【作者】 李冰；

【导师】 赵志丹；

【作者基本信息】 中国地质大学（北京） ， 地球化学， 2006， 硕士

【摘要】 驱龙斑岩铜（钼）矿床位于西藏墨竹工卡县境内,大地构造位置上处于冈底斯东段陆缘岩浆弧中的“拉萨—日多弧内局限盆地”的南部边缘。矿区出露中朱罗统叶巴组火山次火山沉积岩、古新世黑云母花岗斑岩、中新世二长石英斑岩以及渐新世花岗斑岩。目前该矿床已圈定含矿斑岩体4个,铜矿体5个,矿化深度大于500m,是冈底斯喜山期斑岩型铜钼矿带东段发现的最具找矿潜力的斑岩铜（钼）矿床,也是该带斑岩矿床勘查的重大突破。 本次研究工作主要针对驱龙斑岩铜（钼）矿床含矿斑岩体,分别从矿物化学特征,主量元素、微量元素、稀土元素以及同位素地球化学特征等几个方面进行详细研究,并通过与冈底斯成矿带其它典型矿床的对比分析,进而研究总结该成矿带斑岩矿床的时空分布特征、矿化蚀变特征、成矿构造背景,并初步探讨其物质来源和成矿机理等。 驱龙矿区矿化斑岩有二长石英斑岩和黑云母花岗斑岩,呈岩株状产出,浅成侵位于中朱罗统叶巴组火山岩内。黑云母花岗斑岩侵入凝灰岩与流纹斑岩中,而二长石英斑岩侵位于黑云母花岗斑岩和流纹斑岩中。铜（钼）矿（化）体主要产于含矿斑岩体和黑云母花岗斑岩的内外接触带中。 对驱龙含矿斑岩铜钼矿体中辉钼矿进行Re-Os模式年龄测定,其成矿年龄为15.82±0.19～16.85±0.19Ma。驱龙斑岩铜矿黑云母花岗斑岩SHRIMP锆石U-Pb年龄为15.9±0.7Ma,与Re-Os年龄非常一致,与文献报道的成矿母岩二长石英斑岩侵入年龄为14-20Ma接近,表明驱龙矿床成矿时间与斑岩体的形成基本同时。 驱龙矿床岩石具有高SiO₂、富K₂O及Na₂O、低CaO和TiO₂的特点:铝饱和指数A/CNK<1;绝大多数岩石的里特曼指数<3.3。含矿斑岩应属于偏铝质高钾钙碱性岩石。岩石明显富集大离子亲石元素:K、Rb、Sr、U;而亏损高场强元素Nb、Ta、Ti和Y;富集轻稀土元素,Eu负异常不明显。驱龙及冈底斯带其它典型斑岩矿床含矿斑岩都具有Ⅱ类埃达克岩特征,但又有其特殊性。 驱龙铜矿含矿斑岩常见的蚀变为钾长石化、黑云母化、硅化、绢云母化和局部的粘土化等。斑岩体由内到外,大致可划分为钾硅酸岩化带、石英-绢云母化带、青磐岩化带,泥化蚀变不发育。其中钾硅酸盐化蚀变期是最重要的成矿时期,稍晚的石英绢云母化蚀变期次之。 与世界上大多数斑岩型矿床产在挤压弧系（主要为陆缘弧和岛弧）不同,驱龙及其它冈底斯带斑岩铜矿床的成岩成矿作用发生在西藏陆陆碰撞造山后期的地壳伸展阶段。由此产生的一系列近南北向张性构造,成为冈底斯带含矿斑岩的就位场所。 通过以上的岩石学特征、微量元素组成以及Pb—Sr—Nd同位素示踪分析,冈底斯带斑岩铜矿床的岩浆起源可能与特提斯俯冲洋壳、玄武质增厚下地壳以及大洋沉积物有关,并经历了与亏损地幔、富集地幔（EMⅡ）的混合以及下地壳部分熔融、上地壳物质混染等多种地质作用,显示其岩浆来源的复杂性。更多还原

【Abstract】 Qulong porphyry copper （molybdenum） deposit is located in Mozugongka County, Tibet. It situated in the southern margin of Lhasa-Riduo localization basin of the continental margin magmatic arc in east Gangdese belt. The middle Jurassic Yeba formation volcanics, Paleocene biotite granite porphyry, Miocene quartz monzonite and Oligocene granite porphyry could be found in the ore field. Four mineralized porphyry bodies and five copper ore bodys, which locate in the depth over 500 m, have been distinguished in Qulong. It is one of the biggest breakthrough of ore prospecting in Tibet. Qulong also have the potentiality of being a super large porphyry copper （molybdenum） deposit in the eastern Gangdese porphyry copper belt.This research mainly aims at the ore-bearing porphyry bodies, by studying the mineral chemistry, major and the trace element geochemistry, and isotope geochemistry. By comparing to other typical deposits in this metallogenic belt, the characters of spatiotemporal distribution, mineralization, alteration and structural setting, and petrogenesis are also summarized.The ore-bearing biotite granite porphyry and quartz monzonite emplaced in the Jurassic Yeba formation volcanics. The biotite granite porphyry emplaced in the tuff and rhyolite porphyry, and the quartz monzonitic emplaced in the biotite granite porphyry and the rhyolite porphyry. The copper （molybdenum） ore bodies are mainly situated in or out of the contact zone between the mineralized porphyry bodies and the biotite granite porphyry.The Re-Os model ages yielded by molybdenite from the Qulong porphyry deposit range from 15.82±0.19 to 16.85 ± 0.19 Ma. The SHRIMP zircon U-Pb measurement of the biotite granite porphyry yielded the age of 15.9±0.7 Ma.This is very consistent with the published data （14-20Ma） of the quartz monzonite in the whole Gangdese belt.The porphyries characterized by high - SiO₂, K₂O and N₂O and low CaO and TiO₂. The aluminium saturation indexes （A/CNK） are less than 1, the Rittmann Indexes are mostly less than 3.3. So they belong to dominative aluminous high-K cale-alkaline series rocks. The rocks are enriched in LILE （e.g. K, Rb, Sr, U） and LREE, and depleted in HFSE （e.g., Nb, Ta, Ti, Y） and HREE. The Eu negative anomaly is inconspicuous. The porphyries show adakite magmatic affinity withparticularity, which suggest the complexity of the magma origin.The common alterations are potash feldsparize, biotitize, silicification, sericitization and partial argillation with the mineralized porphyries. The alteration zoning is analogous to the model of Lowell and Guilbert, with typical "face type" feature. The concentric alteration zones from the inner outward are successively the K-silicate zone, the quartz-sericite zone, and the propylitic zone, but the argillatio zone is on rare occasion. The orebodies mostly occur in the K-silicate alteration periods, and the later quartz-sericite periods take second place.Different from the most porphyry deposits which generate in extruding environment （mainly continental margin arc and island arc）, the diagenesis and mineralization of the Gangdese porphyry copper belt took place during post-CoUis ional crustal extension period. The mineralized porphyry bodies were locally controlled by the near NS-striking extension tectonics.The characteristics of the geognosy, the rare elements compositions and the signatures of Sr, Nd and Pb isotope of the rocks inferred that the mineralized porphyry related to the tethys subducted oceanic crust, the basaltic lower crust and the oceanic deposit, coupled with the exchange of substance with the depletion mantle and the enrichment mantle II （EM II） as well as the lower crust partial melting and the up-crust contamination. All of that show the complexity of magmatic origin.更多还原