Properties of Ore-forming Fluids and Genesis of the Xiaoxigong Gold Deposit in the Beishan Region, Gansu Province

doi:10.19657/j.geoscience.1000-8527.2020.03.12

Abstract

Abstract:

The Xiaoxigong gold deposit is located in the south part of the Beishan orogenic belt. The orebodies are hosted in metamorphic rocks of the Middle Proterozoic Xijianshan Group, and are controlled by the NWW- trending secondary faults. Mineralization process can be divided into three stages, including quartz-pyrite stage (early stage), quartz-polymetallic sulfide stage (main ore stage) and quartz-carbonate stage (late stage). In this paper, fluid inclusions, trace elements and H-O isotopes of the main ore stage are studied in order to determine the properties of the ore-forming fluids and the genesis of the deposit. The quartz of the main ore stage mainly contains H₂O-NaCl, CO₂-H₂O and pure CO₂inclusions. The homogenization temperatures, salinities and densities of H₂O-NaCl and CO₂-H₂O inclusions vary from 194 ℃ to 397 ℃, 2.2% to 8.9% and 0.63 g/cm³ to 0.98 g/cm³, respectively. According to the calculation from CO₂-H₂O three phase inclusions, the trapping pressures in the ore stage are 257 MPa to 395 MPa and the ore-forming depths are 9.5 km to 14.6 km. The results of fluid inclusion microthermometry, laser Raman spectroscopy and quartz trace elements show that the ore-forming fluid is a CO₂-H₂O-NaCl±CH₄ system and somewhat reduced, with medium-high temperature, low salinity and medium-low density. The values of δD_V-SMOW and δ¹⁸ $O H 2 O$ in the ore stage are -100.2‰ to -75.6‰ and +4.15‰ to +8.31‰.The fluid inclusion and H-O isotope characteristics indicate that the ore-forming fluids in the main ore stage were mainly metamorphic water, and the fluid immiscibility is an important mechanism for gold precipitation. Comprehensive analyses show that the Xiaoxigong deposit belongs to a mesozonal to hypozonal orogenic gold deposit.

Key words: fluid inclusion, quartz trace element, H-O isotope, orogenic gold deposit, Xiaoxigong gold deposit

CLC Number:

P618.51

YUAN Weiheng, GU Xuexiang, ZHANG Yongmei, DU Zezhong, YU Xiaofei, SUN Hairui, LÜ Xin. Properties of Ore-forming Fluids and Genesis of the Xiaoxigong Gold Deposit in the Beishan Region, Gansu Province[J]. Geoscience, 2020, 34(03): 554-568.

Figures/Tables 16

Fig.1 Simplified geotectonic location map of the Beishan orogenic belt (A),tectonic unit map of the Beishan area (B) and regional geological map of the Beishan area (C)

Fig.2 Geological map of the Xiaoxigong gold deposit

Fig.3 Ore body characteristics of the Xiaoxigong gold deposit

Fig.4 Typical ore structures, textures and mineral associations in the Xiaoxigong gold deposit

Table 1 Results of electron probe analysis for the gold minerals in the Xiaoxigong gold deposit

测点	矿物	As	Se	Fe	S	Au	Ag	Zn	Bi	Ni	Te	Cd	Sn	总量	Ag/Au	金成色
1	银金矿	—	—	0.99	0.31	54.64	42.13	0.14	0.54	—	0.10	—	—	98.85	0.77	565
2	银金矿	0.49	—	0.94	0.46	56.39	40.88	—	0.28	0.09	0.15	—	0.08	99.76	0.72	580
3	银金矿	—	—	0.27	0.33	49.93	47.77	—	0.36	—	0.11	—	—	98.77	0.96	511
4	自然金	—	—	0.33	0.23	82.51	15.20	—	0.30	0.13	0.05	0.13	0.08	98.96	0.18	844
5	金银矿	—	—	0.74	0.30	40.78	56.80	—	0.22	0.16	0.11	0.11	—	99.22	1.39	418
6	自然金	—	—	0.09	0.04	86.83	11.43	—	0.52	—	—	—	—	98.91	0.13	884
7	自然金	—	0.06	0.84	0.16	86.47	11.01	—	0.72	0.22	—	—	—	99.48	0.13	887

