Surface Indicators for Deep Mineralization in the Lutangba-Axizhai Area of Gejiu, Yunnan Province: Implications from Tectonic Alteration and Primary Geochemical Halos

doi:10.19657/j.geoscience.1000-8527.2023.057

Abstract

Abstract:

Interlayer oxidized tin ore is a significant mineralization type in the Gaosong orefield at Gejiu. Enhancing the study and exploration for this type of tin mineralization is important to relieve resource crisis and increase the reserve for exhausting mines. We study the surface tectonic alteration and primary geochemical halo in the Lutangba-Axizhai area which shows beneficial mineralization conditions for interlayer oxidized deposits, to provide a new basis for their exploration. Field geological survey exhabits that the surface mineralization/alteration is mainly composed of iron alteration, argillization and calcite veins. It is commonly controlled by faults, especially at the intersection of NE- and EW-trending ones. The integrated analysis of 13 key elements in the altered rocks and wallrocks suggests that Cd, As, Sb, Pb and Zn are potential indicators for Sn orebody. The integrated anomaly distribution of primary geochemical halos in combination with the characteristics of structural alteration zones delineate four metallogenic target zones (Ⅰ to Ⅳ). Comparation and analysis on the front-, near- and rear-halo element combination characteristics of primary geochemical halos in each target area shows that target zone Ⅰ and Ⅱ seem to have deep interlayer oxidized tin ore prospecting potential; target zone Ⅲ with the oxidized ore is probably eroded on the surface, and have deep sulfide ore potential; target zone Ⅳ likely has small amount of uneroded remnant orebodies at depth.

Key words: Gaosong ore field, layer oxidize tin ore, primary halo, structural alteration, Gejiu tin mine

CLC Number:

CHANG Huacheng, JIAO Qianqian, JIANG Xiaojun, FAN Zhuguo, LU Lei, RUAN Banlang, DENG Mei. Surface Indicators for Deep Mineralization in the Lutangba-Axizhai Area of Gejiu, Yunnan Province: Implications from Tectonic Alteration and Primary Geochemical Halos[J]. Geoscience, 2023, 37(06): 1538-1552.

Figures/Tables 13

Fig.1 Tectonic location (a) and geological sketch map (b) of the Gejiu mining area, Yunnan Province (modified after No.308 Geological Team[34])

Fig.2 Structural alteration geological map of the Lutangba-Axizhai area (a) (modified after No.308 Geological Team[34]) and A-A' geological profile (b)

Fig.3 Field photographs and microphotographs of wallrocks and ores of the Lutangba-Axizhai area

Fig.4 Sampling location (a) and single element anomaly ((b)-(n)) of the Lutangba-Axizhai area

Fig.5 X-ray diffraction diagrams of altered rock and interlayer oxidized ore of the Lutangba-Axizhai area

Table 1 X-ray diffraction test results of altered rocks and interlayer oxidized ore of the Lutangba-Axizhai area

岩石类型	样品编号	采样位置	主要矿物组成(%)
岩石类型	样品编号	采样位置	方解石	石英	白云石	高岭石	蛇纹石	赤铁矿
中度蚀变岩	2433	地表	82.4	9.2	1.3	6.6	0	0.5
中度蚀变岩	2434	地表	87.5	3.7	0.7	7.5	0	0.6
中度蚀变岩	2437	地表	68.1	13.9	0	0	16.7	1.2
氧化矿石	2436	坑道	66.3	0	0	0	15.4	18.3

