Characteristics and genesis of Lalongla MVT-like deposit in Changdu;region, Tibet

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	Characteristics and genesis of Lalongla MVT-like deposit in Changdu;region, Tibet
	Liu YingChao 5; Hou ZengQian ; Yu YuShuai 1; Tian ShiHong 2; Li YuLong 3; Yang ZhuSen 2
刊名	ACTA PETROLOGICA SINICA
	2013
卷号	29 期号:4 页码:1407-1426
关键词	MVT-like Pb-Zn deposit Lalongla type Pb-Zn deposit Characteristics Genesis Changdu Tibet
ISSN号	1000-0569
英文摘要	Changdu region, located in the northeastern margin of Tibetan collisional orogenic belt, is the important part of Southwest 'Sanjiang' metallogenic belt. Carbonate-hosted Pb-Zn deposits controlled by thrust nappe structures are abundant and with plenty reserves in this region. Lalongla deposit is located in the southwest of the most famous carbonate-hosted Pb-Zn ore concentration area in Changdu region and is a typical representative. The Pb-Zn mineralization of Lalongla deposit is born in the hanging wall of a thrust fault and ore bodies, mainly produced as lens, distribute along a facies transition between mud shale in Jiapeila Formation and limestone in Bolila Formation in Late Triassic. Breccia and mesh-vein are main ore structures and galena, sphalerite and smithsonite are main ore minerals. The ore-control factor and ore occurrence in this deposit represent a new carbonate-hosted deposit type in 'Sanjiang' metallogenic belt and then it is named as Lalongla type. The main ore-forming process in this deposit can be divided into Period I (shortened form of sulfide period) and Period II (shortened form of sulfide-carbonate period), between which a compressing deformation occurred. Two kinds of fluid inclusion including LV inclusion rich in liquid and LV inclusion rich in CO2 and CH4 occur in Period I. A microthermal testing work suggests two kinds of hydrothermal fluids in this period, which are with low temperature (130 similar to 140 degrees C), high salinity (23% similar to 24% NaCleqv) and middle to high density (1. 10 similar to 1. 12g . cm(-3)) nature and with middle to low temperature (170 similar to 180 degrees C), high salinity (23% similar to 24% NaCleqv) and middle to low density (1. 06 similar to 1. 08g . cm(-3)) nature, respectively. For the two periods, the liquid parts of hydrothermal fluids both belong to Ca2+-Mg2+-Na+-K+-SO42--Cl--F--NO3- system and the ion contents, H-O isotope composition (-137 parts per thousand similar to -110 parts per thousand for delta DV-SMOW and -2. 92 parts per thousand similar to 13. 42 parts per thousand for delta O-18(V-SMOW)), C-O isotope composition of calcite (0. 9 parts per thousand similar to 7. 2 parts per thousand for delta(13) CV-PDB and 9. 1 parts per thousand similar to 26. 5 parts per thousand for delta(18) OV-SMOW) are all similar to each other, suggesting two resources, including low-temperature, high salinity basin brine and middle-temperature, high-salinity regional fluid composed by evaporated-concentrated seawater cocooned in strata, metamorphic water released by metamorphic rock and the meteoric water, for the hydrothermal fluids. The sulfur isotope composition for the two Periods is still similar. The delta(34) S values of sulfide are negative (-24. 7 parts per thousand similar to -11. 5 parts per thousand), of barite are positive (11. 3 parts per thousand similar to 22. 9 parts per thousand) and of gypsum (2. 0 parts per thousand similar to 4. 7 parts per thousand) are between the two former, suggesting reducing S comes from biological sulfate reduction which derives from the basinal brine descending from overlying Paleogene basin and evaporated-concentrated seawater cocooned in strata, and mixing of two kinds of fluid, which are local fluid rich in reducing sulfur and regional fluid rich in metal, causes the deposition of mineralized minerals.;The Pb isotope composition of galena in the two periods are nearly the same and the ranges of Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 are 18. 8646 similar to 18. 8835, 15. 6619 similar to 15. 6677 and 38. 9404 similar to 38. 9796, respectively, proving that Pb isotope comes from metamorphic basement and limestone ( and elastic rock) caprock distributed in the orogenic belt. By comparing Lalongla deposit with carbonate-hosted deposits in Sanjiang' belt, the authors finally point out that Lalongla deposit could be classified as MVT-like deposit controlled by thrust nappe and its moralization model can be explained as followings; Structural trap formes in the carbonate formation due to thrust nappe. The basinal brine in Paleogene basin descends, accumulates, and generates the local fluid reservoir rich in H2S accompanied by the biological sulfate reduction. Regional fluid released by the compression deformation migrates along the main detachment zone of thrust nappe, leachs ore-forming minerals in strata and generates allochthonous fluid rich in metallic elements. Along extended faults by final stretch of local thrust faults regional fluid ascends to the interface between limestone and mud shale, the favorable space, mixes with local fluid and leads to the uninstall mineralization of metal materials and the lens ore-bodies along the facies transition between different rocks finally form.
学科主题	矿床地质
WOS关键词	ZINC ORE-DEPOSIT ; FLU##ID#INCLUSION ; YUSHU AREA ; ISOTOPE ; ORIGIN ; OXYGEN ; CHINA ; EVOLUTION ; BRINES ; METALLOGENESIS
WOS研究方向	Geology
语种	中文
出版者	SCIENCE PRESS
WOS记录号	WOS:000318260300024
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/40175]
专题	中国地质调查局武汉地质调查中心
作者单位	1.CAGS, Inst Geol, Beijing 100037, Peoples R China. 2.Wuhan Inst Geol & Mineral Resources, Wuhan 430205, Peoples R China. 3.CAGS, Inst Mineral Resources, Beijing 100037, Peoples R China. 4.Qinghai Inst Geol Survey, Xining 810012, Peoples R China. 5.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Liu YingChao,Hou ZengQian,Yu YuShuai,et al. Characteristics and genesis of Lalongla MVT-like deposit in Changdu;region, Tibet[J]. ACTA PETROLOGICA SINICA,2013,29(4):1407-1426.
APA	Liu YingChao,Hou ZengQian,Yu YuShuai,Tian ShiHong,Li YuLong,&Yang ZhuSen.(2013).Characteristics and genesis of Lalongla MVT-like deposit in Changdu;region, Tibet.ACTA PETROLOGICA SINICA,29(4),1407-1426.
MLA	Liu YingChao,et al."Characteristics and genesis of Lalongla MVT-like deposit in Changdu;region, Tibet".ACTA PETROLOGICA SINICA 29.4(2013):1407-1426.