Giant Mineral Deposits and Their Geodynamic Setting in the Lanping Basin, Yunnan, China

There are giant mineral deposits, including the Jinding Zn-Pb and Baiyangping Ag-Co-Cu, and otherimportant mineral deposits (e.g., Baiyangchang Ag-Cu, Jinman Cu deposits, etc.) in the Lanping Mesozoic-Cenozoic Basin, Yunnan Province, China. The tabular ore-bodies and some veins hosted in terrestrial clastic rocks of the Mesozoic-Cenozoic age and no outcropping of igneous rocks in the giant deposits lead to the proposal of syngenetic origin, but the giant mineral deposits are not stratabound (e.g. MVT, sandstone- and Sedex-type). They formed in a continental red basin with intense crust movement. The mineralization is controlled by structures and lithology and occurs in different strata, and no sedimentary nature and no exhalative sediments are identified in the deposits. The deposits show some relations with organic matter (now asphalt and petroleum) and evaporates (gypsum). The middle-low-temperature (mainly 110℃ to 280℃) mineralization took place at a depth of about 0.9 km to 3.1 km during the early Himalayan (58 to 67 Ma). The salinity of ore-forming fluids is surprisingly low (1.6% to 18.0 wt% (NaCl)eq). Affected by the collision of the Indian and Eurasian plates, the mantle is disturbed under the Lanping Basin. The large-scale mineralization is closely linked with the geodynamics of the crust movement, the mantle and mantle-flux upwelling and igneous activity. Giant mineral deposits and their geodynamic setting are unique in the Lanping Basin.

Metallogeny of the Baiyangping Lead-Zinc Polymetallic Ore Concentration Area, Northern Lanping Basin of Yunnan Province, China

The Lanping Basin in the Nujiang-Lancangjiang-Jinshajiang （the Sanjiang） area of northeastern margin of the Tibetan Plateau is an important part of eastern Tethyan metallogenic domain. This basin hosts a number of large unique sediment-hosted Pb-Zn polymetallic deposits or ore districts, such as the Baiyangping ore concentration area which is one of the representative ore district. The Baiyangping ore concentration area can be divided into the east and west ore belts, which were formed in a folded tectogene of the India-Asia continental coUisional setting and was controlled by a large reverse fault. Field observations reveal that the Mesozoic and Cenozoic sedimentary strata were outcropped in the mining area, and that the orebodies are obviously controlled by faults and hosted in sandstone and carbonate rocks. However, the oreforming elements in the east ore belt are mainly Pb-Zn -Sr-Ag, while Pb-Zn-Ag-Cu-Co elements are dominant in the west ore belt. Comparative analysis of the C-O-Sr-S-Pb isotopic compositions suggest that both ore belts had a homogeneous carbon source, and the carbon in hydrothermal calcite is derived from the dissolution of carbonate rock strata; the ore- forming fluids were originated from formation water and precipitate water, which belonged to basin brine fluid system; sulfur was from organic thermal chemical sulfate reduction and biological sulfate reduction; the metal mineralization material was from sedimentary strata and basement, but the difference of the material source of the basement and the strata and the superimposed mineralization of the west ore belt resulted in the difference of metallogenic elements between the eastern and western metallogenic belts. The Pb-Zn mineralization age of both ore belts was contemporary and formed in the same metaliogenetic event. Both thrust formed at the same time and occurred at the Early Oligocene, which is consistent with the age constrained by field geological relationship.

A Preliminary Study on Fluid Inclusions and Mineralization of Xitieshan Sedimentary-Exhalative (SEDEX) Lead-Zinc Deposit

The Xitieshan lead-zinc deposit is located at the northern margin of the Qaidam Basin, Qinghai Province, China, and had developed a complete marine sedimentary-exhalative system. Our preliminary study of ore-forming fluids shows that fluid inclusions in quartz from altered stockwork rocks that represent the pipe facies have a wide range of temperature and salinity. The intense fluid activities are characteristics of the pipe facies of the exhalative system. Fluid inclusions in carbonates near the unstratified ore bodies hosted in the thick-bedded marble which represents vent-proximal facies are large in size and have moderate to high temperatures. They represent unerupted sub-seafloor fluid activity. Fluids in altered stockwork rocks and carbonates have similar H20-NaCI-CO2 system, both belonging to the sedimentary-exhalative system. The fluids migrate from the pipe facies to the unstratified ore bodies. Boiling of the fluids causes the separation of CO2 vapor and liquid H2O. When the fluids migrate into the unconsolidated thick-bedded marble, the escape of CO2, decreasing temperature and pressure as well as some involvement of seawater into the fluids result in the unmixing of fluids with high and low salinity and deposition of ore-forming materials. The two unmixed fluids were trapped in unconsolidated carbonates and the ore-forming materials were deposited in the unconsolidated carbonates to form the sedimentary-exhalative type unstratified ore bodies. The oreforming temperature of unstratified ore bodies is up to high temperature indicating that there is a huge ore-forming potential in its deep.

