青海南部茶曲帕查Pb-Zn矿床的勘查历史、现状与下一步找矿方向

从找矿勘查角度,对青海南部新发现的茶曲帕查Pb-Zn矿床的勘查历史和现状进行了介绍,并对下一步找矿方向提出了建议。该矿是2002年以来在1∶20万化探扫面及1∶5万水系沉积物化探发现异常后进一步通过1∶1万地质、化探、激电等综合调查及钻孔工程确定的矿床,目前控制(332+333+334)铅锌资源量99.6万吨。矿区填图表明,北部中新世五道梁组不整合于南部的二叠系九十道班灰岩之上,后者以北倾的逆冲断层和南部那益雄组碎屑岩接触,钻孔资料显示该断层可能为深部由南向北逆冲断层的反冲断层。矿体在孔莫隆矿段主要就位于灰岩内,在茶曲帕查矿段出现在那益雄组和五道梁组中,前者矿体发育好,后者矿化主要见于地表。矿区内圈出4条激电-化探异常,均呈东西向带状分布,分别出现在北部五道梁组、中部九十道班组灰岩、南部那益雄组和五道梁组中。音频大地电磁测深显示灰岩呈相对高阻,碎屑岩、灰岩破碎带、地表水、矿化呈相对低阻。综合分析表明,"三江"北段风火山-囊谦褶皱逆冲带内、与新生代盆地相伴的老于新生代的碳酸盐岩是该类矿床的主要赋矿部位,在矿区范围内,多才玛矿段激电-化探异常带内的灰岩中、地表见矿化、深部具音频大地电磁测深显示的高阻体中相对低阻部位是值得关注的勘查目标。

History, current status, and next targets of exploration in the Chaqupacha Pb-Zn deposit, southern Qinghai Province

As one of the Himalayan sediments-hosted base metal deposits in Sanjiang region,the newly-found Chaqupacha Pb-Zn deposit is less known.This paper deals with its history,current status and next targets of exploration.Mineralization anomalies were found in the ore deposit on the basis of 1∶200 000 and 1∶50 000 geochemical investigations in the period of 2002~2004.Subsequently,the ore bodies were delineated through 1∶10 000 investigations by means of geology,geochemistry and induced polarization(IP) sounding as well as trench excavation and drilling.It has been so far determined that the ore deposit has(332+333+334) Pb+Zn resources of 996 000 tons.Geological mapping shows that marl and mudstone in Miocene Wudaoliang Formation(Nw) unconformably overlies limestone in Permain Jiushidaoban Formaion(Pj) that rides on clastics in Permain Nayixiong Formation(Pn) in terms of a N-dipping thrust fault in the ore zone.This fault was interpreted as a pop up structure of a S-dipping thrust fault found in a drilling hole.Ore bodies in Kongmolong ore block hosted by Pj limestone are apparently better than those in Chaqupacha ore block that is hosted by Nw and Pn strata.Four E-W-striking anomaly belts of IP sounding and geochemistry occur in the Nw-dominated northern segment,the Pj-dominated middle segment,and the Pn-dominated southern segment in the ore deposit,respectively.Audio magnetotelluric(AM) sounding shows that limestone has higher resistivity than clastics,fault zone,water,and ores.It is suggested that Pre-Cenozoic carbonates are prime prospect targets forexploration of this type of ore deposits in Fenghuoshan-Nangqian fold-thrust belt.Within the ore district,the next exploration targets should be relatively lower AM sounding resistivity parts in limestone of Duocaima ore block where mineralization and IP sounding-geochemical anomaly are present on the surface.