Geological Characteristics and Ore-forming Fluids of the Dahu Au-Mo Deposit in Xiaoqinling Gold Field

doi:10.19657/j.geoscience.1000-8527.2021.116

Abstract

Abstract:

The Xiaoqinling district, located on the southern margin of the North China Craton, is the second largest gold province in China.The Dahu is a typical Au-Mo deposit on the northern margin of the Xiaoqinling terrane, and is hosted by migmatitic granites and biotite-plagioclase gneiss of the Taihua supergroup metamorphic complex.According to crosscutting relationships and mineral assemblages, the hydrothermal ore-forming process can be divided into four stages, including quartz-K-feldspar-molybdenite assemblage(Ⅰ), quartz-pyrite-molybdenite assemblage(Ⅱ), quartz-pyrite-polymetallic sulfide assemblage(Ⅲ), and quartz-calcite assemblage(Ⅳ).Petrographic, fluid inclusion microthermometric and micro-Raman spectroscopic analyses reveal three types of fluid inclusions in quartz, i.e., CO₂-H₂O (C-type), H₂O-solution (W-type), and pure CO₂(PC-type). Stage Ⅰ quartz mainly contains C-type, PC-type, and W-type inclusions.Homogenization temperatures of C-type inclusions vary from 275.3 to 350.0 ℃ with salinity of 6.3% to 14.7%, and have δ¹⁸O_water values from 4.6‰ to 5.9‰ and δD values from -82‰ to -63‰.Stage Ⅱ quartz mainly contains C-type inclusions with small amounts of PC-type and W-type inclusions.Their C-type inclusions homogenized at 260.0 to 312.7 ℃, lower than that of stage Ⅰ.The fluid salinities vary from 2.2% to 17.5%.The fluids have δ¹⁸O_water values from 3.0‰ to 4.5‰ and δD values from -90‰ to -50‰.Maximum trapping pressure estimated from the CO₂-H₂O inclusions are 196 MPa for stage Ⅱ, corresponding to 7.1 km depth.The ore-forming fluid is characterized by meso- to hypothermal, CO₂-rich and low salinity, resembling typical metamorphic fluids.Hydrogen-oxygen isotope signatures indicate that the fluids were originated from metamorphic devolatilization.The reactions of metamorphic fluid with the wallrocks may have led to the isotope exchange.Therefore, the Dahu Au-Mo deposit is best classified to be an orogenic-type gold deposit.

Key words: Xiaoqinling district, Dahu Au-Mo deposit, fluid inclusion, H-O isotope, orogenic gold deposit

CLC Number:

P618.51

GUO Yuncheng, LIU Jiajun, YIN Chao, GUO Mengxu. Geological Characteristics and Ore-forming Fluids of the Dahu Au-Mo Deposit in Xiaoqinling Gold Field[J]. Geoscience, 2021, 35(06): 1536-1550.

Figures/Tables 14

Fig.1 Geologic map of the Xiaoqinling gold field (modified after Chen[16])

Fig.2 Geologic map of the Dahu Au-Mo deposit and sketch map of the sampling locations (modified from Sun et al.[4])

Fig.3 Profile of No.0 Exploration Line in the Dahu Au-Mo deposit, and sketch map of the sampling locations (modified from Sun et al.[4])

Fig.4 Characteristics of ore hand-specimen from the Dahu Au-Mo deposit

Fig.5 Characteristics of mineral compositions from the Dahu Au-Mo deposit

Fig.6 Characteristics of mineral texture and wallrock alteration in the Dahu Au-Mo deposit

Table 1 Characteristics of fluid inclusions samples for microthermometric analysis from the Dahu Au-Mo deposit

