Research On Metalliferous Deposit Mineralization And Survey And Prediction Of Target Area For Mineral Prospecting Mian-lue-Ning Region, Shaanxi

Located in northwestern margin of the Yangtze Platform and eastern end of the MotianlingTectonic Belt,Mian-Lue-Ning Region(MLNR)is a composite landmass coalesced by the LateArchaean Yudongzi Block and Meso-Neoproterozoic Bikou Block through the Jinning TectonicEvent.These two blocks were respectively accreted to the northern margin of the Yangtze Plateand the Qinling Microplate after the Caledonian Tectonic Event,together constituting animportant part of the Qinling Orogenic Belt.The north-west spreding Mian-Lue TectonicMelange Belt and the north-east spreading Hanjiang Fault,respectively to the north and southof the research target region,tectonically outline the boundaries between the research targetregion and the Qinling Orogenic Belt as well as the Yangtze Plate.The triangle-shape researchregion is gifted with most significant endogenetic mineral resources in southern Qinling andgeographically named"Mian-Lue-Ning Triangle(Region)".Considering the complex tectonic and metallogenetic background in the region,thisresearch systematically focused on the lithologic-tectonic setting of basal igneous rocks,fundamental geology of the Magmatic-Tectonic Belt resulted from the basal coalescence and theMian-Lue Tectonic Melange Belt,and their related primary metallogeneses.Thiscomprehensive research involved a variety of metallogeneses relevant to lithologic-tectonicsetting,ore-bearing fluids,tectonic shear-thrust system,etc.In addition,based on theanalysis of rudimental metallogeneses,the author thoroughly classified the metallogeneticseries and dissected some typical mineral deposits in this region.Based on detailed research onmetallogenetic rules and mineral-prospecting signitures,the author carried out large-scaleprospecting work on the prediction of mineral resources in this region.This work has offeredfavorable orientations for and will contribute to prospective mineral surveys in Mian-Lue-NingRegion.The primary theoretic and practical achievements for mineral prospecting are summedup as follows:1.Based on analysis of basic geological backgrounds and various tectonic architectures inthis region,this paper discusses the developmental processes and interior structures of the basalMagmatic-Tectonic Belt and the Mian-Lue Tectonic Belt,the author proposes the essential tectonic framework of Mian-Lue-Ning Region as"Two Blocks and Three Belts",whichprovided tectonically significant advantages for diageneses and mineralogeneses.TheXujiaba-Heimulin-Xiakouyi-Jianchaling ultramafic-mafic or intermediate-acidic magmatic rocksas well as linear volcanic systems serve as indicative signatures of the basement coalescence,which was previously split north-southward and subsequently folded and deformed by regionalcompressions.Thus the author presents that the formerly-formed ultramafic intrusives in thecoalescence belt have bedded or sub-bedded structure and experienced later folding synchronousto the overlying stratigraphic succession,concluding that the central Basement CoalescenceBelt and the Mian-Lue Tectonic Melange Belt,though representing different special andtemporal evolution pathways yet sharing analogous interior structures and diagenetic andmetallogenetic characteristics,both yield paramount bonanzas in this region.2.The author systematically and innovatively discusses and classifies the metallogeneticseries and corresponding control factors.Metallogenetically concentrated localities with similargeological and mineralogenetic advantages are utilized as templates to probe into the JianchalingAu-Ni deposit,Tongchang Cu deposit,Dongouba Au-polymetallic deposit and Ganheba Audeposit.After comparison and investigation,the author revealed the close relationship betweenthe primary metallogeneses and the presence of ultramafic rocks,intermediate-acidic(or acidic)rocks and mafic volcanic-sedimentary rocks,consequently reasoning out an effective model formineral prospecting in the Mian-Lue-Ning Region.Considering geological information acquiredfrom the Jianchaling Au deposit during mining in the depth as well as from recent progress ofmineral prospecting in the southern belt,this paper,for the first time,presents that auriferousenrichments tend to occur where the primary shearing fault(F⁴⁵)gave rise to subordinate faultsthat intersected the primary fault plane during late thrust and shear resulting in the accumulationand expansion of orebodies,instead of occurring where the dip of the primary fault planechanged.Accordingly,the author recommends to pay more attention to deep-seated intersectingsub-faults together with ultramafic wallrocks in terms of prospecting for enriched mineralresources.3.Based on petrologic-tectonic mineralogenetic theories,this research explicates theYudongzi Block,Bikou Block,Basement Coalescence Belt as well as the petrologic-tectonicsetting and corresponding metallogeneses in this region,indicates that the volcanogeneticGuojiagou Formation and Donggouba Formation of Bikou Group are litho-tectonicallycharacterized by alkali-series oceanic tholeiite and island-arc tholeiite respectively,indicativeof oceanic rifting & depressing and island-arc palaeogeography.The litho-tectonic analysis on ultramafic,intermediate-acidic and acidic intrusive rocks show they originated from ahomologous chamber yet from different intrusive stages.4.Based on modern metallogenetic theories on plutonic fluids and shear belts,themetallogeneses in this region can be classified into four categories,i.e.,(1)source-elementmetallogenesis,(2)magmatic-tectonic metallogenesis,(3)fluid metallogenesis,and(4)shear-thrust metallogenesis.Systematical studies were also implemented regarding thetheoretical foundation of various metallogeneses and concrete geological phenomena,especially the influences of crust-and mental-originated fluids on the alteration ormetallogeneses of the Jianchaling Ni enrichment,Jianchaling Au alteration deposit anddKuangchang Cu hydrothermal deposit.The author herein highlights that all the metallogeneseswere rudimentally based on the multistage evolution of the Basement Coalescence Belt and theMian-Lue tectonic Belt.These various metallogeneses provided necessary pathways for theconcentration,transportation and preservation of mineral resources in this region.5.After integrating the regional mineralogenetic rules,this research exhaustively depictsthe relationship between significant geological events and metallogeneses,and indicates thespecial and temporal connections between tectonic evolutions and metallogenetic progresses.6.To provide detailed,precise and practical guidance for mineral prospecting inMian-Lue-Ning Region,the author,after fully taking into account previous problems inmineral resources predictions,refines his experience and achievements obtained in the pastdecades of years into establishing some principles for prospecting and prediction of targetresources in the region,i.e.,indicating three prospective resource key targets including theXujiagou,Jinzishan,Jianchaling(southern belt)and four candidates.As a matter of fact,these prospective targets have well stood the test and verification of the subsequent mining andshow desirable effects in prediction.Thus the theory,method and guidance of this researchproved practical and feasible.As a result,the other prospective resource targets will beconsequently favorably verified.Conclusively,the prospecting signatures established in thisresearch are providing indicative guidance and effective methods for geological surveys inMian-Lue-Ning Region.