Fluid Evolution and Mineralization Mechanism of Dongchuan Copper Deposit in Yunnan Province

doi:10.19657/j.geoscience.1000-8527.2021.01.25

Abstract

Abstract:

Dongchuan copper deposit is important sediment-hosted stratiform copper deposits (SSC) in China, which has remarkable multilayered metallogenic characteristics and typical copper sulfide zoning. In this study, the fluid inclusions of copper ore from different layers were analyzed by microthermometry and laser Raman spectrum. The results show that: two types of inclusions are distinguished in the copper ores of Dongchuan Group, which are the light-colored and the dark-colored inclusions. The composition of light-colored inclusions is dominated by H₂O, riching in halite, a small amount of sylvite, and anhydrite crystals, which represents oxidized ore-bearing brine, coming from dissolution of marine evaporate and formation water between strata.Microthermometry analysis shows that the ore-forming brine has the characteristics of low-medium temperature (140-300 ℃), middle-high salinity (12%-44%), and belongs to Na ⁺-K ⁺-Ca ^2--Cl ^-(SO₄ ^2-) basin brine. The dark-colored organic inclusion represents reduced fluid, which comes from the carbonaceous slate of Heishan Formation and the algal organism decomposed Luoxue Formation. Dongchuan copper deposit took the stromatolite-rich sandstone dolomite of Luoxue Formation as the precipitation system, and the carbonaceous slate of Heishan Formation as the barrier layer, forming a fluid closed physicochemical trap. The oxidized ore-bearing brine was transported to the reductive precipitation system through the supply system, and mixed with the reduced fluid and the organic-bearing stratum, and formed the sediment-hosted stratiform and veined copper orebodies.

Key words: Dongchuan copper deposit, fluid inclusion, oxidized ore-bearing brine, reductive fluid, multilayer copper orebody

CLC Number:

P618.41

ZENG Ruiyin, JIANG Hua, ZHU Xinyou, ZHANG Xiong, XIAO Jian, LÜ Xiaoqiang, HU Chuan, YANG Xiaokun, LI Jinlin, ZHEN Zheguang. Fluid Evolution and Mineralization Mechanism of Dongchuan Copper Deposit in Yunnan Province[J]. Geoscience, 2021, 35(01): 244-257.

Figures/Tables 11

References 47

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矿体类型		寄主矿物	均一温度t_h/℃			冰点温度t_m,ice/℃			NaCl子晶熔化温度t_m,s/℃
矿体类型		寄主矿物	范围	均值	FIA/个	范围	FIA/个	盐度/%	范围	FIA/个	盐度/%
桃园式铜矿		Dol	147.5~243.7	191.9	8	-19.4~-7.7	5	11.3~22.0	298.3	1	38.0
		Cal	194.3~219.0	209.6	3
		Q	167.5~251.9	206.5	15	-21.5~-12.0	12	15.9~23.4	230.2~288.6	3	33.5~37.6
		统计	147.5~251.9	202.4	26	-21.5~-7.7	20	11.3~23.4	230.2~298.3	4	33.5~38.0
东川式	层控脉状铜矿体	Dol	197.7~249.0	226.4	12	-21.4~-9.6	8	13.5~23.3	293.1~331.4	5	37.7~41.2
		Q	185.0~275.8	213.8	17	-21.7~-14.8	8	18.5~23.5	268.0~378.3	9	36.1~45.2
		统计	185.0~275.8	222.5	29	-21.7~-9.6	16	13.5~23.5	268.0~378.3	14	36.1~45.2
	层状铜矿体	Dol	168.7~224.2	185.4	6	-20.7~-14.2	5	17.9~22.9	222.5	1	33.1
		Q	133.7~288.6	208.8	25	-20.9~-8.8	19	12.6~23.0	280.1~375.8	3	36.7~44.9
		统计	133.7~288.6	205.6	31	-20.9~-8.8	24	12.6~23.0	222.5~375.8	4	33.1~44.9
稀矿山式铁铜矿体		Dol	170.1~304.3	213.04	10	-22.1~-14.0	8	17.8~23.8	304.8~362.7	2	38.9~43.6
		Cal	191.9~337.4	243.84	10	-21.0~-20.4	2	22.6~23.0	273.1~339.2	8	36.2~41.4
		Q	181.3~357.9	244.44	11	-21.5~-15.3	11	18.9~23.4	291.2	1	37.5
		Ab	190.0~273.0		12	-22.0~-12.0	5	16.0~23.7
		统计	170.1~357.9	234.12	31	-22.1~-12.0	26	16.0~23.8	273.1~362.7	11	36.2~43.6
辉绿岩中的铜矿体		Dol	182.2~256.7	212.8	14	-19.2~-13.4	10	17.2~22.0	351.1	1	42.6
		Q	193.6~293.6	232.6	10	-20.9~-17.5	5	20.7~23.4
		统计	182.2~293.6	220.8	24	-20.9~-13.4	15	17.2~23.4	351.1	1	42.6
角砾岩		Q	188.8~272.4	215.9	9	-14.0~-11.7	4	15.6~17.8	230.0~337.8	5	33.5~41.3

