Geochemical genes related to granite weathering in the Yunmengshan area of Beijing, China

doi:10.13745/j.esf.sf.2020.11.11

Abstract

Abstract:

The geochemical gene technique is a new geochemical tracing technique formally proposed over the past two years. In this investigation, samples from two adjacent weathering profiles (B and C) developed in granite in the Yunmengshan area of Beijing, China were collected to test two geochemical genes named lithogene and gold metallogene. In samples from profile B, the chemical index of alteration (CIA) varied between 51.3-58.9, and the weathering index of granite (WIG) varied between 68.6-89.4, indicating incipient weathering in this profile; while in samples from profile C, CIA varied between 52.4-78.4, and WIG between 25.3-84.8, indicating intermediate weathering in profile C. The noticeable difference of weathering degrees between the two adjacent profiles indicates that different micro-environment may result in significantly different weathering products in the same granite. The lithogene similarity between samples and fresh granite varied from 85% to 100% in profile B and 90% to 100% in profile C, while the gold metallogene similarity between the two varied from 85% to 100% in profile B and 80% to 100% in profile C. With respect to top soil, the similarity of lithogenes varied from 80% to 100% in profile B and 90% to 100% in profile C, and the gold metallogene similarity varied from 85% to 100% in profile B and 80% to 100% in profile C. According to the criterion that gene similarity above 80% indicates similar genes, the lithogene and gold metallogene illustrate not only good heredity and inheritance in each profile but also high similarity between the two profiles. Besides, with respect to the ideal gold ore (gold metallogene 12020202020), the similarity of gold metallogenes varied from 25% to 50% in profile B and 30% to 50% in profile C. According to the criterion that mineralization can be recognized when the gold metallogene similarity reaches 40%, one mineralization layer of ca. 1 m thickness can be recognized in each profile. Thus, the gold metallogene may also be used as an integrated geochemical indicator in gold exploration.

Key words: weathering profiles of granite, geochemical lithogene, geochemical gold metallogene, weathering indices, micro-environment

CLC Number:

P595

WANG Xuyang, YAO Ning, GONG Qingjie, CHAO Yuede, PENG Cheng, WU Yuan. Geochemical genes related to granite weathering in the Yunmengshan area of Beijing, China[J]. Earth Science Frontiers, 2021, 28(1): 363-374.

Figures/Tables 9

References 38

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样品编号	采样深度/m	样品类型	样品描述
B1	0.3	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
B2	0.5	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B3	0.8	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B4	1.1	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B5	1.6	风化碎屑	以粗粒碎屑为主,大多粗粒手捏易碎
B6	2.0	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾
B7	2.9	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾较多
B8	3.7	风化碎屑	风化碎屑与砾石大约各占一半,残留原岩结构
B9	4.6	风化碎屑	以砾石为主,小颗粒碎屑较少,保留原岩结构
B10	5.4	风化岩石	需机械外力进行破碎,几乎无风化碎屑
B11	6.4	风化岩石	需机械外力进行破碎,无风化碎屑
B12	7	基岩	新鲜花岗岩,硬度较大
C1	0.1	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C2	0.6	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C3	1.2	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C4	1.7	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
C5	2.4	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾较多
C6	3.5	风化碎屑	以碎屑和小块砾石为主,含大块砾石,粒径为1~2 cm,锤轻击即碎
C7	4.7	风化岩石	机械外力进行破碎,无风化碎屑
C8	6	基岩	新鲜花岗岩,硬度较大

样品编号	采样深度/m	样品类型	样品描述
B1	0.3	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
B2	0.5	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B3	0.8	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B4	1.1	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
B5	1.6	风化碎屑	以粗粒碎屑为主,大多粗粒手捏易碎
B6	2.0	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾
B7	2.9	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾较多
B8	3.7	风化碎屑	风化碎屑与砾石大约各占一半,残留原岩结构
B9	4.6	风化碎屑	以砾石为主,小颗粒碎屑较少,保留原岩结构
B10	5.4	风化岩石	需机械外力进行破碎,几乎无风化碎屑
B11	6.4	风化岩石	需机械外力进行破碎,无风化碎屑
B12	7	基岩	新鲜花岗岩,硬度较大
C1	0.1	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C2	0.6	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C3	1.2	土壤	黄色土壤,含腐殖质很少,夹杂风化碎屑,风化碎屑粒径为0.1~1 mm
C4	1.7	风化碎屑	以碎屑为主,手捏可碎,粒径为0.1~1 mm
C5	2.4	风化碎屑	以粗粒碎屑为主,粒径为2~8 mm,含砾较多
C6	3.5	风化碎屑	以碎屑和小块砾石为主,含大块砾石,粒径为1~2 cm,锤轻击即碎
C7	4.7	风化岩石	机械外力进行破碎,无风化碎屑
C8	6	基岩	新鲜花岗岩,硬度较大

