Characteristics of fluid inclusions and their geological significance: A case study of the Jiling uranium deposit in Gansu Province
-
摘要:
为确定芨岭铀矿成矿流体的性质,对成矿期碳酸盐脉开展了详细的流体包裹体研究。包裹体岩相学和显微测温结果表明,碳酸盐脉主要发育气相包裹体、液相包裹体和纯液相包裹体;包裹体均一温度为141~295℃(峰值分别为170~180℃、240~250℃),盐度为2.09%~7.69% NaCleqv(峰值5%~6% NaCleqv),属于低-中温、低盐度铀矿床。激光拉曼和群体包裹体成分分析结果显示:成矿流体气相成分以CH4、H2为主,H2S、N2、CO2次之,液相成分富H2O和CH4,成矿流体属于NaCl-H2O±CH4±CO2体系。结合C、O同位素组成,δ13CVPDB值在-1.50‰~-6.33‰之间,δ18OSMOW值为-2.577‰~5.051‰,成矿热液的水源主要为岩浆热液与大气降水混合特征,且以大气降水形成为主。结合成矿流体特征,流体不混溶或沸腾作用导致相分离产生铀沉淀,以及流体脱气(CO2)作用导致铀矿质沉淀、富集,是芨岭铀成矿的主要成因。
Abstract:Detailed study of fluid inclusions in metallogenic period carbonate veins was conducted to reveal the ore-forming fluid features. Petrographic and microthermometric studies of fluid inclusions suggest that the main types of fluid inclusions of the Jiling uranium deposit are gaseous, liquid and pure liquid inclusions. Temperature test shows that the homogenization temperature and salinity of fluid inclusions vary from 141℃ to 295℃ (mostly in the ranges of 170~180℃ and 240~250℃) and 2.09%~7.69% NaCleqv (with the peak values varying in the range of 5%~6%Na Cleqv) respectively. Based on these results, the authors have reached the conclusion that the ore-forming fluids of the Jiling uranium deposit should be of low temperature and salinity. Laser Raman and group fluid inclusions content studies indicate that gas composition of the ore-forming fluids are mainly CH 4 and H2 with some H2S, N2, and CO2. The ore-forming fluids are then defined to be of the NaCl-H2O±CH4±CO2 system. The results show that δ13C values relative to the VPDB scale range from-1.50‰ to-6.33‰, and δ18O values fall between-2.577‰ and 5.051‰. The features of ore-forming fluids show that hydrothermal fluids are characterized by a mixture of magmatic fluids and atmospheric water, dominated by the latter. Further research suggests that the mineralized ∑CO2 mainly came from mantle degassing related to regional deep faults with minor contribution of marine carbonate rocks. It is concluded that uranium deposition in the Jiling area was related to the phase separation.
-
Key words:
- Jiling uranium deposit /
- fluid inclusion /
- geological significance /
- Gansu Province
-
-
图 1 甘肃省芨岭地区地质图(据参考文献[4]修改)
Figure 1.
