Geological Characteristics and Genesis of the Xiangtanzi Gold Deposit in Liangdang County, Gansu Province

doi:10.19657/j.geoscience.1000-8527.2021.127

Abstract

Abstract:

The Xiangtanzi gold deposit is located in the eastern West Qinling orogenic belt. The gold deposit is mainly controlled by NW-trending faults, and is closely related to the local intermediate-felsic dikes. Microscopic observation and electron microprobe analysis show that Au is mainly hosted in pyrite and arsenopyrite. The Co/Ni characteristics of pyrite in the ore body show that the genesis of pyrite is related to magmatism. Through REE analysis, it is found that REE characteristics of ore are basically consistent with those of rock mass, but obviously different from those of surrounding rock.The sulfur isotope of pyrite in the ore was tested and the ore sulfide δ³⁴S values are from -5.7‰ to 2.0‰ (avg.0.38‰), clustering around zero with a tower distribution, which indicates that the ore sulfur source is magmatic. By hydrogen and oxygen isotope analysis, the Xiangtanzi gold ore has δ¹⁸${{\text{O}}_{{{\text{H}}_{2}}\text{O}}}$=3.44‰-9.65‰ (avg.6.29‰) and δD=-120.10‰ to -79.00‰ (avg.-100.47‰). This indicates that the ore-forming fluid in this area came mainly from magmatic water.Pb isotope characteristics indicates that the Pb evolution at Xiangtanzi was closely related to magmatism and orogeny. A comparative study shows that the metallogenic epoch of the Xiangtanzi gold deposit is late Indosinian. The Xiangtanzi gold deposit is a vein shaped ore body controlled by shallow fault system, which was invaded by magma containing ore-forming materials and fluids in the late Indosinian period. The discovery and genesis of Xiangtanzi gold deposit is of great significance to the prospecting direction in West Qinling area.

Key words: West Qinling orogenic belt, Xiangtanzi gold deposit, geological characteristic, geochemical characteristic, ore genesis

CLC Number:

P618.51

GAO Yinhu, YIN Gang, GONG Zeqiang, GUO Mingchun. Geological Characteristics and Genesis of the Xiangtanzi Gold Deposit in Liangdang County, Gansu Province[J]. Geoscience, 2021, 35(06): 1523-1535.

Figures/Tables 18

Fig.1 Tectonic map of the Xiangtanzi gold deposit

Fig.2 Geological map of the Xiangtanzi mining area

Fig.3 Geological profile of No.25 exploration line of the Xiangtanzi gold deposit

Fig.4 Photos of representative ore mineral assemblages of the Xiangtanzi gold deposit

Fig.5 Photomicrographs of pyrite in each ore stage of the Xiangtanzi gold deposit

Table 1 EPMA results of pyrites from the Xiangtanzi gold deposit (%)

