摘要
在南祁连构造带西段柴达木山地区新发现的额里肯达云英岩型锡矿床表明,该区具备寻找大规模锡矿床的可能。然而,该地区与锡矿化密切相关的花岗岩的时代与成因、成矿地质环境和找矿前景并不清楚。本文报道了柴达木山新发现的额里肯达锡矿床相关的花岗岩的地质、地球化学特征和形成时代。额里肯达花岗岩不含暗色铁镁质微粒包体和捕虏体,暗色矿物为黑云母(<5vol%),含极少量白云母和电气石。LA-ICP-MS锆石、独居石和锡石U-Pb定年确定花岗岩成岩时代为436~434Ma,锡矿床成矿年龄为435~432Ma,均为早志留世。额里肯达花岗岩主量元素组成具有高SiO_(2)和Na_(2)O+K_(2)O,低CaO、MgO和Fe_(2)O^(T)_(3)等特征,属于弱过铝质。其微量元素组成具有典型的“海鸥型”球粒陨石标准化配分模式图,并具高Rb/Sr(11.4~133)和Rb/Ba(1.77~115)比值以及低Zr/Hf(19~30)和Nb/Ta(4.8~9.2)比值。其锆石ε_(Hf)(t)值介于-10.49~-5.18,二阶段模式年龄为2.08~1.74Ga,全岩ε_(Nd)(t)值为-9.15~-8.34,Nd模式年龄(t_(DM2))为1.93~1.86Ga。额里肯达花岗岩展示了高分异花岗岩的特征,其岩浆母源主要来自形成于同碰撞构造环境下的古元古代地壳,热源可能与俯冲板片断离或回撤导致的幔源岩浆底侵相关。额里肯达花岗侵入体是该地区云英岩型锡矿床成矿物质的来源,而与额里肯达花岗岩锆石Hf同位素组成相似的、具高分异特征的早志留世花岗岩在柴达木山分布广泛。近期柴达木山地区矿产调查评价和勘查工作在该地区发现了大量与这些早志留世花岗岩伴生的锡矿床或矿点,这表明该区锡成矿潜力巨大,“柴达木山锡矿矿集区”的雏形已经显现。
The newly discovered Erlikenda greisen-type tin deposit indicates that the Qaidam Mountain in the western segment of the South Qilian tectonic belt has a possible potential for forming large-scale tin deposits.However,the formation time and petrogenesis of granites associated with the newly discovered tin deposit in the Qaidam Mountain,and related metallogenic geological setting and prospecting potential in this area remain unclear.This study reports geological and geochemical characteristics and formation time of the Erlikenda granites.The Erlikenda granites contain no dark ferromagnesian micro-inclusions and xenoliths.They contain biotites(less than 5vol%)with a very small amount of muscovite and tourmaline.LA-ICP-MS zircon,monazite and cassiterite U-Pb isotopic dating indicates that the Erlikenda granites and tin mineralization occurred in 435~434Ma,and 435~432Ma,respectively,indicating that the magmatism and tin mineralization are coeval(the Early Silurian).The Erlikenda granites have high contents of SiO_(2)and Na_(2)O+K 2O,low contents of CaO,MgO,and total Fe_(2)O_(3),and are weakly peraluminous.They have a typical“seagull-type”chondrite-normalized distribution patterns,with high Rb/Sr(11.4~133)and Rb/Ba(1.77~115)and low Zr/Hf(19~30)and Nb/Ta(4.8~9.2)ratios.The zirconε_(Hf)(t)values of these granites range from-10.49 to-5.18 with two-stage model ages of 2.08~1.74Ga.Furthermore,these rocks have whole-rockε_(Nd)(t)values ranging from-9.15 to-8.34 with the Nd isotopic model ages(t_(DM2))of 1.93~1.86Ga.The Erlikenda granites have highly fractionated granite characteristics,which mainly originated from the Paleoproterozoic crust.They may be formed in a syn-collisional tectonic environment,which was possibly related to the underplating of mantle-derived magmas as a result of the breakoff or rollback of the subducted plate.The Erlikenda granitic magmatism possibly caused the greisen-type tin mineralization in this area.These highly fractionated Early Silurian granites with zircon Hf isotopic compositions similar to those of the Erlikenda granites which widely occur in the Qaidam Mountain.In the recent mineral investigation,evaluation and exploration work,a large number of tin deposits or mineralized spots associated with Early Silurian granites have been discovered in the Qaidam Mountain,indicating that this area has an important potential for forming large-scale tin deposits,i.e.,the Qaidam Mountain tin ore concentration area will be developed soon.
作者
王秉璋
王强
王涛
焦和
李五福
权朝军
王春涛
赵子送
WANG BingZhang;WANG Qiang;WANG Tao;JIAO He;LI WuFu;QUAN ChaoJun;WANG ChunTao;ZHAO ZiSong(Bureau of Geological Exploration&Development of Qinghai Province,Xining 810001,China;Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Xining 810012,China;State Key Laboratory of Deep Earth Processes and Resources,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Qaidam Comprehensive Geological and Mineral Exploration Institute of Qinghai Province,Golmud 816099,China;Geological Survey Institute of Qinghai Province,Xining 810012,China)
出处
《岩石学报》
北大核心
2026年第1期71-98,共28页
Acta Petrologica Sinica
基金
自然科学基金项目(42430311、92062217)
青海省地质矿产勘查开发局项目(青地矿[2021]61号)联合资助.
关键词
勘查意义
成矿背景
岩石成因
锡矿
柴达木山
南祁连带
Exploration implications
Metallogenic setting
Petrogenesis
Tin deposit
Qaidam Mountain
South Qilian Orogenic Belt
