DIWA TYPE OF GOLD MINERALIZATION IN THE YINSHAN-YANSHAN-LIAO-JI ORE BELT,CHINA

DIWA TYPE OF GOLD MINERALIZATIONIN THE YINSHAN-YANSHAN-LIAO-JIORE BELT, CHINAWang Fuquan(Changsha Institute of Geotectonics, Academia Sinica, Changsha, 410013, Hunan, China)Yinshan-Yanshan-Liao-Ji gold ore belt diwa type of gold mineralization, diwa regime, diwa type oftectono-magmatismThis studied gold ore belt is giant and very important in China. Its regional tectonics and evolutional process are complicated. There are a few of view points on its geotec-tonic attribute in the Mesozoic and Cenozoic eras and on the type of its some gold ore deposits, especially, on one hosted in the pre-diwa geological bodies. On the basis of the diwa theory, the author discussed the regionalization, and its evolutional process, and some features of diwa tectono-magmatism and diwa type of gold mineralization in this belt. The author proposed that(1)the main body zone is a part of the diwa regime in the Mesozoic and Cenozoic eras, and(2)the diwa tectono-magmatism had a series of features such as

GEOCHEMICAL REASERCH ON ORE-CONTROLLING STRUCTURE IN LIAODONG LUOQUANBEI-BAIYUN GOLD MINERAL BELT

In recent2 0 years,because of the finding ofmany large- superlargegold deposits,we re- new the theories for prospecting and gain many things and conceptions.The current geo- chemical and gold- forming theories underline the importance of the early submarine volcano- sedimentation,metamorphic differention,sedimentation of terrigenous clastics,thermal spring and it’s sedimentation,syngenesis process and other hypergene supplying the source for metallogenic materials.According to the study for source bed(rock) and depsitional for- mation of gold,we find that gold will be gradually enriched and mineralized in source bed (rock) ,because of variousgeologicprocesses,such as regional metamorphism ormigmatiza- tion,geothermal bittern,volcanism. The ore- control of deep and giant fault and ductile shear beltand tectono- flash space is emphasized,especially,we should notice the long- term, succession and multistage of the

Ore Forming Fluids of Several Gold Deposits in the Irtysh Gold Belt, Xinjiang, China

The metallogenic environment of the Irtysh gold belt in Xinjiang is studied in detail.The metallogenic geological background,metallogenic conditions and ore-controlling factors of the gold deposits in eastern,central and western regions of the metallogenic belt are compared.The metallogenic structure of the Irtysh tectonic belt has the characteristics of diverging to the west and converging to the east.Composite ore controlling by ductile shearing and magmatic activity in Irtysh gold belt result in zoned and segmented distribution of gold mineralization.Through the fluid inclusion research and H-O-S isotope analysis,the evolution regularity of gold ore-forming fluids in the region was analyzed.Synchrotron radiation X-ray fluorescence was used to analysis the concentration of metal elements in a single fluid inclusion,explaining the occurrence and migration process of Au in hydrothermal fluid.The source of ore forming minerals in western gold deposit is more closely related to magmatic activity,and the structural metamorphism of eastern gold deposit has greater influence on mineralization.Metallogenic fluids of gold deposits are characterized by metamorphic water(and magmatic water)in the early stage and mixed with meteoric water in the late stage.And the metallogenic elements are enriched in CO2 rich fluid.The Au is mainly activated,migrated and enriched with the mixed fluid of magmatic hydrothermal,metamorphic hydrothermal and atmospheric precipitation in the medium-low temperature,shallow to medium-deep environment.

The Geology, Fluid Inclusions, and O-S Isotopes of the Mibei Gold Deposit, Hunan Province, Southern China

The Mibei gold deposit,located in the southwestern part of the Xuefengshan uplift zone,the middle section of the Jiangnan orogenic belt in southern China,has estimated gold resources of approximately seven tons.This deposit is primarily a quartz vein-type gold deposit,with ore bodies occurring mainly within Neoproterozoic metasediments.The main metallic minerals in the ore are pyrite,chalcopyrite,and arsenopyrite.In this study,the petrography and microthermometry of ore-forming fluid inclusions,oxygen isotopes of gold-bearing quartz,and sulfur isotopes of goldbearing sulfides and arsenopyrite were analyzed.Three types of fluid inclusions were identified:type Ⅰa three-phase inclusions comprising vapor and two phases of liquids(V_(CO_(2))+L_(CO_(2))+L_(H2O)),type Ⅰb two-phase liquids(L_(CO_(2))+L_(H2O)),typeⅡ two-phase vapor-rich inclusions(V/V+L> 50%),and type Ⅲ pure liquid inclusions.Type Ⅰ inclusions were heated uniformly to the liquid phase,type Ⅱ inclusions were heated uniformly to the gas phase,and type Ⅲ inclusions were heated without change.In general,the temperature range of homogenization to liquid phase of fluid inclusions in the Mibei gold deposit is 204-227℃.The salinity of the inclusion ranges from 4.6 to 12.2 wt% NaCl equiv.The δ~(18)O_(SMOW) of gold-bearing quartz varies from 16.9‰ to 17.5‰.The δ~(18)O_(H2O) of gold-bearing quartz are varied from 6.5‰ to 7.5‰.The δ~(34)S values of gold-bearing pyrite range from 1.7‰ to 6.8‰.The δ~(34)S values of gold-bearing arsenopy rite range from 5.6%o to 5.9‰.Theδ~(34)S values of pyrite from wall rocks slate range from 6.4‰ to 11.6‰.This evidence implies that the ore-forming fluids of the Mibei gold deposit originated from magmatic-hydrothermal processes,mixing with minor S from the surrounding metasediments.Combined with the evolution of the Jiangnan orogenic belt,due to the magmatic and tectonic activities of the Xuefengshan uplift during the Caledonian period,the fault seal mechanism controlled the ore-forming process.Overall,the Mibei gold deposit is more akin to a magmatic-hydrothermal gold deposit.