样品号	取样位置	As	Fe	S	Au	Zn	Co	Ag	Ni	总量	Co/Ni
X1-1	Ⅰ矿带	4.40	44.05	52.22	0.06	0.02	0.14	0	0.04	100.93	3.97
X1-1	Ⅰ矿带	2.03	44.01	52.65	0	0	0.12	0	0.05	98.86	2.28
X1-1	Ⅰ矿带	2.12	43.18	53.46	0	0.14	0.08	0	0.01	98.99	16.00
X1-1	Ⅰ矿带	1.76	44.76	53.03	0	0.06	0.07	0.01	0.03	99.72	2.45
X1-1	Ⅰ矿带	0.53	45.93	52.90	0.11	0.17	0.07	0	0.08	99.79	0.91
X1-2	Ⅰ矿带	0.14	46.66	53.09	0.08	0.03	0.07	0.03	0.01	100.11	4.64
X1-2	Ⅰ矿带	0.17	45.60	54.23	0.02	0.11	0.17	0	0.02	100.32	11.20
X1-2	Ⅰ矿带	0.19	44.51	54.86	0	0.03	0.10	0.05	0.22	99.96	0.44
X1-2	Ⅰ矿带	0.19	45.24	53.17	0.11	0.13	0.08	0.02	0.03	98.97	2.81
X1-2	Ⅰ矿带	0.18	44.94	53.91	0.03	0.01	0.05	0	0.02	99.14	3.33
X1-2	Ⅰ矿带	0.21	45.21	54.71	0	0	0.16	0	0.11	100.40	1.45
K1-11	Ⅲ矿带	0.20	45.99	53.31	0.10	0	0.05	0	0.02	99.67	2.35
Z15-4	Ⅱ矿带	0.20	47.42	51.97	0	0	0.04	0.01	0.08	99.72	0.52
Z8-1	Ⅱ矿带	0.22	43.71	55.29	0	0.07	0.06	0	0.08	99.54	0.73
Z8-2	Ⅱ矿带	0.16	45.96	52.60	0	0	0.11	0.02	0.05	98.90	2.35
Z8-3	Ⅱ矿带	0.26	46.09	52.10	0	0.01	0.35	0.02	0.03	98.86	11.23
LI-1	Ⅱ矿带	0.23	45.17	53.87	0	0.02	0.10	0	0.06	99.45	1.75
LI-1	Ⅱ矿带	0.29	45.98	53.75	0.03	0.07	0.06	0	0.02	100.20	3.00
Z20-2	Ⅱ矿带	0.25	44.94	54.08	0	0.07	0.08	0.02	0.16	99.60	0.52

Table 2 EPMA results of arsenopyrite from the Xiangtanzi gold deposit (%)

编号	As	Fe	S	Cu	Zn	Co	Ag	Au	总量
Apy1	44.69	34.69	20.38	0.01	0.03	0.07	0.01	0	99.88
Apy2	44.92	34.70	20.77	0.07	0.01	0.06	0.04	0	100.57
Apy3	44.58	34.78	20.89	0.01	0	0.07	0	0	100.33
Apy4	45.11	34.62	20.27	0	0.03	0.09	0	0	100.12
Apy5	42.09	35.33	23.59	0	0.05	0.11	0.01	0.090	101.27
Apy6	42.48	34.74	22.54	0	0.02	0.05	0	0.005	99.84

Table 3 REE parameters of the orebody, wallrock and intrusion at the Xiangtanzi gold deposit (10-6)

样品号	样品名	取样位置	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er
1	X1-1	矿体	45.57	89.37	10.03	36.16	8.56	1.43	6.12	0.90	5.00	1.01	2.83
2	X1-2	矿体	83.54	155.95	16.74	60.02	12.16	2.31	7.34	0.77	3.10	0.53	1.30
3	Z3	矿体	77.96	140.96	14.48	49.96	9.69	2.23	6.25	0.73	3.35	0.62	1.70
4	Z4	矿体	84.20	144.01	14.59	49.26	9.52	2.07	6.22	0.71	3.29	0.61	1.67
5	Z5	矿体	84.17	150.66	15.47	53.03	10.31	2.31	6.59	0.74	3.23	0.59	1.60
6	K1-10	矿体	82.88	149.61	15.46	52.04	10.27	2.33	6.53	0.75	3.43	0.63	1.73
7	K1-11	矿体	84.87	150.76	15.47	50.87	10.21	2.20	6.43	0.73	3.23	0.59	1.61
8	L06-1	围岩	19.80	36.20	4.28	17.40	3.39	0.98	2.92	0.52	2.84	0.55	1.46
9	L97-8	围岩	21.70	35.20	3.94	15.40	3.07	0.87	2.87	0.52	2.99	0.62	1.82
10	DB02-1	岩体	104.00	170.00	18.40	64.70	9.82	2.31	7.47	0.93	3.72	0.69	1.97
11	FSD01	岩体	103.00	181.00	20.30	75.80	11.60	2.73	8.51	1.07	4.01	0.65	1.85
样品号	样品名	取样位置	Tm	Yb	Lu	Y	REE	LREE	HREE	LREE/ HREE	La_N/ Yb_N	δEu	δCe
1	X1-1	矿体	0.42	2.67	0.40	25.36	210.47	191.12	19.35	9.88	12.24	0.60	1.02
2	X1-2	矿体	0.18	1.08	0.16	13.57	345.18	330.72	14.46	22.87	55.48	0.75	1.02
3	Z3	矿体	0.25	1.63	0.25	16.89	310.06	295.28	14.78	19.98	34.31	0.88	1.03
4	Z4	矿体	0.25	1.63	0.26	16.47	318.29	303.65	14.64	20.74	37.05	0.82	1.01
5	Z5	矿体	0.24	1.57	0.25	15.86	330.76	315.95	14.81	21.33	38.46	0.86	1.02
6	K1-10	矿体	0.25	1.65	0.26	17.58	327.82	312.59	15.23	20.52	36.03	0.87	1.02
7	K1-11	矿体	0.24	1.57	0.25	16.15	329.03	314.38	14.65	21.46	38.78	0.83	1.02
8	L06-1	围岩	0.24	1.48	0.19	15.20	92.25	82.05	10.20	8.05	9.60	0.95	0.96
9	L97-8	围岩	0.30	1.96	0.27	17.70	91.53	80.18	11.36	7.06	7.94	0.89	0.93
10	DB02-1	岩体	0.30	1.94	0.28	20.30	386.51	369.23	17.28	21.36	38.45	0.82	0.95
11	FSD01	岩体	0.25	1.58	0.21	18.80	412.56	394.43	18.13	21.76	46.76	0.84	0.97

