Hydrothermal Fluid Origins of Carbonate-Hosted Pb-Zn Deposits of the Sanjiang Thrust Belt, Tibet：Indications from Noble Gases and Halogens

Research Article| August 01, 2017 Hydrothermal Fluid Origins of Carbonate-Hosted Pb-Zn Deposits of the Sanjiang Thrust Belt, Tibet: Indications from Noble Gases and Halogens Ying-Chao Liu; Ying-Chao Liu † 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China †Corresponding author: e-mail, lychappy@126.com Search for other works by this author on: GSW Google Scholar Mark A. Kendrick; Mark A. Kendrick 2Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Search for other works by this author on: GSW Google Scholar Zeng-Qian Hou; Zeng-Qian Hou 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Zhu-Sen Yang; Zhu-Sen Yang 3Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Shi-Hong Tian; Shi-Hong Tian 3Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Yu-Cai Song; Yu-Cai Song 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Masahiko Honda Masahiko Honda 2Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Ying-Chao Liu † 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China Mark A. Kendrick 2Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Zeng-Qian Hou 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China Zhu-Sen Yang 3Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100083, China Shi-Hong Tian 3Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100083, China Yu-Cai Song 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100083, China Masahiko Honda 2Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia †Corresponding author: e-mail, lychappy@126.com Publisher: Society of Economic Geologists First Online: 24 May 2017 Online Issn: 1554-0774 Print Issn: 0361-0128 © 2017 Society of Economic Geologists.Society of Economic Geologists Economic Geology (2017) 112 (5): 1247–1268. https://doi.org/10.5382/econgeo.2017.4509 Article history First Online: 24 May 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ying-Chao Liu, Mark A. Kendrick, Zeng-Qian Hou, Zhu-Sen Yang, Shi-Hong Tian, Yu-Cai Song, Masahiko Honda; Hydrothermal Fluid Origins of Carbonate-Hosted Pb-Zn Deposits of the Sanjiang Thrust Belt, Tibet: Indications from Noble Gases and Halogens. Economic Geology 2017;; 112 (5): 1247–1268. doi: https://doi.org/10.5382/econgeo.2017.4509 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The Sanjiang metallogenic belt includes a variety of economically important carbonate-hosted Pb-Zn deposits that share some similarities with classic Mississippi Valley-type (MVT) ore deposits but are hosted within a thrust belt rather than an orogenic foreland. This study aims to clarify the origin of mineralizing fluids responsible for this style of mineralization.Fluid inclusions trapped in ore-stage carbonate and fluorite from these deposits have salinities of ~6 to 28 wt % NaCl equiv and homogenization temperatures of 70° to 370°C that extend to much higher values than are typical of MVT deposits. The majority of ore-stage samples have fluid inclusion molar Br/Cl ratios of between seawater (1.5 × l0−3) and (2.86 ± 0.04) × 10−3, but low-salinity fluid inclusions in late calcite have lower Br/Cl of less than (0.55 ± 0.01) × 10−3. In contrast, fluid inclusion molar I/Cl ratios are uniformly greater than the seawater value of ~ 0.8 × 10−6 and extend from (2.1 ± 1.1) × 10−6 to (506 ± 12) × 10−6. This range of Br/Cl and I/Cl values is similar to what has been reported for fluid inclusions in other MVT districts and together with the fluid salinity implies the ore-forming fluids had a dominant origin from basinal brines (e.g., sedimentary formation waters) formed by the subaerial evaporation of seawater; all the fluids were influenced by addition of organic Br and I derived from the sedimentary host rocks and some fluids were locally modified by interaction with evaporites producing low Br/Cl ratios.The fluid inclusions have 40Ar/36Ar ratios of up to 441 that are higher than the atmospheric value of 296 and typical of carbonate sedimentary rocks. The fluid inclusions have high concentrations of atmospheric 36Ar and variable 129Xe/36Ar and 84Kr/36Ar ratios that are outside the range expected from mixing air and air-saturated water. These data are likely to reflect a complex fluid history involving acquisition of atmospheric (36Ar, 84Kr,129Xe) and radiogenic (e.g., 40Ar*) noble gases trapped in sedimentary rocks and fractionation of these gases between water and hydrocarbons. The 3He/4He ratios of fluorite fluid inclusions range from a typical crustal value of 0.061 ± 0.004 to values of >0.7 Ra, indicating a minor component of mantle-derived 3He. The fluids with the highest 3He/4He also have 4He/40Ar* close to the mantle value, suggesting the 3He could have been introduced by a volumetrically minor fluid of either magmatic or deep metamorphic origin (40Ar* = radiogenic 40Ar).The new halogen and noble gas data are consistent with a model in which regional Pb-Zn mineralization formed by mixing two modified basinal brines that were transported through independent aquifers and fluid pathways to the sites of mineralization. A low-temperature brine contained organic Br, I, and H2S, and a high-temperature metal-rich brine (>370°C) that included a volumetrically minor magmato-metamorphic component was channeled up deeply penetrating thrust structures. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.