矿体类型		寄主矿物	均一温度t_h/℃			冰点温度t_m,ice/℃			NaCl子晶熔化温度t_m,s/℃
矿体类型		寄主矿物	范围	均值	FIA/个	范围	FIA/个	盐度/%	范围	FIA/个	盐度/%
桃园式铜矿		Dol	147.5~243.7	191.9	8	-19.4~-7.7	5	11.3~22.0	298.3	1	38.0
		Cal	194.3~219.0	209.6	3
		Q	167.5~251.9	206.5	15	-21.5~-12.0	12	15.9~23.4	230.2~288.6	3	33.5~37.6
		统计	147.5~251.9	202.4	26	-21.5~-7.7	20	11.3~23.4	230.2~298.3	4	33.5~38.0
东川式	层控脉状铜矿体	Dol	197.7~249.0	226.4	12	-21.4~-9.6	8	13.5~23.3	293.1~331.4	5	37.7~41.2
		Q	185.0~275.8	213.8	17	-21.7~-14.8	8	18.5~23.5	268.0~378.3	9	36.1~45.2
		统计	185.0~275.8	222.5	29	-21.7~-9.6	16	13.5~23.5	268.0~378.3	14	36.1~45.2
	层状铜矿体	Dol	168.7~224.2	185.4	6	-20.7~-14.2	5	17.9~22.9	222.5	1	33.1
		Q	133.7~288.6	208.8	25	-20.9~-8.8	19	12.6~23.0	280.1~375.8	3	36.7~44.9
		统计	133.7~288.6	205.6	31	-20.9~-8.8	24	12.6~23.0	222.5~375.8	4	33.1~44.9
稀矿山式铁铜矿体		Dol	170.1~304.3	213.04	10	-22.1~-14.0	8	17.8~23.8	304.8~362.7	2	38.9~43.6
		Cal	191.9~337.4	243.84	10	-21.0~-20.4	2	22.6~23.0	273.1~339.2	8	36.2~41.4
		Q	181.3~357.9	244.44	11	-21.5~-15.3	11	18.9~23.4	291.2	1	37.5
		Ab	190.0~273.0		12	-22.0~-12.0	5	16.0~23.7
		统计	170.1~357.9	234.12	31	-22.1~-12.0	26	16.0~23.8	273.1~362.7	11	36.2~43.6
辉绿岩中的铜矿体		Dol	182.2~256.7	212.8	14	-19.2~-13.4	10	17.2~22.0	351.1	1	42.6
		Q	193.6~293.6	232.6	10	-20.9~-17.5	5	20.7~23.4
		统计	182.2~293.6	220.8	24	-20.9~-13.4	15	17.2~23.4	351.1	1	42.6
角砾岩		Q	188.8~272.4	215.9	9	-14.0~-11.7	4	15.6~17.8	230.0~337.8	5	33.5~41.3

矿脉类型	样号	寄主矿物	均一温度t_h/℃			冰点温度t_m,ice/℃			NaCl子晶熔化温度t_m,s/℃
矿脉类型	样号	寄主矿物	范围	均值	FIA/个	范围	FIA/个	盐度/%	范围	FIA/个	盐度/%
顺层细矿脉	DC10-2	Dol	159.0~224.2	185.4	5	-20.7~-14.2	4	17.9~22.9	222.5	1	33.1
	DC1937-1	Q	133.7~240.9	187.4	7	-14.4~-8.8	4	12.6~18.1	344.3~375.8	2	41.9~44.9
	DC66C-1	Q	165.3~242.7	197.5	8	-20.8~-12.8	7	16.7~22.9
	统计		133.7~242.7	192.4	20	-20.8~-8.8	15	12.6~22.9	222.5~375.8	3	33.1~44.9
高角度含矿脉	DC1937-1	Q	188.2~288.6	233.6	10	-17.5~-9.8	7	13.1~20.6	280.1~302.9	2	36.7~38.4
	DC1919-3	Q	180.9~246.6	202.7	6	-20.9~-14.2	6	18.0~23.0
	统计		180.9~288.6	222.0	16	-20.9~-9.8	13	13.7~23.0	280.1~302.9	2	36.7~38.4

矿脉类型	样号	寄主矿物	均一温度t_h/℃			冰点温度t_m,ice/℃			NaCl子晶熔化温度t_m,s/℃
矿脉类型	样号	寄主矿物	范围	均值	FIA/个	范围	FIA/个	盐度/%	范围	FIA/个	盐度/%
顺层细矿脉	DC10-2	Dol	159.0~224.2	185.4	5	-20.7~-14.2	4	17.9~22.9	222.5	1	33.1
	DC1937-1	Q	133.7~240.9	187.4	7	-14.4~-8.8	4	12.6~18.1	344.3~375.8	2	41.9~44.9
	DC66C-1	Q	165.3~242.7	197.5	8	-20.8~-12.8	7	16.7~22.9
	统计		133.7~242.7	192.4	20	-20.8~-8.8	15	12.6~22.9	222.5~375.8	3	33.1~44.9
高角度含矿脉	DC1937-1	Q	188.2~288.6	233.6	10	-17.5~-9.8	7	13.1~20.6	280.1~302.9	2	36.7~38.4
	DC1919-3	Q	180.9~246.6	202.7	6	-20.9~-14.2	6	18.0~23.0
	统计		180.9~288.6	222.0	16	-20.9~-9.8	13	13.7~23.0	280.1~302.9	2	36.7~38.4