Zinc, copper, and strontium isotopic variability in the Baiyangping Cu–Pb–Zn–Ag polymetallic ore field, Lanping Basin, Southwest China

The Baiyangping Cu-Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt,between the Jinshajiang-Ailaoshan and Lancangjiang faults,and the deposit can be divided into eastern and western ore zones.Based upon microscope observation of ore minerals and analysis of zinc,copper,and strontium isotope composition,we conclude that:(1)the zinc isotopic compositions of sphalerite from the eastern and western ore belt of the Baiyangping polymetallic ore deposits are enriched in both the heavy(-0.09‰ to+0.15‰) and light(-0.19‰ to-0.01‰)zinc isotopes.Rayleigh fractionation is likely the additional factor controlling the observed temporal and spatial variations in zinc isotopes in the two studied ore zones.The zinc isotopic composition in the Baiyangping polymetallic Pb-Zn deposits may have the same fractionation as that of magmatic-hydrothermal,VHMS,SEDEX,and MVT deposits,as demonstrated by geological and other geochemical evidence;(2) the range of δ^(65)Cu in massive tetrahedrite is from-0.06‰ to+0.12 ‰ that relates to the early stages of ore-formation,which are higher than that of venial chalcopyrite(from-0.72‰ to-0.07‰)formed at a late ore-forming stage in the western ore belt.Different ore-forming stages and alteration or leaching processes are likely the main factors controlling the observed variations in copper isotopes in the western ore zone;(3) the ^(87)Sr/^(86)Sr value of hydrothermal calcite in eastern(0.7080-0.7093) and western(0.7085-0.7113) ore belt suggested that mineralization of early calcite,with^(87)Sr/^(86)Sr values much higher than in ancient Late Triassic seawater,may be related to recrystallization from a radiogenic Sr-rich or silicifying fluid,either from the strata that the ore-forming fluid flows through or from other fluids.

LA-ICP-MS zircon U-Pb age of rhyolitic lithic-crystal tuffs in Erdaohezi lead-zinc deposit,Inner Mongolia

Erdaohezi lead-zinc deposit belongs to the Derbugan metallogenic belt lying on the northwestern Hailaer-Genhe Mesozoic volcanic basin, located on the western slope of the Da Hinggan Mountains. The deposit is considered as one of the hypabyssal low-temprature hydrothermal lead-zinc deposits associated with volca- nism. In order to lay the foundation on studying its diagenesis and mineralization ages, the detailed studies were carried out by dating the host rocks （i. e. rhyolitic lithic-crystal tufts） using zircon LA-ICP-MS U-Pb method. The dating results show three groups ot! ages. The first group is the captured zircons （the weighted mean ^206pb/238U age as 175.6± 2.3 Ma, MSWD = 0.70, n = 3）. The second group can be regarded as the rock- forming age （the weighted mean ^206pb/238U age as 165.3± 1.9 Ma, MSWD = 2.40, n = 14）. The third group should represent the late stage of the magmatic evolution （the weighted mean ^206pb/238U age as 161.0 ± 3.1 Ma, MSWD = 0.86, n = 4）. According to the ages and the crystal form or CL image characteristics of zircons, it is determined that the diagenesis occurred in the late Middle Jurassic. Based on the regional geology and geo- chronological research, the acidic pyroclastic rocks are space accompaniment and time connection with the Tamu- langou Formation intermediate-mafic volcanic rocks. Both of them constitute the host rocks of the deposit together. The rock combination also provides favorable conditions for large-scale silver, lead and zinc mineralization in this area.

Application of Tectono Geochemical Study in Deep Concealed Ore Body Exploration--As the Huize Super-Large Lead-Zinc Deposit an exemple

1 Geological Background of Minerlization or Geologic Setting The northeast of Yunnan1 Pb-Zn-Ag-Ge polymetallic ore district is an important part of the southwestern margin of the Yangtze block Sichuan-Yunnan-Guizhou

Geochronology and geochemistry of the ore-bearing intrusion in the Longgen Lead-Zinc deposit in Tibet and its geological significance

1 Introduction The Longgen Lead-Zinc deposit is located in the southern Gangdise-Nyainqentantanglha plate and belongs to the western section of the Nyainqentantanglha copper-lead-zinc-silver metallogenic belt.In this paper,

Ore-controlling Regularitiesof Structureinthe Lehong Lead-zinc Deposit, Northeastern Yunnan