表 1 芨岭铀矿碳酸盐脉流体包裹体显微测温数据及参数
Table 1. Microthermometric data and estimated parameters of fluid inclusions in carbonate from the Jiling uranium deposit
样号 测试数 均一相态 Ti/℃ Tht/℃ NaCleqv/% p1/MPa h1/km ρ/(g· m-3) ZKJ9-2-6 6 液相 -0.7~-1.8 172.0~187.6 1.2~3.1 7.6~22.8 0.3 ~0.8 0.81~0.91 5 气相 -2.2~-4.1 193.5~200.0 3.6~6.6 27.9~59.1 0.9 ~2.0 0.83~0.92 ZKJ9-2-7 5 液相 -2.5~-3.4 188.5~195.4 4.2~5.6 33.1~47.9 1.1 ~1.6 0.93~0.95 6 气相 -2.0~-2.4 165.2~180.6 3.4~4.0 25.7 ~31.6 0.9 ~1.1 0.85~0.93 ZKJ9-2-8 5 液相 -3.1~-3.5 171.7~173.4 5.1~5.7 43.1~49.5 1.4 ~1.6 0.87~0.95 6 气相 -1.7~-2.6 141.1~171.3 2.8~4.4 20.7 ~35.4 0.7~1.2 0.92~0.93 ZKJ9-2-9 4 液相 -4.0~-4.3 182.4~185.5 6.4~6.8 56.6~61.5 1.9~2.0 0.83~0.88 5 气相 -2.6~-3.4 168.8~174.2 4.3~5.6 34.6 ~47.9 1.2 ~1.6 0.93~0.97 ZKJ9-2-10 5 液相 -1.2~-1.7 195.4~214.0 2.1~2.9 14.6 ~21.4 0.5~0.7 0.92~0.95 5 气相 -3.2~-3.7 180.5~192.1 5.2~5.9 43.9~51.8 1.5 ~1.7 0.86~0.89 ZKJ9-2-11 4 液相 -2.1~-2.7 279.8~287.8 3.5~4.5 27.2 ~36.9 0.9 ~1.2 0.93~0.97 5 气相 -4.0~-4.6 245.0~246.8 6.4~7.3 57.4 ~67.9 1.9 ~2.3 0.85~0.93 ZKJ9-2-12 4 液相 -1.8~-2.0 291.2~294.5 3.0~3.3 22.1 ~25.0 0.7 ~0.8 0.92~1.07 4 气相 -4.6~-5.0 205.1~226.6 7.2~7.7 67.1~72.7 2.2~2.4 0.97~1.03 ZKJ9-2-13 4 液相 -1.7~-2.5 245.3~256.6 2.8~4.2 20.7 ~33.1 0.7~1.1 0.92~0.93 5 气相 -3.7~-4.5 217.3~223.4 6.0~7.0 52.6 ~64.7 1.8~2.2 0.94~0.97 注:Ti为冰点下降温度;Tht为均一温度;NaCl为盐度;p1为成矿压力;h1为成矿深度;ρ为密度 -
[1] 柴保民.龙首山花岗岩与铀矿化的关系[J].地质科研, 1987, 1/2:39-48. http://www.cnki.com.cn/Article/CJFDTOTAL-DZKT201506008.htm
[2] 胡能高.甘肃东大山地区龙首山岩群地球化学特征及其构造环境[J].长安大学学报, 2003, 25(4):32-39. http://www.cnki.com.cn/Article/CJFDTOTAL-XAGX200304008.htm
[3] 孙圭, 赵致和.中国北西部铀矿地质志 (下)[M].西安:核工业西北地质局, 1988:375-380.
[4] 陈云杰, 赵如意, 李涛.甘肃省铀边寺铀矿床铀化特征及成矿条件分析[J].甘肃地质, 2011, 20(3):46-50. http://www.cnki.com.cn/Article/CJFDTotal-GSDZ201103007.htm
[5] 陈云杰, 赵如意, 武彬.甘肃龙首山地区芨岭铀矿床隐爆角砾岩发现及成因探讨[J].地质与勘探, 2012, 48(6):1-8. http://www.cnki.com.cn/Article/CJFDTOTAL-DZKT201206007.htm
[6] 陈云杰, 傅成铭, 王刚, 等.花岗岩型热液铀矿床C、O同位素研究——以甘肃省龙首山芨岭矿区为例[J].地质与勘探, 2011, 50(4):641-648. http://www.cnki.com.cn/Article/CJFDTOTAL-DZKT201404004.htm
[7] 赵如意, 陈云杰, 武彬, 等.甘肃龙首山芨岭地区钠交代型铀矿成矿模式研究[J].地质与勘探, 2013, 49(1):67-74. http://www.cnki.com.cn/Article/CJFDTOTAL-DZKT201301009.htm
[8] 张朋, 杨宏智, 孙景贵, 等.黑龙江省马连金矿床流体包裹体特征及其地质意义[J].中国地质, 2015, 42(1):265-274. http://www.cnki.com.cn/Article/CJFDTOTAL-DIZI201501020.htm
[9] 周慧, 郗爱华, 熊益学, 等.流体包裹体的研究进展[J].矿物学报, 2013, 33(1):92-100. http://www.cnki.com.cn/Article/CJFDTOTAL-KYDH201401001.htm
[10] 卢焕章, 范宏瑞, 倪培, 等.流体包裹体[M].北京:科学技术出版社, 2004:1-487.