样品号	成矿阶段	采样位置	样品特征描述
16DH-49	Ⅰ	F35矿脉矿石堆	乳白色石英脉,少量辉钼矿和黄铁矿
16DH-53	Ⅰ	F35矿脉蚀变围岩	钾长石化石英脉,可见少量辉钼矿和黄铁矿
16DH-61	Ⅰ	F5矿脉地表矿石堆	钾长石化石英脉,可见少量辉钼矿和黄铁矿
16DH-26	Ⅱ	F5矿脉330 m标高	烟灰色石英脉,沿裂隙发育辉钼矿
16DH-56	Ⅱ	F5矿脉400 m标高	烟灰色石英脉,自形黄铁矿呈脉状发育
16DH-57	Ⅱ	F5矿脉400 m标高	烟灰色石英脉,自形黄铁矿呈脉状发育
16DH-58	Ⅱ	F5矿脉400 m标高	烟灰色石英脉,自形黄铁矿呈脉状发育
16DH-65	Ⅱ	F5矿脉地表矿石堆	蔷薇粉色石英脉,少量黄铁矿
16DH-72	Ⅱ	F5矿脉地表矿石堆	宽20~30 cm石英脉,自形黄铁矿呈脉状发育
16DH-37	Ⅲ	F5矿脉295 m标高	烟灰色石英脉,方铅矿和黄铁矿呈脉状发育
16DH-40	Ⅲ	F7矿脉280 m标高	宽10~30 cm石英脉,网脉状方铅矿和黄铁矿

Fig.7 Micrographs of typical fluid inclusions in quartz from the Dahu Au-Mo deposit

Fig.8 Laser Raman spectroscopy of fluid inclusion composition analysis for the Dahu Au-Mo deposit

Table 2 Microthermometric data of fluid inclusions for the Dahu Au-Mo deposit

成矿阶段	类型		$T m, C O 2$ /℃	T_m,cla/℃	$T h, C O 2$ /℃	T_m,ice/℃	T_h,tot/℃
Ⅰ阶段	C型	25	-64.7~-56.6	-1.5~7.8	8.3~31.1		275.3~350.0
Ⅱ阶段	C型	49	-64.5~-56.6	-2.2~8.9	11.0~29.5		260.0~312.7
	PC型	1	-58.6		14.3
	W型	8				-9.5~-6.0	228.9~260.0
Ⅲ阶段	C型	16	-61.8~-56.6	3.5~8.9	13.7~29.2		245.3~287.6
Ⅲ阶段	PC型	2	-60.8		13.7~15.0
Ⅳ阶段	W型	14				-11.6~-8.5	200.0~251.0

Table 2 Microthermometric data of fluid inclusions for the Dahu Au-Mo deposit

成矿阶段	类型		$T m, C O 2$ /℃	T_m,cla/℃	$T h, C O 2$ /℃	T_m,ice/℃	T_h,tot/℃
Ⅰ阶段	C型	25	-64.7~-56.6	-1.5~7.8	8.3~31.1		275.3~350.0
Ⅱ阶段	C型	49	-64.5~-56.6	-2.2~8.9	11.0~29.5		260.0~312.7
	PC型	1	-58.6		14.3
	W型	8				-9.5~-6.0	228.9~260.0
Ⅲ阶段	C型	16	-61.8~-56.6	3.5~8.9	13.7~29.2		245.3~287.6
Ⅲ阶段	PC型	2	-60.8		13.7~15.0
Ⅳ阶段	W型	14				-11.6~-8.5	200.0~251.0

Table 3 Statistics of ore-fluid salinity and pressure estimation for the Dahu Au-Mo deposit

成矿阶段	类型	盐度/%		估算压力/ MPa	流体密度/ (g/cm³)	估算深度/km
成矿阶段	类型	范围	平均值	估算压力/ MPa	流体密度/ (g/cm³)	估算深度/km
Ⅰ阶段	C型	4.3~16.9	11.2	82.9~186.3	0.831~0.999	3.0~6.8
Ⅱ阶段	C型	2.2~17.5	9.5	63.6~196.3	0.777~0.978	3.1~7.1
Ⅱ阶段	W型	9.2~13.2	11.6	63.5~71.8	0.920~1.108	2.4~2.6
Ⅲ阶段	C型	2.2~11.3	8.2	105.0~172.0	0.820~0.952	3.8~6.3
Ⅲ阶段	PC型	6.6~9.3	8.6
Ⅳ阶段	W型	9.2~15.6	12.0	55.6~71.8	0.92~1.01	1.8~2.5

