Abstract
Cimabanshuo deposit is a newly discovered porphyry copper (Cu) deposit with giant metallogenic potential, found in the western segment of the Gangdese metallogenic belt, Tibet. The average elevation of the deposit is greater than 5500 m and the terrain on which it is found is steep and complex. Therefore, it is untraversed, and the existing exploration works on it are weak. We used 59 AMT sites belonging to an array covering the main, proven mineralization zone and ore bodies of this deposit for an analysis of its underground electrical structure. Dimensionality and strike analysis revealed the apparent three-dimensional (3D) features near the Cu ore bodies. 3D inversion with topography was conducted for the AMT array data. A large range of high-resistivity anomaly (~500–2000 Ωm) appears beneath the proven Cu mineralization zone and ore bodies, which is interpreted as intrusive rocks with potassic alteration. Although containing chalcopyrite, it is characterized by middle–high resistivity due to a low sulfide content and poor connectivity. Moreover, a series of scattered conductors (~10–300 Ωm) around the Cu ore bodies are distributed in the shallow layer from near the surface to ~200 m, possibly indicating phyllic alteration containing pyritization and connected metal sulfides. The proven ore bodies of Cimabanshuo are mainly located at the junction regions between high-resistivity intrusive rocks and high-conductivity sericitization alteration zones. According to this research, the 3D inversion with topography of AMT data can visually display the 3D distribution of intrusive rocks and alteration zones beneath porphyry Cu deposits in high-elevation regions, and provides a reference for further exploration works.
Highlights
The formation of porphyry copper deposits is generally considered to be related to the hydrothermal fluids released by magma generated within subduction zones [1,2]
We conducted a 3D inversion with topography for 59 audio-frequency magnetotelluric soundings (AMT) sites belonging to an array covering the main mineralization zone and ore bodies of Cimabanshuo Cu porphyry deposit in the western Gangdese metallogenic belt, Tibet
Cu mineralization zone and ore bodies, and is interpreted as intrusive rock with potassic alterations. It is characterized by middle– high resistivity due to low sulfide content and poor connectivity
Summary
The formation of porphyry copper deposits is generally considered to be related to the hydrothermal fluids released by magma generated within subduction zones [1,2]. The alteration and mineral sulfides of the porphyry copper deposit system could show typical zoning characteristics both in vertical and lateral directions centered on the shallow volcanic intrusive complex (Figure 1) [5]. After the above mineralization processes, subsequent regional tectonic movements, such as uplift, result in the gradual denudation of shallow hydrothermal alteration zones and volcanic rocks, causing the outcrop of underlying secondary volcanic. 2 of 15 2 of 15 shallow hydrothermal alteration zones and volcanic rocks, causing the outcrop of underlying secondary volcanic rocks, porphyry mineralization and batholith, which could mroackkes,tphoerapchtyurayl pmoirnpehraylriyzaCtiuonsyasntedmbamthoorleitdhi,vwerhsiechancoduclodmaplsloicmataekde[4th].e actual porphyry Cu syTshteesme pmoorrpehdyirvyeCrsue danepdocsoitms pexlipcaotseedd[t4o].the surface have mostly been discovered and mineTdhineslearpgoerpphoyrpryhyCruy dCeupporsoitvsienxcpesosaerdoutondthtehesuwrfoarcled,hsauvcehmasosthtleyCbaenenaddiiasncoCvoerrdedillaenrad, Amnindeedaninolraorggeenpiocrbpehltyriny CCuhipler,oavnindceGsaanrgoduensdetbheeltwionrTldib, seut c[h4,6a,s7t]h, ebuCtamnaidniearnalCogoirsdtisllsetriall, bAenlideevaenthoraotgtehneiccobneclteainleCdhdileep, oasnidtsGhaanvgedeeqsueablelylt iidneTailboerte[-4f,o6r,m7],inbgutpmotiennetrialos g[i8s]t.sTshtiilsl mbealkieevseitthvaetrythime cpoonrtcaenatletdo idmeapgoesiatsndhaevxepleoqrue athlley uidnedaelrgoroe-ufnodrmstirnugctpuorteenoftitahlses[e8]d. Tahlteerreataiorne tmypaensycEonWta-inanvdeinS-Nlik-ter,emndasinsigvefipnreopfryalcittiuc raensdwwihthitienpphoyrlplichyalrtietriactmionosn. zTohneirteic granite, easrpeemciaanllyyEiWn t-haendroScNks-trtoentdhiengwfeinste ofrfaoctruerbesodwiieths.inTphoerCphuymritiinc emraolnizzoantiiotinc gisracnloitsee, leys-related to tmptmhheoeoecrrdideaeeelfflggryrraraeieccnetetuuotorhfrefeersorsroocoockcccckkfucrsrufartc[roa2tuc[5t2htr]u.i5en]rgw.in.eIgsnt. ooItnfhoeorrtehwbeoorrddwiseo,str.hdTeshm,etiChneuermmaliiinnzaeetrriaaolnliizzwaatoitoiuonlndisbwceloosutsrelodlyngbreeerlaswtterhdoenrtoeger where
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