[11] 刘斌, 沈昆.流体包裹体热力学基础[M].北京:地质出版社, 1999:1-290.
[12] 孙晓明, 王敏, 薛婷, 等.流体包裹体中微量气体组成及其成矿示踪体系研究新进展[J].地学前缘, 2004, 11(2):471-478. http://www.cnki.com.cn/Article/CJFDTOTAL-DXQY200402024.htm
[13] 陈勇, 周瑶琪, 查明, 等. CH4-H2O体系流体包裹体拉曼光谱定量分析和计算方法[J].地质论评, 2007, 53(6):814-823. http://www.cnki.com.cn/Article/CJFDTotal-DZLP200706018.htm
[14] 王蕾.流体包裹体分析法在铀矿床研究中的应用——以相山铀矿田邹家山、沙洲矿床为例[J].铀矿地质, 2011, 27(6):331-336. http://www.cnki.com.cn/Article/CJFDTOTAL-YKDZ201106003.htm
[15] 苟学明, 李万华, 姬海军, 等.巴丹吉林盆地沙枣泉铀矿床成矿特征与成矿模式[J].铀矿地质, 2014, 30(1):7-13. http://www.cnki.com.cn/Article/CJFDTOTAL-YKDZ201401002.htm
[16] Vapnik Y, Moroz I. Compositions and formation conditions of flu-id inclusions in emerald from the Maria deposit[J]. Mineralogical Magazine, 2002, 66(1):201-213. doi: 10.1180/0026461026610023
[17] Bruke E A J. Raman micro-spectrometry of fluid inclusion[J]. Lith-os, 2001, 55(1/4):139-158. http://www.sciencedirect.com/science/article/pii/0375674291900653
[18] 卢焕章.地幔岩中流体包裹体研究[J].岩石学报, 2008, 24(9):1954-1960 http://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200809002.htm
[19] Potter R W Ⅱ, Clynne M A, Brown D L. Freezing pointdepres-sion of aqueous sodium chloride solutions[J]. Econ. Geol., 1978, 73:284-285. doi: 10.2113/gsecongeo.73.2.284
[20] Hall D L, Sterner S M, Bodnar R J. Freeing point depression of Na-Cl-KCl-H2O solutions[J]. Econ. Geol., 1988, 83:197-202. doi: 10.2113/gsecongeo.83.1.197
[21] 刘斌.中高盐度NaCl-H2O包裹体的密度式和等容式及其应用[J].地质论评, 2001, 47(6):617-622. http://www.cnki.com.cn/Article/CJFDTotal-DZLP200106014.htm
[22] 邵洁涟, 梅建明.浙江火山岩区金矿床的矿物包裹体标型特征研究及其成因找矿意义[J].矿物岩石, 1986, 6(3):103-111. http://www.cnki.com.cn/Article/CJFDTOTAL-KWYS198603012.htm
[23] 邵洁连.金矿找矿矿物学[M].武汉:中国地质大学出版社, 1999:1-150.
[24] 张德会, 周圣华, 万天丰, 等.矿床形成深度与深部成矿预测[J].地质通报, 2007, 26(12):1509-1518. doi: 10.3969/j.issn.1671-2552.2007.12.002 http://dzhtb.cgs.cn/ch/reader/view_abstract.aspx?flag=1&file_no=20071201&journal_id=gbc
-