inclusions. The results show that fluid inclusions in quartz are mainly composed of vapor-liquid two-phase inclusions, with a small amount of pure gas and pure liquid inclusions. The main ore-forming fluid is NaCl-H2O characterized by medium temperature(163.5~344.5℃, 266.3℃average), low salinity(0.70%~7.15%NaCl eqv, 3.39% NaCl eqv averagely) and low density (0.65~0.95g/cm3, 0.79g/cm3 averagely). The fluid inclusion study indicates that boiling occurred at the early stage of mineralization, then decrease of temperature and pressure of the fluids should be the main factor for Pb and Zn concentration and mineralization. Based on comprehensive ore-formation geological conditions, geological characteristics of the deposit, and fluid inclusions studies, the authors tentatively hold that the deposit is a mesothermal vein type Pb-Zn deposit.
-
Key words:
- fluid inclusion /
- ore genesis /
- mesothermal vein type Pb-Zn deposit /
- Banduo deposit /
- Songduo area
-
图 2 板多铅锌矿床矿区地质图(据参考文献[3]修改)
Figure 2.
表 1 板多铅锌矿成矿阶段划分
Table 1. Mineralization stages of the Banduo Pb-Zn deposit
矿物 Ⅰ.石英-毒砂-黄铁矿-磁黄铁矿阶段 Ⅱ.石英-黄铁矿-闪锌矿-黄铜矿-方铅矿阶段 Ⅲ.石英-方解石阶段 石英 毒砂 黄铁矿 磁黄铁矿 闪锌矿 黄铜矿 方铅矿 方解石 表 2 板多铅锌矿主要成矿元素含量
Table 2. The content of major ore elements of the Banduo Pb-Zn deposit
10-6 编号 检测项目 Ag As Cd Cu Fe Mo Pb S Sb Sr V Zn Au 检出限 1 50 10 10 0.05 10 20 0.05 50 10 10 20 0.005 1 P1010g2 30 90 130 1120 4.9 1800 6.31 150 15400 0.066 2 P1010g3 22 100 280 570 10.6 10 3890 >10.0 10 120 39900 0.014 3 P1017g7 11 290 110 550 5.8 10 8610 7.41 10 70 22600 0.141 4 P1017g8 20 880 30 310 14.8 130 22100 >10.0 10 60 5860 0.31 5 P1017g9 8 630 60 450 11.15 340 3230 >10.0 90 70 12500 1.54 6 P1023g1 76 740 240 1140 10.4 60 95500 >10.0 180 10 61100 0.096 7 P1023g3 5 1150 10 190 11.25 70 1850 >10.0 70 10 10 1660 0.129 8 P1023g4 40 280 180 1230 9.85 10 57400 >10.0 240 10 44800 0.058 9 P1023g5 46 1110 20 400 21.4 230 45900 >10.0 70 10 10 4040 0.219 10 P1023g6 34 380 230 1100 14.8 10 49100 >10.0 80 10 59000 0.11 11 P1028g2 25 440 200 900 18.8 10 43800 >10.0 50 10 10 48700 0.081 12 P1028g4 18 200 90 550 6.19 30 26000 8.47 50 70 20400 0.067 13 P1028g5 5 910 140 270 8.16 10 6020 9.74 160 30 35600 0.048 14 P1028g6 13 1650 40 420 6.81 20700 8.26 70 170 50 10600 0.116 15 P1037g2 45 3590 2340 45.8 530 >10.0 10 180 0.117 16 P1037g3 48 94100 130 1600 9.42 9150 7.75 100 30 22200 0.913 17 P1037g4 684 >100000 240 8250 15.25 35.35% >10.0 680 10 51600 1.325 18 P1037g5 452 58000 600 7230 15.1 27.03% >10.0 430 10 12.78% 0.646 19 P1037g6 148 6670 150 850 16.55 80 15.96% >10.0 260 40 10 32200 0.286 20 P1037g7 118 2150 690 3490 46.2 19850 >10.0 50 12.79% 3.7 注:百分数为高于检出上限后进行高含量滴定所得数据,空白为低于检出限数据 表 3 板多铅锌矿床包裹体均一温度和盐度测定结果及流体数据
Table 3. Microthermometric and salinity data of fluid inclusions and fluid data from Banduo Pb-Zn deposit
成矿阶段 包裹体数 均一温度/℃ 冰点/℃ 盐度/%NaCl eqv 密度/(g·cm-3) 压力/MPa 深度/km 范围 均值 范围 均值 范围 均值 范围 均值 范围 均值 范围 均值 第Ⅰ阶段 37 193.3~359.4 308.4 0.7~-3.7 2.1 1.22~5.99 3.59 0.65~0.90 0.72 51.2~96.2 80.1 1.71 ~3.21 2.67 第Ⅱ阶段 58 163.5~344.5 266.3 0.4~-4.5 2.0 0.70~7.15 3.39 0.65~0.95 0.79 34.5~92.4 68.6 1.15~3.08 2.29 第Ⅲ阶段 38 146.3~359.8 209.9 -0.3~-3.2 -1.5 0.53~5.32 2.52 0.62~0.94 0.87 34.1~94.4 51.4 1.13~3.15 1.71 -
[1] 西藏自治区地质矿产局.西藏自治区区域地质志[M].北京:地质出版社, 1993.