Table 4 Hydrogen and oxygen isotope compositions of quartz from the Dahu Au-Mo deposit

样品编号	测试矿物	均一温度/℃	δ¹⁸O_石英 /‰	δ¹⁸O_水 /‰	δD/‰	成矿阶段
16DH-38	石英	313.9	12.3	5.9	-82	Ⅰ
16DH-60	石英	313.9	11.0	4.6	-63	Ⅰ
16DH-20	石英	289.3	11.9	4.6	-90	Ⅱ
16DH-6	石英	289.3	11.7	4.4	-75	Ⅱ
16DH-57	石英	289.3	11.8	4.5	-50	Ⅱ
16DH-58	石英	289.3	10.9	4.3	-59	Ⅱ
16DH-72	石英	289.3	10.7	3.6	-44	Ⅱ
16DH-43	石英	258.3	11.5	2.9	-77	Ⅲ
16DH-40	石英	258.3	11.6	2.1	-73	Ⅲ
16DH-62	石英	258.3	12.2	3.6	-72	Ⅲ
16DH-35	石英	258.3	11.3	2.7	-77	Ⅲ

Fig.9 δ18Owater vs.δDSMOW plot for the ore-forming fluid of the Dahu Au-Mo deposit (modified from Taylor[32])

Fig.10 Evolution histograms of homogenization temperature and salinity of fluid inclusions from the Dahu Au-Mo deposit