Fig.5 Mineralization stages of the Xiaoxigong gold deposit

Fig.6 Microphotographs of fluid inclusions in the Xiaoxigong gold deposit

Table 2 Microthermometric results of fluid inclusions in the main ore stage of the Xiaoxigong gold deposit

类型	CO₂固相初熔温度/℃	笼合物熔化温度/℃	部分均一温度/℃	冰点温度/℃	完全均一温度/℃
类型	范围/测定数/均值	范围/测定数/均值	范围/测定数/均值	范围/测定数/均值	范围/测定数/均值
Ⅰ型				-5.8~-1.5/52/-3.9	194~397/106/315
Ⅱ型	-60.1~-56.3/25/-58.3	7.4~8.9/16/7.9	16.5~26.8/28/21.7		261~389/28/320
Ⅲ型	-59.7~-56.8/11/-58.5		17.5~19.4/11/17.9

Fig.7 Histograms of homogenization temperature and salinity of fluid inclusions in the main ore stage of the Xiaoxigong gold deposit

Table 3 Fluid density, pressure and depth in the main ore stage of the Xiaoxigong gold deposit

包裹体类型	密度/(g/cm³)				压力/MPa				深度/km
包裹体类型	范围	测定数	均值		范围	测定数	均值		范围	测定数	均值
Ⅰ型	0.63~0.92	41	0.76
Ⅱ型	0.89~0.98	17	0.92	256.9~395.0		17	330	9.5~14.6		17	12.2
Ⅲ型	0.67~0.82	11	0.75

Fig.8 Laser Raman spectra of fluid inclusions in the main ore stage of the Xiaoxigong gold deposit

Table 4 Trace element concentrations and characteristic values for the main ore stage quartz of the Xiaoxigong gold deposit(10-6)