样品编号	采样深度/m	w_B/%
样品编号	采样深度/m	SiO₂	Al₂O₃	Fe₂O₃	K₂O	Na₂O	CaO	MgO	TiO₂	P₂O₅	MnO	LoI	总和	CO₂
B1	0.3	69.17	17.18	1.48	4.21	4.45	0.93	0.29	0.16	0.05	0.04	1.75	99.72	0.61
B2	0.5	70.05	16.72	1.86	3.92	4.09	0.86	0.26	0.15	0.04	0.07	1.70	99.73	0.23
B3	0.8	70.24	16.50	1.32	4.07	4.81	1.03	0.24	0.16	0.05	0.04	1.29	99.73	0.29
B4	1.1	67.65	17.79	1.98	4.18	5.01	1.00	0.30	0.15	0.05	0.08	1.54	99.71	0.12
B5	1.6	70.32	16.37	1.52	3.99	4.04	0.83	0.19	0.18	0.04	0.04	2.16	99.69	0.40
B6	2.0	71.64	15.61	1.48	3.96	4.16	0.88	0.18	0.13	0.05	0.05	1.55	99.70	0.21
B7	2.9	71.33	15.61	1.86	4.16	3.67	0.69	0.24	0.17	0.06	0.06	1.84	99.71	0.11
B8	3.7	70.97	15.82	1.72	4.06	3.68	0.77	0.24	0.15	0.03	0.05	2.24	99.72	0.26
B9	4.6	72.63	14.71	1.76	3.84	3.90	0.77	0.18	0.14	0.06	0.06	1.67	99.72	0.22
B10	5.4	71.89	15.34	1.69	3.98	3.94	0.77	0.17	0.14	0.06	0.06	1.67	99.70	0.10
B11	6.4	71.70	15.65	1.41	4.26	3.83	0.80	0.15	0.12	0.05	0.05	1.71	99.73	0.09
B12	7	70.77	15.89	1.60	3.86	5.26	1.44	0.16	0.14	0.07	0.06	0.45	99.69	0.09
lg(C_max/C_min)		0.03	0.08	0.18	0.05	0.16	0.32	0.28	0.17	0.31	0.32	0.70		0.84
C1	0.1	78.49	12.38	1.17	3.17	0.10	0.18	0.24	0.13	0.05	0.04	3.87	99.81	0.39
C2	0.6	75.82	14.44	0.95	3.63	0.10	0.16	0.11	0.10	0.06	0.03	4.35	99.76	0.09
C3	1.2	77.16	13.16	1.24	3.31	0.09	0.13	0.14	0.13	0.06	0.03	4.31	99.75	0.14
C4	1.7	77.21	13.18	1.12	3.64	0.12	0.13	0.15	0.14	0.06	0.03	3.96	99.74	0.31
C5	2.4	76.85	13.14	1.75	3.19	0.10	0.12	0.17	0.16	0.07	0.05	4.18	99.78	0.30
C6	3.5	82.93	9.50	1.09	2.84	0.13	0.12	0.14	0.08	0.05	0.03	2.74	99.65	0.30
C7	4.7	74.01	14.66	1.41	4.01	2.03	0.37	0.12	0.13	0.08	0.05	2.86	99.72	0.31
C8	6	70.04	16.20	1.85	3.86	5.08	1.43	0.23	0.19	0.08	0.05	0.62	99.64	0.09
lg(C_max/C_min)		0.07	0.23	0.29	0.15	1.77	1.08	0.34	0.34	0.25	0.29	0.85		0.65

