Geological Characteristics and Ore-forming Fluids of the Jinlu Gold Deposit in Aohan Banner, Inner Mongolia

doi:10.19657/j.geoscience.1000-8527.2019.01.13

Abstract

Abstract:

The Jinlu gold deposit is located in the convergence of North China Craton and central Asian orogenic belt. Its ore-bodies controlled by the NE trending ductile-brittle faults, are hosted in metamorphic rocks of the Archean Xiaotazigou Formation and Triassic gneissic monzonitic granite. Based on the studies of fluid inclusions and electron probe, the aim of this paper is to discuss the characteristics and evolution of ore-forming fluids and to provide an insight into the ore genesis. The ore-forming process can be divided into four metallogenic stages, respectively named the white quartz stage(Ⅰ), the quartz-pyrite stage(Ⅱ), the quartz-polymetallic sulfide stage(Ⅲ) and carbonate stage(Ⅳ). Native gold with very high fineness are mainly produced in the Ⅲ-stage quartz and pyrite in the form of intergranular gold, fissured gold and inclusion gold. Petrographic observation indicates that fluid inclusions of the deposit can be divided into three types, i.e., aqueous inclusions, CO₂-bearing aqueous inclusions and daughter mineral-bearing multiphase inclusions. The Ⅰ-stage quartz mainly contains aqueous inclusions and CO₂-bearing aqueous inclusions. The homogenization temperatures, salinities and densities are in the ranges of 365 ℃ to 405 ℃, 7.9% to 11.7% and 0.61 g/cm³ to 0.70 g/cm³. All three types of inclusions are trapped in the Ⅱ-stage quartz. The homogenization temperatures, salinities and densities vary from 335 ℃ to 390 ℃, 4.3% to 35.5% and 0.62 g/cm ³ to 0.79 g/cm³. All three types of inclusions are found in the Ⅲ-stage quartz. The homogenization temperatures, salinities and densities have a range of 270 ℃ to 367 ℃, 1.7% to 37.8% and 0.64 g/cm ³ to 1.1 g/cm³. The studies of fluid inclusions in three metallogenic stages indicate that the ore-forming fluids belong to H₂O-NaCl-CO₂ system. The metallogenetic temperatures and fluid salinities gradually decreased and the densities showed a slightly increasing trend. Based on fluid inclusions and geologic characteristics, it is suggested that fluid boiling and sulfofication may be the main mechanism for the gold precipitation and enrichment in this deposit. The genesis of the Jinlu gold deposit is a magmatic hydrothermal gold deposit.

Key words: fluid inclusion, fluid boiling, Jinlu gold deposit, North China Craton, Inner Mongolia

CLC Number:

P618.51

GAO Liye, ZHANG Yongmei, GU Xuexiang, LIU Li, WANG Luzhi, OUYANG Xin. Geological Characteristics and Ore-forming Fluids of the Jinlu Gold Deposit in Aohan Banner, Inner Mongolia[J]. Geoscience, 2019, 33(01): 137-151.

Figures/Tables 12

References 36

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赋存状态	Au	Ag	Fe	Te	Ge	Cu	Sb	Co	Bi	Zn	S	总量	成色
裂隙金	94.03	3.57	0.57	0.06	—	—	0.05	—	0.68	—	0.12	99.1	963
	90.17	9.16	0.09	—	—	—	0.10	—	0.69	—	0.11	100.3	908
	88.67	9.10	—	0.08	—	—	—	—	0.62	0.15	0.07	98.7	907
	83.64	14.27	0.77	—	—	—	0.09	—	0.76	—	0.22	99.8	854
	77.78	19.19	1.02	0.12	0.05	—	0.06	—	0.37	—	0.27	98.9	802
粒间金	90.42	7.00	0.96	0.13	—	—	—	0.10	0.82	—	0.16	99.6	928
	89.09	9.43	0.70	0.26	—	0.10	0.12	—	0.83	—	0.25	100.8	904
	88.58	9.69	0.33	0.09	—	0.12	—	—	0.82	—	0.18	99.8	901
黄铁矿包体金	91.54	3.96	2.25	0.13	—	—	—	—	1.01	—	0.16	99.1	959
	80.93	16.58	1.22	0.17	0.03	—	—	—	0.71	—	0.25	100.0	830
	87.84	9.83	1.20	0.07	0.05	—	—	0.13	0.67	—	0.58	100.4	899
石英包体金	87.45	7.89	2.25	0.14	—	—	—	—	0.66	—	0.46	98.9	917
石英包体金	90.29	9.53	0.15	0.09	—	—	—	0.10	0.58	—	0.08	100.8	905
银金矿	56.22	41.17	0.46	0.13	0.05	—	—	—	0.42	0.19	0.17	98.8	577