样品号	Li	Be	Sc	V	Cr	Co	Ni	Cu	Zn	Ga	Rb	Sr	Y	Mo	Cd	In	Sb
BD-5	1.890	0.074	0.426	2.050	4.16	0.095	0.168	0.525	3.340	0.598	4.370	2.110	0.046	0.006	0.019	<0.002	0.107
BD-6	1.430	0.004	0.189	0.121	3.09	0.015	0.075	0.604	0.556	0.033	0.171	2.390	0.174	0.005	0.010	<0.002	0.069
BD-7	0.665	0.002	0.541	0.035	2.95	0.013	0.192	0.104	0.481	0.015	0.031	6.210	0.252	0.004	0.015	0.002	0.079
BD-8	0.967	0.008	0.047	0.037	3.11	0.009	0.045	0.112	0.695	0.005	0.034	0.842	0.020	0.002	<0.002	<0.002	0.076
ND-1	0.062	0.011	0.298	0.038	4.11	0.009	0.136	0.075	0.703	0.009	0.031	2.000	0.215	0.003	0.003	<0.002	0.135
ND-4	0.102	0.003	8.490	0.385	3.23	0.026	0.091	0.155	0.691	0.042	0.129	0.980	0.034	0.002	0.007	<0.002	0.077
ND-16	0.265	0.063	0.383	1.180	3.45	0.185	0.231	1.770	4.590	0.359	1.180	4.570	1.030	0.043	0.015	<0.002	0.122
ND-23	0.109	0.002	0.198	0.247	3.26	0.047	0.133	0.190	0.577	0.032	0.141	1.610	0.220	0.014	0.003	<0.002	0.070
ZD-4	1.510	0.110	0.277	1.130	3.34	0.203	0.110	0.146	1.570	0.547	4.190	2.080	0.989	0.022	0.011	0.005	0.465
ZD-6	1.180	0.182	0.375	1.660	4.10	0.161	0.192	0.398	2.720	0.485	6.680	1.040	1.660	0.081	0.017	0.011	0.342
ZD-8	2.050	0.163	0.330	1.430	3.11	0.172	0.201	0.103	1.780	0.761	5.270	9.630	1.370	0.069	0.036	0.005	0.618
ZD-9	2.800	0.265	0.638	2.480	3.50	0.350	0.172	0.158	20.100	1.480	10.500	3.360	2.630	0.082	0.382	0.015	0.660
样品号	Cs	Ba	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	W
BD-5	0.152	14.300	0.044	0.082	0.010	0.031	0.005	0.003	0.007	0.002	0.007	0.002	0.006	0.002	0.006	0.002	0.367
BD-6	0.028	1.210	0.048	0.089	0.011	0.040	0.013	0.005	0.013	0.003	0.020	0.005	0.016	0.004	0.019	0.003	0.041
BD-7	0.028	0.383	0.04	0.090	0.012	0.046	0.014	0.005	0.013	0.004	0.025	0.008	0.033	0.008	0.078	0.022	0.047
BD-8	0.023	0.569	0.022	0.037	0.004	0.017	0.004	<0.002	0.003	<0.002	0.003	<0.002	0.002	<0.002	<0.002	<0.002	0.064
ND-1	0.016	0.351	0.107	0.211	0.029	0.110	0.024	0.005	0.026	0.005	0.029	0.006	0.018	0.003	0.018	0.003	0.040
ND-4	0.012	1.190	0.024	0.039	0.003	0.015	0.004	0.004	0.004	<0.002	0.005	<0.002	0.003	<0.002	0.002	<0.002	0.046
ND-16	0.039	7.170	0.538	1.220	0.167	0.642	0.149	0.036	0.126	0.026	0.160	0.036	0.105	0.018	0.106	0.013	0.242
ND-23	0.011	3.000	0.537	0.921	0.125	0.511	0.100	0.014	0.081	0.010	0.042	0.006	0.016	0.002	0.013	0.002	0.035
ZD-4	0.165	4.510	0.547	1.220	0.180	0.796	0.266	0.041	0.199	0.042	0.215	0.038	0.099	0.015	0.073	0.010	547.000
ZD-6	0.099	9.130	1.050	2.400	0.269	0.962	0.206	0.046	0.185	0.041	0.265	0.059	0.178	0.031	0.199	0.027	17.600
ZD-8	0.194	7.350	1.360	2.980	0.385	1.440	0.337	0.046	0.256	0.050	0.276	0.051	0.151	0.024	0.135	0.019	251.000
ZD-9	0.226	10.000	1.540	3.600	0.503	2.070	0.626	0.092	0.491	0.096	0.513	0.099	0.257	0.040	0.226	0.032	1 085.000
样品号	Re	Tl	Pb	Bi	Th	U	Nb	Ta	Zr	Hf	δEu	δCe	Y/Ho	Zr/Hf	Hf/Sm	Nb/La	Th/La
BD-5	<0.002	0.023	1.890	0.045	0.007	0.006	0.239	0.017	0.357	0.016	1.55	0.89	23.00	22.31	3.20	5.43	0.16
BD-6	<0.002	0.005	9.620	0.096	<0.002	0.004	0.006	<0.002	0.037	<0.002	1.16	0.88	34.80	—	—	0.13	—
BD-7	<0.002	<0.002	0.340	0.007	0.005	0.007	0.004	0.002	0.039	<0.002	1.11	0.96	31.50	—	—	0.10	0.13
BD-8	<0.002	<0.002	0.212	0.005	0.004	0.005	0.203	0.013	0.059	0.002	1.70	0.87	—	29.50	0.50	9.23	0.18
ND-1	<0.002	<0.002	0.472	0.009	0.003	0.008	0.003	<0.002	0.034	<0.002	0.61	0.88	35.83	—	—	0.03	0.03
ND-4	<0.002	<0.002	1.160	0.010	0.002	0.004	0.013	0.002	0.034	<0.002	3.03	0.93	—	—	—	0.54	0.08
ND-16	<0.002	0.005	6.990	0.006	0.074	0.025	0.062	0.006	0.969	0.030	0.78	0.95	28.61	32.30	0.20	0.12	0.14
ND-23	<0.002	0.002	0.945	0.008	0.006	0.008	0.003	<0.002	0.034	<0.002	0.46	0.81	36.67	—	—	0.01	0.01
ZD-4	0.007	0.071	94.100	2.010	0.098	0.052	0.195	0.012	0.968	0.035	0.52	0.91	26.03	27.66	0.13	0.36	0.18
ZD-6	<0.002	0.048	0.673	0.013	0.223	0.151	0.503	0.031	25.900	0.753	0.71	1.04	28.14	34.40	3.66	0.48	0.21
ZD-8	0.003	0.046	55.600	1.660	0.340	0.074	0.675	0.041	1.600	0.059	0.46	0.96	26.86	27.12	0.18	0.50	0.25
ZD-9	0.013	0.122	217.000	6.640	0.286	0.233	0.868	0.053	2.220	0.077	0.49	0.96	26.57	28.83	0.12	0.56	0.19

