Metallogenesis Of Gold Deposits In Gouli Regional And Peripheral Area Of East Kunlun, Qinghai Province

Gouli area is located in the eastern section of East Kunlun orogenic belt (EKOB). Inrecent years, many gold deposits have been found. This paper uses metallogenic theory,combined with mineralization dynamical evolution of EKOB, to analysis tectonic setting,geological characteristics, ore-forming fluid and mineral sources of typical deposits, todiscuss the genesis, to establish metallogenic series and a metallogenic mode, to carry outpotential evaluation of gold mineralization (prospecting).The paper proposes the existence of upper mantle gold in the middle and south beltsof East Kunlun area. During the repeatedly basaltic magmatism process of PrecambrianEast Kunlun, a small percentage melting of lithospheric mantle produced silicate meltforming sulfur supersaturation, and sulphide melt and silicate melt segregated in theregion. Because the sulphide density is much larger than silicate density, sulfides areresorted in the upper mantle. Meanwhile, due to distribution coefficient of gold and othermetals in the sulfide are four orders of magnitude than that in the silicate melt, gold andother metals together with sulphides are stranded on the lithospheric upper mantle,forming upper mantle gold of East Kunlun. Gold in sulfide of upper mantle is moreactivated than that in silicate, easy to be carried to the crust by mantle CHO fluid,involved in mineralization.To analyze the typical deposit, discuss the genesis. Sulfur, lead, hydrogen and oxygen isotope studies indicate that ore-forming fluids with characteristics of mantle, mineralmainly derived from the upper mantle. Lamprophyre and gold belong to the differentiationevolution product of mantle CHO fluid at different stages. High gold content oflamprophyre is important evidence of mantle fluids carrying gold derived from uppermantle. It is supposed that mantle gold involved in the mineralization in East Kunlunregion.Through comprehensive analysis and demonstration, Dalijigetang gold deposit isporphyry type. Wall-rock alterations are developed, with the characteristics of a large areasurface alteration and mineralization, and have zonation. Alterations are mainly phyllic(like phyllite), argillization and propylitization; ore structure characteristic manifestsveinlet, brecciated structure, etc.; fluid inclusion study displays low salinity and lowdensity of ore-forming fluids; composition of fluid inclusions generally containing CO2,CH4through laser Raman spectroscopy, that means ore-forming fluid isCH4-CO2-H2O-NaCl system, showing the characteristics of mantle fluid; formationtemperature of quartz sericite zone is from147.6℃to435.7℃, the peak is between260℃and320℃. It is the first time that it determines the porphyry gold deposits in thewhole East Kunlun area.Through comprehensive analysis, Kengdenongshe gold polymetallic deposits are ofepithermal deposits, not previously considered sedimentation-exhalation origin. The mainwall-rock alterations is barite, silicification, carbonation, dolomitization, chlorite, etc.,showing mainly low-temperature alteration mineral assemblages, barite not previouslyconsidered sedimentation-exhalation causes; fluid inclusion homogenization temperaturesis of101~190℃, mainly in the peak of120~160℃. The deposit is controlled byextensional tectonic regime.Establish gold metallogenic series of Gouli regional and peripheral area:" Indosiniangold mineralization series of Gouli area, East Kunlun ", and it is divided into threesub-series, porphyry-type, orogenic-type and epithermal-type metallogenic sub-series,three deposit styles, namely, Dalijigetang style, Guoluolongwa style and kengdenongshestyle. Establish metallogenic models of three deposit types of Gouli regional and peripheralarea:1. Orogenic gold metallogenic model:(1) Orogenic mantle CHO fluid metallogenicmodel: Late Indosinian, extension caused lithospheric delamination and thinning, mantleCHO fluid influxing into upper mantle gold, extraction of gold and other mineralstransporting to precipitate in a suitable structure site, forming orogenic gold deposits ofthe region;(2) Orogenic gold continuous metallogenic model at different depths in thecrust: It has the characteristics of continuous mineralization at different depths, frommeso-hypozonal (Asiha gold deposit) to meso-epizonal (Annage gold deposit) to epizonal(Guoluolongwa gold deposit), mineralization depth being8.16~9.58km,6.88~8.86kmand4.77~7.65km respectively, mineralization depth turning shallow, ore-forming fluidtemperature transition ranging from155℃to425℃.2. Porphyry gold metallogenic model: the formation of deposits in the transformationtectonic setting of Indosinian from extrusion to extension system, mantle-derivedsubstances involved in mineralization.3. Epithermal gold-polymetallic metallogenic model: the tectonic setting of thedeposit formed in post-orogenic stretch background of late Indosinian (?), mantle-derivedsubstances involved in mineralization.Summarizes the mineralization enrichment regularity, and analyzes the depositerosion and preservation conditions, to carry out gold mineralization (prospecting)potential evaluation. It is suggested that Guoluolongwa gold deposit and kengdenongshegold polymetallic deposits has great prospecting potential. And based on the lateralcorresponding theoretical, it predicts that another fault of the two main faults ofKengdenongshe deposits has prospecting potential, which should be the focus of next stepexploration work.