1 Introduction The Lehonglead-zincdeposit is a large-sized Pb-Zn depositnewly found in recent years in the Sichuan-Yunnan-Guizhou Lead-zinc Poly-metallic Mineralization Area,which occurrenceis strictly

“Structure-Lithologic-Fluid” Metallogenic Coupling of the Wuzhishan Lead-Zinc Deposit in Puding, Guizhou Province

1 Introduction The Wuzhishan lead-zinc ore-concentrated area in Puding is located in the east of the Sichuan,Guizhou and Yunnan lead-zinc metallogenic domain,with the Youjiang-Nanpan River metallogenic province to the

Spectroscopic Features and Formation Conditions of Sphalerite in the Lead-Zinc Deposit, Guangdong,China

Electron paramagnetic resonance spectra, absorption spectra, cathodoluminescence spectra and infrared spectra of sphalerite from the Lechang remoulded sedimentary lead-zinc deposit have been studied so as to provide microscopic evidence for the formation conditions and mineralization stages of the deposit as well as the geochemical processes of mineralization. On the basis of thermodynamic calculations, the stable fields of sphalerite from different mineralization stages were determined and are shown in logfs_2-logfo_2 diagrams; furthermore. the physico-chemical conditions of mineralization and the properties of mineralization solutions are discussed so that reliability of the genetic information provided by the spectroscopy of sphalerite may also be verified. It is suggested that the temperature and pH value of the mineralization system decrease, and so do the fugacities of O_2, S_2, H_2. and H_2S and the activities of HS^- and SO_4^(2-) from the early to late stages of minerahzation.

Metallogenic Prediction of the Peripheral Areas of the Xiyi Concealed Lead-Zinc Deposit in Baoshan City, Yunnan Province

The newly-discovered Xiyi lead-zinc deposit is a large deposit located in the north central Baoshan block of the southern Sanjiang metallogenic belt section, Southwest China.The surface of the deposit is mainly covered by eluvial-deluvial lateritic layer, without any mineralized outcrops. The main concealed orebody V3 is buffed in the depth of 300-500m. The orebodies are controlled by certain stratigraphic horizons, and most are cut by strata with a high angle, while a few occur along the strata. The direct wall rocks are calcisiltite, calclithite, bioclastic calcarenite,

New Zircon U-Pb Age of Devonian Granites in the Niukutou Lead-Zinc Deposit, Qinghai Province and its Significance for Prospecting Blind Orebodies

Object The Eastern Kunlun Orogen(EKO), An important part of the Tethyan orogenic belt in the northern margin of the Qinghai–Tibet Plateau(Li et al., 2014; Ren Haidong et al., 2016), is a key area for geological research and mineral exploration(Li Bile et al., 2015). The Qimantag Mountain is located in middle segment of the EKO, which has experienced the Early Paleozoic and Late Paleozoic–Early

LAWS GOVERNING THE DISTRIBUTION OF LEAD-ZINC DEPOSITS IN CHINA

An attempt is made in this paper to describe the following laws governing the distribution of lead-zinc deposits in China: spatial distribution laws, temporal distribution laws, deep level control laws, and deposits association and zoning laws.

Experiment and Achievement Enlightenment of Integrated Prospecting of Carbonate-Type Lead-Zinc Deposits in the Sichuan-Yunnan-Guizhou Region of China

Mississippi-Valley＇s carbonate-type （MVT） lead-zinc deposits are the most important type of lead-zinc deposits in the southwest of China. In 2013, China Geological Survey Bureau deployed a project named ＂Experimental Investigation of Integrated Prospecting Technology for Concealed Carbonate-Type Lead-Zinc Deposits in the Region of Sichuan, Yunnan and Guizhou Provinces＂. This project has been implemented by the Chengdu Center of China Geological Survey since 2013, and the project has run for 3 years. The general objective of this project is to establish an effective and adaptable integrated prospecting methodology （including geological, geophysical and geochemical techniques） in search for deep concealed lead-zinc deposits.