Table 4 Trace element concentrations and characteristic values for the main ore stage quartz of the Xiaoxigong gold deposit(10-6)

样品号	Li	Be	Sc	V	Cr	Co	Ni	Cu	Zn	Ga	Rb	Sr	Y	Mo	Cd	In	Sb
BD-5	1.890	0.074	0.426	2.050	4.16	0.095	0.168	0.525	3.340	0.598	4.370	2.110	0.046	0.006	0.019	<0.002	0.107
BD-6	1.430	0.004	0.189	0.121	3.09	0.015	0.075	0.604	0.556	0.033	0.171	2.390	0.174	0.005	0.010	<0.002	0.069
BD-7	0.665	0.002	0.541	0.035	2.95	0.013	0.192	0.104	0.481	0.015	0.031	6.210	0.252	0.004	0.015	0.002	0.079
BD-8	0.967	0.008	0.047	0.037	3.11	0.009	0.045	0.112	0.695	0.005	0.034	0.842	0.020	0.002	<0.002	<0.002	0.076
ND-1	0.062	0.011	0.298	0.038	4.11	0.009	0.136	0.075	0.703	0.009	0.031	2.000	0.215	0.003	0.003	<0.002	0.135
ND-4	0.102	0.003	8.490	0.385	3.23	0.026	0.091	0.155	0.691	0.042	0.129	0.980	0.034	0.002	0.007	<0.002	0.077
ND-16	0.265	0.063	0.383	1.180	3.45	0.185	0.231	1.770	4.590	0.359	1.180	4.570	1.030	0.043	0.015	<0.002	0.122
ND-23	0.109	0.002	0.198	0.247	3.26	0.047	0.133	0.190	0.577	0.032	0.141	1.610	0.220	0.014	0.003	<0.002	0.070
ZD-4	1.510	0.110	0.277	1.130	3.34	0.203	0.110	0.146	1.570	0.547	4.190	2.080	0.989	0.022	0.011	0.005	0.465
ZD-6	1.180	0.182	0.375	1.660	4.10	0.161	0.192	0.398	2.720	0.485	6.680	1.040	1.660	0.081	0.017	0.011	0.342
ZD-8	2.050	0.163	0.330	1.430	3.11	0.172	0.201	0.103	1.780	0.761	5.270	9.630	1.370	0.069	0.036	0.005	0.618
ZD-9	2.800	0.265	0.638	2.480	3.50	0.350	0.172	0.158	20.100	1.480	10.500	3.360	2.630	0.082	0.382	0.015	0.660
样品号	Cs	Ba	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	W
BD-5	0.152	14.300	0.044	0.082	0.010	0.031	0.005	0.003	0.007	0.002	0.007	0.002	0.006	0.002	0.006	0.002	0.367
BD-6	0.028	1.210	0.048	0.089	0.011	0.040	0.013	0.005	0.013	0.003	0.020	0.005	0.016	0.004	0.019	0.003	0.041
BD-7	0.028	0.383	0.04	0.090	0.012	0.046	0.014	0.005	0.013	0.004	0.025	0.008	0.033	0.008	0.078	0.022	0.047
BD-8	0.023	0.569	0.022	0.037	0.004	0.017	0.004	<0.002	0.003	<0.002	0.003	<0.002	0.002	<0.002	<0.002	<0.002	0.064
ND-1	0.016	0.351	0.107	0.211	0.029	0.110	0.024	0.005	0.026	0.005	0.029	0.006	0.018	0.003	0.018	0.003	0.040
ND-4	0.012	1.190	0.024	0.039	0.003	0.015	0.004	0.004	0.004	<0.002	0.005	<0.002	0.003	<0.002	0.002	<0.002	0.046