[2] 高忠维, 解超明, 任云生, 等.藏南色如朗金红石矿床地质特征及控矿条件[J].地质通报, 2017, 36(11):2181-2187. http://dzhtb.cgs.cn/ch/reader/view_abstract.aspx?file_no=20171119&flag=1
[3] 刘大明, 刘仪中, 袁诗魁.西藏工布江达县板多铅锌矿地质特征及成矿规律[J].四川地质学报, 2017, (2):218-222. doi: 10.3969/j.issn.1006-0995.2017.02.010
[4] 卢焕章, 范宏瑞, 倪培, 等.流体包裹体[M].北京:地质出版社, 2004.
[5] Potter R W I, Clynne M, Brown D L. Freezing point depression of aqueous sodium chloride solution[J]. Economic Geology, 1978, 73:284-285. doi: 10.2113/gsecongeo.73.2.284
[6] Bodnar R J. Revised equation and table for determining the freezing point depression of H2O-NaCl solutions[J]. Geochimica et Cosmochimica Acta, 1993, 57(3):683-684. doi: 10.1016/0016-7037(93)90378-A
[7] 刘斌, 段光贤. NaCl-H2O溶液包裹体密度式和等容式及其应用[J].矿物学报, 1987, 7(4):345-352. doi: 10.3321/j.issn:1000-4734.1987.04.010
[8] 刘斌, 沈昆.流体包裹体热力学[M].北京:地质出版社, 1999.
[9] 刘斌.利用流体包裹体及其主矿物共生平衡的热力学方程计算形成温度和压力[J].中国科学(B辑), 1987, (3):81-88. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000001580717
[10] 邵洁涟.金矿找矿矿物学[M].武汉:中国地质大学出版社, 1990.
[11] 孙振明, 任云生, 李才, 等.西藏班-怒带西段荣那铜(金)矿床流体包裹体特征及矿床成因[J].地质学报, 2015, 89(3):608-617. http://d.old.wanfangdata.com.cn/Periodical/dizhixb201503013
[12] 尹远, 梁维, 谢锦程, 等.藏南吉松铅锌矿流体包裹体特征及其地质意义[J].现代地质, 2015, 29(3):553-562. doi: 10.3969/j.issn.1000-8527.2015.03.007
[13] 费光春, 温春齐, 周雄, 等.西藏洞中拉铅锌矿床成矿流体研究[J].地质与勘探, 2010, 46(4):576-582. http://d.old.wanfangdata.com.cn/Periodical/dzykt201004002
[14] 邹公明, 李世金, 李良, 等.青海省沱沱河地区楚多曲铅锌矿床流体包裹体特征及矿床成因探讨[J].西北地质, 2014, 47(4):256-263. doi: 10.3969/j.issn.1009-6248.2014.04.027
[15] 王方国, 李光明, 林方成.西藏冈底斯地区矽卡岩型矿床资源潜力初析[J].地质通报, 2005, 24(4):378-385. doi: 10.3969/j.issn.1671-2552.2005.04.014 http://dzhtb.cgs.cn/ch/reader/view_abstract.aspx?file_no=20050474&flag=1
[16] 张德会.流体的沸腾和混合在热液成矿中的意义[J].地球科学进展, 1997, 12(6):546-552. http://d.old.wanfangdata.com.cn/NSTLQK/10.1109-MCG.2010.44/
[17] 魏振声.对矿物沸腾包裹体若干问题的探讨[J].国土资源导刊, 1989, (1):60-65. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000001430937
[18] 芮宗瑶, 李荫清, 王龙生, 等.从流体包裹体研究探讨金属矿床成矿条件[J].矿床地质, 2003, 22(1):13-23. doi: 10.3969/j.issn.0258-7106.2003.01.002
① 福建省地质调查研究院. 西藏自治区松多地区 1∶5万 3幅地质矿产调查报告. 2011.
② 青海省地质矿产局区调综合地质大队. 1∶20万下巴淌(沃卡)幅区域地质调查报告(矿产部分).1994.