Table 3 REE parameters of the orebody, wallrock and intrusion at the Xiangtanzi gold deposit (10-6)

样品号	样品名	取样位置	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er
1	X1-1	矿体	45.57	89.37	10.03	36.16	8.56	1.43	6.12	0.90	5.00	1.01	2.83
2	X1-2	矿体	83.54	155.95	16.74	60.02	12.16	2.31	7.34	0.77	3.10	0.53	1.30
3	Z3	矿体	77.96	140.96	14.48	49.96	9.69	2.23	6.25	0.73	3.35	0.62	1.70
4	Z4	矿体	84.20	144.01	14.59	49.26	9.52	2.07	6.22	0.71	3.29	0.61	1.67
5	Z5	矿体	84.17	150.66	15.47	53.03	10.31	2.31	6.59	0.74	3.23	0.59	1.60
6	K1-10	矿体	82.88	149.61	15.46	52.04	10.27	2.33	6.53	0.75	3.43	0.63	1.73
7	K1-11	矿体	84.87	150.76	15.47	50.87	10.21	2.20	6.43	0.73	3.23	0.59	1.61
8	L06-1	围岩	19.80	36.20	4.28	17.40	3.39	0.98	2.92	0.52	2.84	0.55	1.46
9	L97-8	围岩	21.70	35.20	3.94	15.40	3.07	0.87	2.87	0.52	2.99	0.62	1.82
10	DB02-1	岩体	104.00	170.00	18.40	64.70	9.82	2.31	7.47	0.93	3.72	0.69	1.97
11	FSD01	岩体	103.00	181.00	20.30	75.80	11.60	2.73	8.51	1.07	4.01	0.65	1.85
样品号	样品名	取样位置	Tm	Yb	Lu	Y	REE	LREE	HREE	LREE/ HREE	La_N/ Yb_N	δEu	δCe
1	X1-1	矿体	0.42	2.67	0.40	25.36	210.47	191.12	19.35	9.88	12.24	0.60	1.02
2	X1-2	矿体	0.18	1.08	0.16	13.57	345.18	330.72	14.46	22.87	55.48	0.75	1.02
3	Z3	矿体	0.25	1.63	0.25	16.89	310.06	295.28	14.78	19.98	34.31	0.88	1.03
4	Z4	矿体	0.25	1.63	0.26	16.47	318.29	303.65	14.64	20.74	37.05	0.82	1.01
5	Z5	矿体	0.24	1.57	0.25	15.86	330.76	315.95	14.81	21.33	38.46	0.86	1.02
6	K1-10	矿体	0.25	1.65	0.26	17.58	327.82	312.59	15.23	20.52	36.03	0.87	1.02
7	K1-11	矿体	0.24	1.57	0.25	16.15	329.03	314.38	14.65	21.46	38.78	0.83	1.02
8	L06-1	围岩	0.24	1.48	0.19	15.20	92.25	82.05	10.20	8.05	9.60	0.95	0.96
9	L97-8	围岩	0.30	1.96	0.27	17.70	91.53	80.18	11.36	7.06	7.94	0.89	0.93
10	DB02-1	岩体	0.30	1.94	0.28	20.30	386.51	369.23	17.28	21.36	38.45	0.82	0.95
11	FSD01	岩体	0.25	1.58	0.21	18.80	412.56	394.43	18.13	21.76	46.76	0.84	0.97