ND-16	0.039	7.170	0.538	1.220	0.167	0.642	0.149	0.036	0.126	0.026	0.160	0.036	0.105	0.018	0.106	0.013	0.242
ND-23	0.011	3.000	0.537	0.921	0.125	0.511	0.100	0.014	0.081	0.010	0.042	0.006	0.016	0.002	0.013	0.002	0.035
ZD-4	0.165	4.510	0.547	1.220	0.180	0.796	0.266	0.041	0.199	0.042	0.215	0.038	0.099	0.015	0.073	0.010	547.000
ZD-6	0.099	9.130	1.050	2.400	0.269	0.962	0.206	0.046	0.185	0.041	0.265	0.059	0.178	0.031	0.199	0.027	17.600
ZD-8	0.194	7.350	1.360	2.980	0.385	1.440	0.337	0.046	0.256	0.050	0.276	0.051	0.151	0.024	0.135	0.019	251.000
ZD-9	0.226	10.000	1.540	3.600	0.503	2.070	0.626	0.092	0.491	0.096	0.513	0.099	0.257	0.040	0.226	0.032	1 085.000
样品号	Re	Tl	Pb	Bi	Th	U	Nb	Ta	Zr	Hf	δEu	δCe	Y/Ho	Zr/Hf	Hf/Sm	Nb/La	Th/La
BD-5	<0.002	0.023	1.890	0.045	0.007	0.006	0.239	0.017	0.357	0.016	1.55	0.89	23.00	22.31	3.20	5.43	0.16
BD-6	<0.002	0.005	9.620	0.096	<0.002	0.004	0.006	<0.002	0.037	<0.002	1.16	0.88	34.80	—	—	0.13	—
BD-7	<0.002	<0.002	0.340	0.007	0.005	0.007	0.004	0.002	0.039	<0.002	1.11	0.96	31.50	—	—	0.10	0.13
BD-8	<0.002	<0.002	0.212	0.005	0.004	0.005	0.203	0.013	0.059	0.002	1.70	0.87	—	29.50	0.50	9.23	0.18
ND-1	<0.002	<0.002	0.472	0.009	0.003	0.008	0.003	<0.002	0.034	<0.002	0.61	0.88	35.83	—	—	0.03	0.03
ND-4	<0.002	<0.002	1.160	0.010	0.002	0.004	0.013	0.002	0.034	<0.002	3.03	0.93	—	—	—	0.54	0.08
ND-16	<0.002	0.005	6.990	0.006	0.074	0.025	0.062	0.006	0.969	0.030	0.78	0.95	28.61	32.30	0.20	0.12	0.14
ND-23	<0.002	0.002	0.945	0.008	0.006	0.008	0.003	<0.002	0.034	<0.002	0.46	0.81	36.67	—	—	0.01	0.01
ZD-4	0.007	0.071	94.100	2.010	0.098	0.052	0.195	0.012	0.968	0.035	0.52	0.91	26.03	27.66	0.13	0.36	0.18
ZD-6	<0.002	0.048	0.673	0.013	0.223	0.151	0.503	0.031	25.900	0.753	0.71	1.04	28.14	34.40	3.66	0.48	0.21
ZD-8	0.003	0.046	55.600	1.660	0.340	0.074	0.675	0.041	1.600	0.059	0.46	0.96	26.86	27.12	0.18	0.50	0.25
ZD-9	0.013	0.122	217.000	6.640	0.286	0.233	0.868	0.053	2.220	0.077	0.49	0.96	26.57	28.83	0.12	0.56	0.19

Fig.9 REE distribution patterns of the main ore stage quartz of the Xiaoxigong gold deposit

Table 5 Hydrogen and oxygen isotope compositions of quartz in the Xiaoxigong gold deposit