滇西兰坪金顶超大型铅锌矿床围岩微量元素地球化学特征及其意义

滇西兰坪盆地是三江成矿带的重要组成部分,金顶铅锌矿是区内重要的超大型矿床。为了查明金顶超大型铅锌矿床的成矿物质来源,对金顶矿区围岩样品进行微量元素地球化学分析。结果显示,稀土总量接近大陆上地壳的平均稀土元素总量值,轻稀土元素相对富集、重稀土元素相对亏损,呈明显的右倾型,具有显著的Eu负异常。微量元素特征显示Cu的平均含量为24.4×10^(-6),未发生明显富集迁移。Pb、Zn平均含量随矿体距离远近变化较大(Pb含量为2.9×10^(-6)~24.7×10^(-6),平均含量为13.1×10^(-6);Zn含量为8.8×10^(-6)~236.0×10^(-6),平均含量为76.6×10^(-6)),与矿体距离呈现出明显的相关性,距离矿体越近,含量越高。稀土元素特征及微量元素相关关系分析表明,矿区围岩古近纪云龙组地层不是提供成矿物质的矿源层。矿区石膏锶、硫同位素地球化学性质显示金顶矿区的石膏为晚三叠世三合洞组蒸发沉积型,且在适当的成矿温度条件下(150~300℃),石膏会发生热化学还原作用(TSR),为金属硫化物矿床提供硫源。

云南兰坪县河西锶矿床地质特征及成矿条件

兰坪县河西锶矿区含矿岩性为一套碳酸盐岩,矿体主要受断裂控制。通过半封闭还原法分析SrSO_(4)含量93.37ω%。形成于干旱气候的开阔海相沉积环境。通过硫同位素测定,锶来源于石钟山组内,后经热液改造富集成矿,矿床类型属沉积-热液型矿床。

Isotopic Compositions of Sulfur in the Jinshachang Lead–Zinc Deposit, Yunnan, China, and its Implication on the Formation of Sulfur-Bearing Minerals

The Jinshachang lead-zinc deposit is mainly hosted in the Upper Neoproterozoic carbonate rocks of the Dengying Group and located in the Sichuan-Yunnan-Guizhou （SYG） Pb-Zn-Ag multi- metal mineralization area in China. Sulfides minerals including sphalerite, galena and pyrite postdate or coprecipitate with gangue mainly consisting of fluorite, quartz, and barite, making this deposit distinct from most lead-zinc deposits in the SYG. This deposit is controlled by tectonic structures, and most mineralization is located along or near faults zones. Emeishan basalts near the ore district might have contributed to the formation of orebodies. The j34S values of sphalerite, galena, pyrite and barite were estimated to be 3.6‰-13.4‰, 3.7‰-9.0‰, -6.4‰ to 29.2‰ and 32.1‰34.7‰, respectively. In view of the similar δ34S values of barite and sulfates being from the Cambrian strata, the sulfur of barite was likely derived from the Cambrian strata. The homogenization temperatures （T ≈ 134--383℃） of fluid inclusions were not suitable for reducing bacteria, therefore, the bacterial sulfate reduction could not have been an efficient path to generate reduced sulfur in this district. Although thermochemical sulfate reduction process had contributed to the production of reduced sulfur, it was not the main mechanism. Considering other aspects, it can be suggested that sulfur of sulfides should have been derived from magmatic activities. The δ34S values of sphalerite were found to be higher than those of coexisting galena. The equilibrium temperatures calculated by using the sulfur isotopic composition of mineral pairs matched well with the homogenization temperature of fluid inclusions, suggesting that the sulfur isotopic composition in ore-forming fluids had reached a partial equilibrium.

An experimental study on metal precipitation driven by fluid mixing: implications for genesis of carbonate-hosted lead–zinc ore deposits

A type of carbonate-hosted lead–zinc(Pb–Zn)ore deposits, known as Mississippi Valley Type(MVT)deposits, constitutes an important category of lead–zinc ore deposits. Previous studies proposed a fluid-mixing model to account for metal precipitation mechanism of the MVT ore deposits, in which fluids with metal-chloride complexes happen to mix with fluids with reduced sulfur, producing metal sulfide deposition. In this hypothesis, however, the detailed chemical kinetic process of mixing reactions, and especially the controlling factors on the metal precipitation are not yet clearly stated. In this paper, a series of mixing experiments under ambient temperature and pressure conditions were conducted to simulate the fluid mixing process, by titrating the metal-chloride solutions, doping withor without dolomite, and using NaHS solution. Experimental results, combined with the thermodynamic calculations, suggest that H_2S, rather than HS^-or S^(2-),dominated the reactions of Pb and/or Zn precipitation during the fluid mixing process, in which metal precipitation was influenced by the stability of metal complexes and the pH. Given the constant concentrations of metal and total S in fluids, the pH was a primary factor controlling the Pb and/or Zn metal precipitation. This is because neutralizing or neutralized processes for the ore-forming fluids can cause instabilities of Pb and/or Zn chloride complexes and re-distribution of sulfur species, and thus can facilitate the hydrolysis of Pb and Zn ions and precipitation of sulfides. Therefore, a weakly acidic to neutral fluid environment is most favorable for the precipitation of Pb and Zn sulfides associated with the carbonate-hosted Pb–Zn deposits.