Fig.6 REE distribution patterns of the orebody, wallrock and intrusion at the Xiangtanzi gold deposit (normalized data after reference[20])

Table 4 Results of sulfur isotope analysis of the Xiangtanzi gold deposit (‰)

序号	样品编号	取样矿带	测试矿物	δ³⁴S
1	X1-1	Ⅰ	黄铁矿	-5.7
2	X1-2	Ⅰ	黄铁矿	1.8
3	K1-33	Ⅱ	黄铁矿	2.0
4	K1-31	Ⅱ	黄铁矿	1.8
5	K1-11	Ⅲ	黄铁矿	2.0

Table 5 Results of hydrogen and oxygen isotope analysis of the Xiangtanzi gold deposit(‰)

样品编号	取样矿带	成矿阶段	δ¹⁸ $O H 2 O$	δD
H1	Ⅲ	无矿石英阶段	3.44	-79.0
H2	Ⅲ	石英黄铁矿阶段	6.13	-91.1
H3	Ⅲ	石英黄铁矿阶段	7.12	-91.8
H4	Ⅲ	石英多金属阶段	9.65	-102.2
H5	Ⅲ	碳酸盐阶段	7.14	-118.6
H6	Ⅲ	碳酸盐阶段	4.27	-120.1

Table 5 Results of hydrogen and oxygen isotope analysis of the Xiangtanzi gold deposit(‰)

样品编号	取样矿带	成矿阶段	δ¹⁸ $O H 2 O$	δD
H1	Ⅲ	无矿石英阶段	3.44	-79.0
H2	Ⅲ	石英黄铁矿阶段	6.13	-91.1
H3	Ⅲ	石英黄铁矿阶段	7.12	-91.8
H4	Ⅲ	石英多金属阶段	9.65	-102.2
H5	Ⅲ	碳酸盐阶段	7.14	-118.6
H6	Ⅲ	碳酸盐阶段	4.27	-120.1

Table 6 Lead isotope compositions of samples from the Xiangtanzi gold deposit

样号	采样位置	²⁰⁶Pb/²⁰⁴Pb	²⁰⁷Pb/²⁰⁴Pb	²⁰⁸Pb/²⁰⁴Pb	μ	ω	Th/U	Δβ	Δγ
T014	17号巷道	18.041	15.556	38.148	9.42	36.95	3.80	16.17	34.59
T018	Ⅲ-18	18.026	15.553	38.132	9.41	36.94	3.80	16.01	34.48
T020	Ⅲ-1	18.001	15.545	38.110	9.40	36.92	3.80	15.59	34.31
T029	PD1660	18.059	15.596	38.331	9.50	38.02	3.87	19.04	41.16

Fig.7 Lead isotope diagrams of sulfide ore from the Xiangtanzi gold deposit

Fig.8 Lead isotope Δβ-Δγ classification plot for samples from the Xiangtanzi gold deposit (base map from reference [22])

Fig.9 Pyrite Co-Ni diagram for different orebodies of the Xiangtanzi gold deposit (base map from reference [26])

Fig.10 δ34S frequency diagram of the Xiangtanzi gold deposit

Fig.11 Hydrogen-oxygen isotope diagram of samples from the Xiangtanzi gold deposit

Fig.12 Metallogenic geological model of the Xiangtanzi gold deposit

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