Table 2 Element contents of 1379 rock samples of the Lutangba-Axizhai area

元素	样品数	最小值 (10^-6)	最大值 (10^-6)	平均值 (10^-6)	中位数 (10^-6)	众数 (10^-6)	标准离差	变异系数	富集系数	全球碳酸盐岩^[39] (10^-6)
Sn	1379	0.01	370.00	0.92	0.37	0.26	10.30	11.25	>1.00	0.1×n
Ag	1379	0.00	5.88	0.05	0.02	0.01	0.18	3.71	>1.00	0.01×n
Cd	1379	0.02	206.00	0.63	0.22	0.13	5.63	8.98	17.91	0.04
Cu	1379	0.50	141.00	4.43	2.00	1.30	8.91	2.01	1.11	4.00
Pb	1379	0.90	5328.00	37.39	9.20	4.30	166.05	4.44	4.15	9.00
Zn	1379	4.76	3932.00	50.01	23.30	10.30	129.13	2.58	2.50	20.00
Mn	1379	7.30	13683.00	162.20	81.50	104.00	438.61	2.70	0.15	1100.00
As	1379	0.20	466.00	2.70	0.70	0.20	14.23	5.28	2.70	1.00
Sb	1379	0.05	275.00	1.81	0.54	0.05	8.65	4.77	9.07	0.20
Bi	1379	0.01	12.50	0.08	0.06	0.03	0.36	4.64	>1.00	—
Hg	1379	0.01	0.51	0.02	0.01	0.01	0.03	1.87	0.42	0.04
W	1379	0.03	1642.00	6.12	0.57	0.32	69.89	11.41	10.21	0.60
Mo	1379	0.08	29.80	0.94	0.71	0.49	1.18	1.27	2.34	0.40

Table 3 Geochemical correlation coefficients of the Lutangba-Axizhai area

元素	Sn	Ag	Cd	Cu	Pb	Zn	Mn	As	Sb	Bi	Hg	W	Mo
Sn	1.000
Ag	0.285^**	1.000
Cd	0.965^**	0.178^**	1.000
Cu	0.050	0.091^**	0.064^*	1.000
Pb	0.862^**	0.267^**	0.899^**	0.110^**	1.000
Zn	0.836^**	0.374^**	0.881^**	0.149^**	0.867^**	1.000
Mn	0.411^**	0.807^**	0.306^**	0.112^**	0.419^**	0.472^**	1.000
As	0.909^**	0.367^**	0.898^**	0.133^**	0.888^**	0.854^**	0.501^**	1.000
Sb	0.839^**	0.194^**	0.867^**	0.142^**	0.892^**	0.809^**	0.352^**	0.937^**	1.000
Bi	0.004	0.021	0.014	0.044	0.138^**	0.081^**	0.043	0.059^*	0.133^**	1.000
Hg	0.143^**	0.116^**	0.176^**	0.108^**	0.181^**	0.251^**	0.144^**	0.208^**	0.189^**	0.034	1.000
W	0.013	-0.002	0.013	0.232^**	0.013	0.007	0.008	0.017	0.019	0.014	0.004	1.000
Mo	0.641^**	0.114^**	0.657^**	0.120^**	0.599^**	0.571^**	0.205^**	0.639^**	0.621^**	0.040	0.106^**	0.020	1.000

Fig.6 R-type cluster analysis spectrum of the Lutangba-Axizhai area

Fig.7 Histograms of the representative elements (log-based) of the Lutangba-Axizhai area

Table 4 Calculated lower limit of geochemical anomalies of the Lutangba-Axizhai area

元素	极小值(10^-6)	极大值(10^-6)	平均值(10^-6)	标准离差	K	C_a	2C_a	4C_a
Sn	0.010	2.96	0.51	0.49	2.0	1.50	3.00	6.00
Ag	0.002	0.29	0.04	0.05	1.5	0.10	0.20	0.40
Cd	0.021	3.33	0.43	0.58	1.5	1.30	2.60	5.20
Cu	0.500	33.10	4.01	5.52	1.5	12.00	24.00	48.00
Pb	0.900	294.20	29.31	52.99	1.5	100.00	200.00	400.00
Zn	4.800	312.30	44.67	53.55	1.5	120.00	240.00	480.00
Mn	7.300	1038.70	144.44	178.91	1.5	400.00	800.00	1600.00
As	0.200	19.10	2.04	3.41	1.5	7.00	14.00	28.00
Sb	0.050	13.17	1.37	2.36	1.5	5.00	10.00	20.00
Bi	0.010	0.39	0.06	0.04	2.0	0.14	0.28	0.56
Hg	0.005	0.12	0.02	0.02	1.5	0.04	0.08	0.16
W	0.030	12.65	1.40	2.25	1.5	4.80	9.60	19.20
Mo	0.080	4.34	0.89	0.69	2.0	2.00	4.00	8.00