赋存状态	Au	Ag	Fe	Te	Ge	Cu	Sb	Co	Bi	Zn	S	总量	成色
裂隙金	94.03	3.57	0.57	0.06	—	—	0.05	—	0.68	—	0.12	99.1	963
	90.17	9.16	0.09	—	—	—	0.10	—	0.69	—	0.11	100.3	908
	88.67	9.10	—	0.08	—	—	—	—	0.62	0.15	0.07	98.7	907
	83.64	14.27	0.77	—	—	—	0.09	—	0.76	—	0.22	99.8	854
	77.78	19.19	1.02	0.12	0.05	—	0.06	—	0.37	—	0.27	98.9	802
粒间金	90.42	7.00	0.96	0.13	—	—	—	0.10	0.82	—	0.16	99.6	928
	89.09	9.43	0.70	0.26	—	0.10	0.12	—	0.83	—	0.25	100.8	904
	88.58	9.69	0.33	0.09	—	0.12	—	—	0.82	—	0.18	99.8	901
黄铁矿包体金	91.54	3.96	2.25	0.13	—	—	—	—	1.01	—	0.16	99.1	959
	80.93	16.58	1.22	0.17	0.03	—	—	—	0.71	—	0.25	100.0	830
	87.84	9.83	1.20	0.07	0.05	—	—	0.13	0.67	—	0.58	100.4	899
石英包体金	87.45	7.89	2.25	0.14	—	—	—	—	0.66	—	0.46	98.9	917
石英包体金	90.29	9.53	0.15	0.09	—	—	—	0.10	0.58	—	0.08	100.8	905
银金矿	56.22	41.17	0.46	0.13	0.05	—	—	—	0.42	0.19	0.17	98.8	577

阶段	类型	数量	t_h/℃ 范围/均值	t_m,ice/℃ 范围/均值	t_m,cla/℃ 范围/均值	t_m,s/℃ 范围/均值
Ⅰ	V-L	36	365~405/388	-8.0~-5.0/-6.4
Ⅰ	CO₂-H₂O	16	371~398/385		3.0~5.0/4.6
Ⅱ	V-L	40	335~390/367	-5.5~-2.0/-3.4
	CO₂-H₂O	18	352~376/367		5.0~7.0/5.8
	V-L-S	9	345~370/357			255~272/265
Ⅲ	V-L	38	275~367/339	-3.2~-1.0/-2.1
	CO₂-H₂O	15	331~359/345		7.0~8.0/7.4
	V-L-S	18	270~330/309			242~295/256

阶段	类型	数量	t_h/℃ 范围/均值	t_m,ice/℃ 范围/均值	t_m,cla/℃ 范围/均值	t_m,s/℃ 范围/均值
Ⅰ	V-L	36	365~405/388	-8.0~-5.0/-6.4
Ⅰ	CO₂-H₂O	16	371~398/385		3.0~5.0/4.6
Ⅱ	V-L	40	335~390/367	-5.5~-2.0/-3.4
	CO₂-H₂O	18	352~376/367		5.0~7.0/5.8
	V-L-S	9	345~370/357			255~272/265
Ⅲ	V-L	38	275~367/339	-3.2~-1.0/-2.1
	CO₂-H₂O	15	331~359/345		7.0~8.0/7.4
	V-L-S	18	270~330/309			242~295/256