References 45

[1]	陈衍景, 富士谷. 豫西金矿成矿规律[M]. 北京: 地震出版社, 1992:1-234.
[2]	MAO J W, GOLDFARB R J, ZHANG Z W, et al. Gold deposits in the Xiaoqinling-Xiong'ershan region, Qinling Mountains, central China[J]. Mineralium Deposita, 2002, 37:306-325. DOI URL
[3]	MAO J W, XIE G Q, BIERLEIN F, et al. Tectonic implications from Re-Os dating of Mesozoic molybdenum deposits in the East Qinling-Dabie orogenic belt[J]. Geochimica et Cosmochimica Acta, 2008, 72(18):4607-4626. DOI URL
[4]	孙卫志, 王振强. 小秦岭大湖矿区钼、金矿体地质、地球化学特征与差异性分析[J]. 地质论评, 2012, 58(4):671-680.
[5]	CHANG M, LIU J J, CARRANZA E J M, et al. Newly discovered scheelite in quartz vein-type gold deposits,Xiaoqinlinggold district,and its geological significance[J]. Acta Geologica Sinic, 2020, 94(4):1305-1307.
[6]	陈莉. 小秦岭大湖金矿床成矿流体特征及矿床成因探讨[D]. 北京: 中国地质大学 (北京), 2006.
[7]	李厚民, 叶会寿, 毛景文, 等. 小秦岭金(钼)矿床辉钼矿铼-锇定年及其地质意义[J]. 矿床地质, 2007, 26(4):417-424.
[8]	李诺, 孙亚莉, 李晶, 等. 小秦岭大湖金钼矿床辉钼矿铼-锇同位素年龄及印支期成矿事件[J]. 岩石学报, 2008, 24(4):810-816.
[9]	蒋少涌, 戴宝章, 姜耀辉, 等. 胶东和小秦岭: 两类不同构造环境中的造山型金矿省[J]. 岩石学报, 2009, 25(11):2727-2738.
[10]	简伟. 河南小秦岭大湖金钼矿床地质特征、成矿流体及矿床成因研究[D]. 北京: 中国地质大学(北京), 2010.
[11]	赵海香. 河南小秦岭金矿成矿作用地球化学研究[D]. 南京:南京大学, 2011.
[12]	孙保花, 牛树银, 王杏村, 等. 小秦岭大湖金矿矿体原生晕特征研究[J]. 黄金科学技术, 2014, 22(4):55-60.
[13]	JIAN W, LEHMANN B, MAO J W, et al. Mineralogy, fluid characteristics, and Re-Os age of the late Triassic Dahu Au-Mo deposit, Xiaoqinling region, central China: evidence for a magmatic-hydrothermal origin[J]. Economic Geology, 2015, 100:119-145.
[14]	YIN Chao, LIU Jiajun, ZHAI Degao, et al. New discovery of Telluride and Bi-Sulfosalt in the Dahu quartz vein-style Au-Mo deposit, Xiaoqinling region, China[J]. Acta Geologica Sinica, 2019, 93(1):241-243.
[15]	YIN Chao, LIU Jiajun, CARRANZA E J M, et al. Mineralogical constraints on the genesis of the Dahu quartz vein-style Au-Mo deposit, Xiaoqinling gold district, China: Implications for phase relationships and physicochemical conditions[J]. Ore Geology Reviews, 2019, 113:103107. DOI URL
[16]	陈衍景. 造山型矿床、成矿模式及找矿潜力[J]. 中国地质, 2006, 33(6):1181-1196.
[17]	倪志耀, 王仁民, 童英, 等. 河南洛宁太华岩群斜长角闪岩的锆石²⁰⁷Pb/²⁰⁶Pb和角闪石⁴⁰Ar/³⁹Ar年龄[J]. 地质论评, 2003, 49(4):361-366.
[18]	张宗清, 黎世美. 河南省西部熊耳山地区太古宙太华群变质岩的Sm-Nd, Rb-Sr年龄及其地质意义[M]//程裕淇.华北地台早寒武纪地质研究文集. 北京: 地质出版社, 1998:123-132.
[19]	李厚民, 陈毓川, 王登红, 等. 小秦岭变质岩及脉体锆石SHRIMP U-Pb年龄及其地质意义[J]. 岩石学报, 2007, 23(10):2504-2512.
[20]	张国伟, 孟庆任, 于在平, 等. 秦岭造山带的造山过程及其动力学特征[J]. 中国科学(D辑:地球科学), 1996, 26(3):193-200.
[21]	AMES L, TILTON G R, ZHOU G Z. Timing of collision of the Sino-Korean and Yangtse cratons: U-Pb zircon dating of coesite-bearing eclogites[J]. Geology, 1993, 21(4):339-342. DOI URL
[22]	张进江, 郑亚东, 刘树文. 小秦岭变质核杂岩的构造特征、形成机制及构造演化[M]. 北京: 海洋出版社, 1998:1-120.
[23]	毛景文, 谢桂青, 张作衡, 等. 中国北方中生代大规模成矿作用的期次及其地球动力学背景[J]. 岩石学报, 2005, 21(1):169-188.