序号
1	BD-5	北矿带石英脉型	石英	-90.6	14.0	300	7.1	本文
2	BD-6	北矿带石英脉型	石英	-94.9	13.6	300	6.7
3	BD-7	北矿带石英脉型	石英	-88.9	13.9	340	8.3
4	BD-8	北矿带石英脉型	石英	-88.3	11.7	300	4.8
5	ND-1	南矿带石英脉型	石英	-81.0	12.9	280	5.3
6	ND-4	南矿带石英脉型	石英	-75.6	11.8	280	4.2
7	ND-16	南矿带石英脉型	石英	-77.6	13.3	280	5.7
8	ND-23	南矿带石英脉型	石英	-81.8	12.5	280	4.9
9	ZD-4	中矿带石英脉型	石英	-92.9	12.0	320	5.8
10	ZD-6	中矿带石英脉型	石英	-100.2	12.8	320	6.6
11	ZD-8	中矿带石英脉型	石英	-95.7	13.3	320	7.1
12	ZD-9	中矿带石英脉型	石英	-94.3	13.2	320	7.0
13	XXG9901	早期含金黄铜矿-石英脉	石英	-115.9	10.9	285	3.5	聂凤军等^[8]
14	XXG9902	早期含金黄铜矿-石英脉	石英	-103.0	12.5	300	5.6
15	XXG9903	晚期含金多金属硫化物-石英脉	石英	-90.6	13.9	280	6.3
16	XXG9904	晚期含金多金属硫化物-石英脉	石英	-115.0	9.7	279	2.0
17	XXG9905	晚期含金多金属硫化物-石英脉	石英	-109.4	11.6	270	3.5
18	XXG9906	蚀变岩型	石英	-83.6	6.6	248	-2.4
19	XXG9907	蚀变岩型	石英	-82.0	8.5	274	0.6
20	XXG9908	蚀变岩型	石英	-83.7	9.3	268	1.2
21	XXG9909	蚀变岩型	石英	-82.5	13.1	276	5.3
22	XXG9910	蚀变岩型	石英	-94.6	9.9	254	1.1
23	XXG05-6	石英脉型	石英	-76.0	12.4	219	1.8	胡朋^[28]
24	XXG05-10	石英脉型	石英	-90.0	9.5	219	-1.1
25	XXG05-12	石英脉型	石英	-80.0	9.6	219	-1.0
26	XXG05-20	石英脉型	石英	-83.0	11.7	241.6	2.3
27	B80-2	石英脉型	石英	-96.0	13.6	230	3.6	陈柏林^[15]
28	B80-3	石英脉型	石英	-102.0	13.4	224	3.1
29	B80-4	石英脉型	石英	-107.0	13.8	191	1.5
30	B4	石英脉型	石英	-126.0	14.2	250	5.3
31	B5	石英脉型	石英	-72.5	14.97	250	6.0
32	XX-5	石英脉型	石英	-99.6	14.2	400	10.1	刘伟等^[10]
33	XX-7	石英脉型	石英	-99.0	13.9	400	9.8
34	XX-10	石英脉型	石英	-109.3	12.6	400	8.5
35	XXG-15	中矿带石英脉型	石英	-84.0	13.4	300	6.5	朱江^[11]
36	XXG-19	中矿带石英脉型	石英	-102.0	13.6	300	6.7
37	XXG-14	中矿带石英脉型	石英	-107.0	13.3	300	6.4

Table 5 Hydrogen and oxygen isotope compositions of quartz in the Xiaoxigong gold deposit