Fig.8 Anomaly characteristics of metallogenic elements of the Lutangba-Axizhai area

Table 5 Comprehensive anomaly feature statistics of the Lutangba-Axizhai area

综合异常编号	面积(km²)	元素组合	异常特征
HS-01	0.5	As-Sb-Pb- Cd-Zn-Sn	出露地层为个旧组马拉格段第一层(T₂ $g 2 1$ )灰白色厚层状白云岩,个旧组卡房段第六层(T₂ $g 1 6$ )厚层状白云岩与中厚层状灰岩互层以及个旧组卡房段第五层(T₂ $g 1 5$ )厚层白云岩与灰岩互层。区内元素异常面积大、套合好,有5个浓集中心,As、Sb、Pb和Cd二级浓度分带明显,区内断裂构造发育
HS-02	0.18	Pb-Cd-Zn- As-Sb-Sn	出露地层为个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层,个旧组马拉格段第一层(T₂ $g 2 1$ )灰白色厚层状白云岩以及个旧组卡房段第六层(T₂ $g 1 6$ )厚层状白云岩与中厚层状灰岩互层。元素异常套合好,有3个浓集中心,AS、Pb和Cd二级浓度分带明显,区内断裂构造较为发育
HS-03	0.12	Pb-As-Cd- Zn-Sn-Sb	出露地层为个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层。元素异常套合好,有2个浓集中心,Pb和Zn二级浓度分带明显,区内断裂构造较为发育
HS-04	0.09	Pb-Zn-Sn- As-Cd-Sb	出露地层为个旧组马拉格段第三层(T₂ $g 2 3$ )厚层状白云岩夹灰质白云岩。区内断裂构造极为发育,元素异常套合较好,有2个浓集中心,Pb和Zn二级浓度分带明显
HS-05	0.15	Pb-Sb-As- Cd-Zn-Sn	出露地层为个旧组马拉格段第三层(T₂ $g 2 3$ )厚层状白云岩夹灰质白云岩,个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层,区内断裂构造发育,元素异常套合较好,有3个浓集中心,As、Pb和Sb二级浓度分带明显

Table 5 Comprehensive anomaly feature statistics of the Lutangba-Axizhai area

综合异常编号	面积(km²)	元素组合	异常特征
HS-01	0.5	As-Sb-Pb- Cd-Zn-Sn	出露地层为个旧组马拉格段第一层(T₂ $g 2 1$ )灰白色厚层状白云岩,个旧组卡房段第六层(T₂ $g 1 6$ )厚层状白云岩与中厚层状灰岩互层以及个旧组卡房段第五层(T₂ $g 1 5$ )厚层白云岩与灰岩互层。区内元素异常面积大、套合好,有5个浓集中心,As、Sb、Pb和Cd二级浓度分带明显,区内断裂构造发育
HS-02	0.18	Pb-Cd-Zn- As-Sb-Sn	出露地层为个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层,个旧组马拉格段第一层(T₂ $g 2 1$ )灰白色厚层状白云岩以及个旧组卡房段第六层(T₂ $g 1 6$ )厚层状白云岩与中厚层状灰岩互层。元素异常套合好,有3个浓集中心,AS、Pb和Cd二级浓度分带明显,区内断裂构造较为发育
HS-03	0.12	Pb-As-Cd- Zn-Sn-Sb	出露地层为个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层。元素异常套合好,有2个浓集中心,Pb和Zn二级浓度分带明显,区内断裂构造较为发育
HS-04	0.09	Pb-Zn-Sn- As-Cd-Sb	出露地层为个旧组马拉格段第三层(T₂ $g 2 3$ )厚层状白云岩夹灰质白云岩。区内断裂构造极为发育,元素异常套合较好,有2个浓集中心,Pb和Zn二级浓度分带明显
HS-05	0.15	Pb-Sb-As- Cd-Zn-Sn	出露地层为个旧组马拉格段第三层(T₂ $g 2 3$ )厚层状白云岩夹灰质白云岩,个旧组马拉格段第二层(T₂ $g 2 2$ )中厚层状白云岩与白云质灰岩互层,区内断裂构造发育,元素异常套合较好,有3个浓集中心,As、Pb和Sb二级浓度分带明显

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