样品编号	采样深度/m	w_B/%
样品编号	采样深度/m	SiO₂	Al₂O₃	Fe₂O₃	K₂O	Na₂O	CaO	MgO	TiO₂	P₂O₅	MnO	LoI	总和	CO₂
B1	0.3	69.17	17.18	1.48	4.21	4.45	0.93	0.29	0.16	0.05	0.04	1.75	99.72	0.61
B2	0.5	70.05	16.72	1.86	3.92	4.09	0.86	0.26	0.15	0.04	0.07	1.70	99.73	0.23
B3	0.8	70.24	16.50	1.32	4.07	4.81	1.03	0.24	0.16	0.05	0.04	1.29	99.73	0.29
B4	1.1	67.65	17.79	1.98	4.18	5.01	1.00	0.30	0.15	0.05	0.08	1.54	99.71	0.12
B5	1.6	70.32	16.37	1.52	3.99	4.04	0.83	0.19	0.18	0.04	0.04	2.16	99.69	0.40
B6	2.0	71.64	15.61	1.48	3.96	4.16	0.88	0.18	0.13	0.05	0.05	1.55	99.70	0.21
B7	2.9	71.33	15.61	1.86	4.16	3.67	0.69	0.24	0.17	0.06	0.06	1.84	99.71	0.11
B8	3.7	70.97	15.82	1.72	4.06	3.68	0.77	0.24	0.15	0.03	0.05	2.24	99.72	0.26
B9	4.6	72.63	14.71	1.76	3.84	3.90	0.77	0.18	0.14	0.06	0.06	1.67	99.72	0.22
B10	5.4	71.89	15.34	1.69	3.98	3.94	0.77	0.17	0.14	0.06	0.06	1.67	99.70	0.10
B11	6.4	71.70	15.65	1.41	4.26	3.83	0.80	0.15	0.12	0.05	0.05	1.71	99.73	0.09
B12	7	70.77	15.89	1.60	3.86	5.26	1.44	0.16	0.14	0.07	0.06	0.45	99.69	0.09
lg(C_max/C_min)		0.03	0.08	0.18	0.05	0.16	0.32	0.28	0.17	0.31	0.32	0.70		0.84
C1	0.1	78.49	12.38	1.17	3.17	0.10	0.18	0.24	0.13	0.05	0.04	3.87	99.81	0.39
C2	0.6	75.82	14.44	0.95	3.63	0.10	0.16	0.11	0.10	0.06	0.03	4.35	99.76	0.09
C3	1.2	77.16	13.16	1.24	3.31	0.09	0.13	0.14	0.13	0.06	0.03	4.31	99.75	0.14
C4	1.7	77.21	13.18	1.12	3.64	0.12	0.13	0.15	0.14	0.06	0.03	3.96	99.74	0.31
C5	2.4	76.85	13.14	1.75	3.19	0.10	0.12	0.17	0.16	0.07	0.05	4.18	99.78	0.30
C6	3.5	82.93	9.50	1.09	2.84	0.13	0.12	0.14	0.08	0.05	0.03	2.74	99.65	0.30
C7	4.7	74.01	14.66	1.41	4.01	2.03	0.37	0.12	0.13	0.08	0.05	2.86	99.72	0.31
C8	6	70.04	16.20	1.85	3.86	5.08	1.43	0.23	0.19	0.08	0.05	0.62	99.64	0.09
lg(C_max/C_min)		0.07	0.23	0.29	0.15	1.77	1.08	0.34	0.34	0.25	0.29	0.85		0.65

样品编号	采样深度/m	w_B/(μg·g^-1)									w_B/(ng·g^-1)
样品编号	采样深度/m	Nb	Th	U	La	Y	Zr	Sb	Bi	Pb	Au	Ag
B1	0.3	8.5	2.9	0.48	34.7	5.9	115	0.01	0.05	23	1.54	268
B2	0.5	7.4	2.7	0.45	27.9	4.8	104	0.04	0.08	23	2.02	798
B3	0.8	7.8	2.7	0.28	26.0	4.2	86	0.01	0.11	25	3.05	801
B4	1.1	7.7	2.6	0.32	36.8	5.3	101	0.03	0.06	20	5.84	748
B5	1.6	8.2	3.0	0.44	33.5	4.0	96	0.01	0.05	25	1.37	282
B6	2.0	6.5	2.5	0.33	29.1	4.3	88	0.03	0.04	23	0.78	746
B7	2.9	10.1	2.4	0.41	32.9	3.3	83	0.01	0.14	30	2.61	185
B8	3.7	7.5	2.4	0.37	26.7	5.8	78	0.06	0.03	18	1.19	273
B9	4.6	7.7	1.6	0.40	47.1	9.2	57	0.01	0.12	24	0.72	247
B10	5.4	7.9	1.8	0.31	35.1	6.1	64	0.03	0.13	30	0.99	172
B11	6.4	8.1	1.8	0.35	14.9	2.6	67	0.01	0.02	18	0.77	698
B12	7	8.9	2.3	0.40	27.6	4.2	82	0.01	0.12	20	1.10	305
lg(C_max/C_min)		0.19	0.27	0.23	0.50	0.55	0.30	0.78	0.85	0.22	0.91	0.67
C1	0.1	7.0	2.0	0.30	21.6	3.7	62	0.03	0.09	17	0.37	415
C2	0.6	5.2	1.7	0.21	20.3	1.9	54	0.03	0.02	23	0.46	201
C3	1.2	6.0	2.1	0.28	29.4	4.3	71	0.01	0.11	27	0.51	269
C4	1.7	6.4	2.0	0.29	25.2	3.2	70	0.03	0.09	30	0.67	284
C5	2.4	7.6	2.5	0.42	27.2	4.6	68	0.01	0.13	26	0.35	722
C6	3.5	4.6	1.3	0.22	14.2	3.1	47	0.03	0.08	16	7.58	207
C7	4.7	5.4	2.1	0.20	28.5	2.7	54	0.01	0.06	16	0.81	427
C8	6	7.9	2.1	0.38	25.6	3.8	98	0.06	0.16	22	1.09	368
lg(C_max/C_min)		0.23	0.28	0.32	0.32	0.38	0.32	0.78	0.90	0.27	1.34	0.56
检出限		1	0.003	0.01	0.12	0.12	1	0.05	0.05	2	0.1	10