| The Changpingzi-Wuliping Pb-Zn deposit,located on SW side of northwest Guizhou Yadu-Mangdong fault zone,is a representative deposit related to tectonic-fluid mineralization.Previous work has provided abundant data for the study of this area,but there are still many problems in the study of structural ore-controlling mechanism and metallogenic mechanism.Therefore,on the geological characteristics of the deposit,this paper takes the idea of structural-fluid-mineralization system as the guide,takes ore-controlling structure as the main line,and applies theories and methods of ore field geomechanics,fluid geochemistry,isotope geochemistry,etc.,to carry out the fine anatomy of the deposit,analysis of ore-controlling structure,mineralization process and comparative study of the deposit,and then determines the structural ore-controlling mechanism and mineralization mechanism,and provide a metallogenic model in this paper.The main achievements achieved are as follows:（1）This study is based on the geological characteristics of the deposit,which find out the spatial characteristic of ore-bodies,and determine the metallogenic periods of the deposit.The ore body is located in the carbonate rocks,and controlled by faults,as veins,lenticular output.The main ore minerals in the ore include galena,sphalerite and pyrite,the gangue minerals are mainly calcite,and there is molybdenite in the secondary minerals.This deposit mainly formed in hydrothermal metallogenic period.（2）Analyze and divide the tectonic stages of the mining area,determine the metallogenic structural system and construct the structural ore-controlling model.The tectonic activity in this area is intense,folds and faults are developed,and the main structure is NW-trending,followed by EW and NE-trending.Structures controlled the formation and distribution of ore bodies,and showed obvious characteristics of ore-controlling by grades.Different grades of ore-forming structures controlled the spatial distribution of ore belts,ore fields and deposits（bodies）respectively,and formed ore-guiding,ore-distributing and ore-hosting structures in the region.There are three tectonic systems developed in this area,namely,forming NE structural belt,EW structural belt and SN structural belt in turn.The superposition of these three tectonic events constitutes a fault-fold structural combination with NW faults as the main component in space.The NE structural belt formed is a metallogenic structural system,which formed in the late Indosinian period to Yanshanian period,and controls the"layer-vein"mineralization pattern by a"ru-type"structure.（3）This study found out the nature of ore-forming fluid and the source of ore-forming materials,and determined the mechanism of ore migration and precipitation.The characteristics of fluid inclusions show that the ore-forming fluid has undergone a transformation process from medium temperature and low salinity to medium low temperature and low salinity to low temperature and medium salinity.The liquid part of ore forming fluid belongs to Ca2+-Mg2+-Cl--SO42-system,which is similar to basin brine.The characteristics of REE-C-H-O-He-Ar-Pb isotopes show that the ore-forming fluid is multi-sourced,mainly from the basement strata,followed by the underlying cap rocks,which migrate in the form of Cl-complexes.The hydrothermal fluid is a mixed fluid composed of deep fluid containing lead and zinc and basin brine heated by atmospheric precipitation,which is supplemented by a large amount of atmospheric precipitation in the later period.S isotopic characteristics show that S mainly comes from TSR of marine sulfate in ore-bearing strata,and partly through SOD of organic matter.The mixing of deep hot fluid and shallow fluid is an important mechanism of mineral precipitation.（4）This study reveals that structure is the dominant controlling factor of deposit formation,clarifies the mechanism of lead-zinc mineralization,determines the genetic type of deposit,and establishes the metallogenic model of this Pb-Zn deposit.In the process of mineralization,structure is the main controlling factor,which dominates the formation,migration,migration,precipitation and mineralization of ore-forming fluid by providing power and heat,acting as migration channel and reservoir.The formation mechanism of the deposit is"structural drive-fluid migration along ore-guiding structure→structural deformation-fluid’penetration’along ore-matching structure→fluid mixing and unloading-structure-fluid coupling mineralization".The genetic type of deposit belongs to HZT type,and then build a metallogenic model of"structural control-fluid mixing". |
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