[24]	赵海香, 戴宝章, 李斌, 等. 小秦岭车仓峪钼矿成因研究:辉钼矿Re-Os年龄及黄铁矿微量元素制约[J]. 岩石学报, 2015, 31(3):784-790.
[25]	杨志民. 河南省灵宝市大湖矿区金矿深部勘探地质报告[R]. 洛阳:河南省地质矿产勘查开发局第一地质调查队, 1995:27-47.
[26]	LI N, CHEN Y J, FLETCHER I R, et al. Triassic mineralization with Cretaceous overprint in the Dahu Au-Mo deposit,Xiaoqinling gold Province: Constraints from SHRIMP monazite U-Th-Pb geochronology[J]. Gondwana Research, 2011, 20:543-552. DOI URL
[27]	简伟 .你好, 灵宝矿![J]. 国土资源科普与文化, 2020(1):16-19.
[28]	BROWN P E. Data handling and fluid inclusions[M]//中国科学院广州地球化学研究所及成矿动力学重点实验室,中国科学院地球化学研究所及矿床地球化学国家重点实验室,广东省地质学会等.地质流体和流体包裹体研究国际学术会议暨第十五届全国流体包裹体会议论文集.广州:中国科学院广州地球化学研究所, 2007:1-6.
[29]	李洪伟, 冯连君, 陈健, 等. 密封石英管法快速分析包裹体中氢同位素[J]. 质谱学报, 2015, 36(1):40-44.
[30]	CLAYTON R N, O'NEIL J R, MAYEDA T K. Oxygen isotope exchange between quartz and water[J]. Journal of Geophysical Research, 1972, 77(17) : 3057-3067. DOI URL
[31]	GOLDFARB R J, BAKER T, DUBE B, et al. Distribution, character, and genesis of gold deposits in metamorphic terranes[M]//SEG.Economic Geology 100th Anniversary Volume. Littleton: Society of Economic Geologists, 2005:407-450.
[32]	TAYLOR H P. The application of oxygen and hydrogen isotope studies to problem of hydrothermal alteration and ore deposition[J]. Economic Geology, 1974, 69:843-883. DOI URL
[33]	何春芬. 小秦岭金矿田北矿带F₅断裂控矿作用[J]. 黄金, 2003, 24(9):3-7.
[34]	张元厚, 李宗彦, 张孝民, 等. 小秦岭金(钼)矿田北矿带推覆构造演化与成矿作用[J]. 吉林大学学报(地球科学版), 2009, 39(2):244-254.
[35]	高凯. 小秦岭金矿田北矿带金矿床中深部控矿构造及围岩蚀变研究[D]. 北京: 中国地质大学(北京), 2015.
[36]	王义天, 毛景文, 卢欣祥, 等. 河南小秦岭金矿区Q875脉中深部矿化蚀变岩的⁴⁰Ar-³⁹Ar年龄及其意义[J]. 科学通报, 2002, 47(18):1427-1431.
[37]	黎世美, 瞿伦全, 苏振邦, 等. 小秦岭金矿地质和成矿预测[M]. 北京: 地质出版社, 1996:1-250.
[38]	FAN H R, XIE Y H, ZHAO R, et al. Dual origins of Xiaoqinling gold-bearing quartz veins: Fluid inclusion evidence[J]. Chinese Science Bulletin, 2000, 45(15):1424-1430. DOI URL
[39]	LI Q Z, CHEN Y J, ZHONG Z Q, et al. Ar-Ar dating on the metallogenesis of the Dongchuang gold deposit in the Xiaoqinling area[J]. Acta Geologica Sinica, 2002, 76(4):488-493. DOI URL
[40]	陈衍景, 倪培, 范宏瑞, 等. 不同类型热液金矿床的流体包裹体特征[J]. 岩石学报, 2007, 23(9):2085-2108.
[41]	栾世伟, 陈尚迪. 小秦岭金矿主要控矿因素及成矿模式[J]. 地质找矿论丛, 1990, 5(4):1-14.
[42]	GOLDFARB R J, PHILLIPS G N, NOKLEBERG W J. Tectonic setting of synorogenic gold deposits of the Pacific Rim[J]. Ore Geology Reviews, 1998, 13(1/2/3/4/5):185-218. DOI URL
[43]	陈衍景, 翟明国, 蒋少涌. 华北大陆边缘造山过程与成矿研究的重要进展和问题[J]. 岩石学报, 2009, 25(11):2695-2726.
[44]	GROVES D I. The crustal continuum model for late-Archaean lode-gold deposits of the Yilgarn Block, Western Australia[J]. Mineralium Deposita, 1993, 28:366-374. DOI URL
[45]	GROVES D I, GOLDFARB R J, GEBRE-MARIAM M, et al. Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types[J]. Ore Geology Reviews, 1998, 13:7-27. DOI URL