序号
1	BD-5	北矿带石英脉型	石英	-90.6	14.0	300	7.1	本文
2	BD-6	北矿带石英脉型	石英	-94.9	13.6	300	6.7
3	BD-7	北矿带石英脉型	石英	-88.9	13.9	340	8.3
4	BD-8	北矿带石英脉型	石英	-88.3	11.7	300	4.8
5	ND-1	南矿带石英脉型	石英	-81.0	12.9	280	5.3
6	ND-4	南矿带石英脉型	石英	-75.6	11.8	280	4.2
7	ND-16	南矿带石英脉型	石英	-77.6	13.3	280	5.7
8	ND-23	南矿带石英脉型	石英	-81.8	12.5	280	4.9
9	ZD-4	中矿带石英脉型	石英	-92.9	12.0	320	5.8
10	ZD-6	中矿带石英脉型	石英	-100.2	12.8	320	6.6
11	ZD-8	中矿带石英脉型	石英	-95.7	13.3	320	7.1
12	ZD-9	中矿带石英脉型	石英	-94.3	13.2	320	7.0
13	XXG9901	早期含金黄铜矿-石英脉	石英	-115.9	10.9	285	3.5	聂凤军等^[8]
14	XXG9902	早期含金黄铜矿-石英脉	石英	-103.0	12.5	300	5.6
15	XXG9903	晚期含金多金属硫化物-石英脉	石英	-90.6	13.9	280	6.3
16	XXG9904	晚期含金多金属硫化物-石英脉	石英	-115.0	9.7	279	2.0
17	XXG9905	晚期含金多金属硫化物-石英脉	石英	-109.4	11.6	270	3.5
18	XXG9906	蚀变岩型	石英	-83.6	6.6	248	-2.4
19	XXG9907	蚀变岩型	石英	-82.0	8.5	274	0.6
20	XXG9908	蚀变岩型	石英	-83.7	9.3	268	1.2
21	XXG9909	蚀变岩型	石英	-82.5	13.1	276	5.3
22	XXG9910	蚀变岩型	石英	-94.6	9.9	254	1.1
23	XXG05-6	石英脉型	石英	-76.0	12.4	219	1.8	胡朋^[28]
24	XXG05-10	石英脉型	石英	-90.0	9.5	219	-1.1
25	XXG05-12	石英脉型	石英	-80.0	9.6	219	-1.0
26	XXG05-20	石英脉型	石英	-83.0	11.7	241.6	2.3
27	B80-2	石英脉型	石英	-96.0	13.6	230	3.6	陈柏林^[15]
28	B80-3	石英脉型	石英	-102.0	13.4	224	3.1
29	B80-4	石英脉型	石英	-107.0	13.8	191	1.5
30	B4	石英脉型	石英	-126.0	14.2	250	5.3
31	B5	石英脉型	石英	-72.5	14.97	250	6.0
32	XX-5	石英脉型	石英	-99.6	14.2	400	10.1	刘伟等^[10]
33	XX-7	石英脉型	石英	-99.0	13.9	400	9.8
34	XX-10	石英脉型	石英	-109.3	12.6	400	8.5
35	XXG-15	中矿带石英脉型	石英	-84.0	13.4	300	6.5	朱江^[11]
36	XXG-19	中矿带石英脉型	石英	-102.0	13.6	300	6.7
37	XXG-14	中矿带石英脉型	石英	-107.0	13.3	300	6.4

Fig.10 Plots of δ18O-δD for the ore-forming fluids in the Xiaoxigong gold deposit

Table 6 Comparison of characteristics between the Xiaoxigong gold deposit and typical orogenic gold deposits

特征	小西弓金矿床	造山型金矿床
构造背景	北山造山带挤压形成的韧性剪切带中	汇聚板块边缘或陆内碰撞造山带
控矿构造	NWW向次级断裂、韧性剪切带	区域断裂或者韧性剪切带的次级构造
赋矿围岩	中元古界西尖山群中浅变质岩	绿片岩相-角闪岩相变质地体
矿体形态	脉状、透镜体状	一般以脉状、似层状为主
矿石组分	以黄铁矿和毒砂为主(≤ 5%),脉石矿物主要为石英	含有≤ 3%~ 5%的硫化物,脉石矿物以石英为主
围岩蚀变	硅化、绢云母化、萤石化、碳酸盐化	硅化、绢云母化、碳酸盐化、绿泥石化等
成矿流体成分	CO₂-H₂O-NaCl±CH₄体系	CO₂-H₂O-NaCl,含CH₄及少量N₂
成矿流体温度、盐度	194~397 ℃,2.2%~8.9% NaCl_eqv	200~500 ℃,3%~10%NaCl_eqv
成矿流体来源	以变质水为主	变质水
成矿时间	与造山作用时间基本吻合(284~276 Ma)	与造山作用同时或稍晚于造山作用

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