【作者】 李冬；

【导师】 张寿庭； 宋要武；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2013， 博士

【摘要】 扬子板块和华北板块在晚三叠纪末完成陆陆碰撞,东秦岭地区进入陆内造山演化阶段,形成区域上北西-近东西向基本构造格架。晚中生代地壳旋转作用,是地表浅部形成北(北)东向构造的原因,构成区域上北西向构造为主,叠加次级北(东)向格子状构造格局。含钼花岗质岩浆沿断裂交汇处侵位,形成区域上众多中酸性斑岩体和钼多金属斑岩和夕卡岩成矿系统。矿集区范围内,构造裂隙产状主体与地层方向一致,沿北(西)西向展布；局部与热液活动密切相关的裂隙沿北(北)东向展布于张性裂隙脉中。157Ma±,构造环境由同碰撞转变为后碰撞,进入汇聚型构造体制下的应力调整阶段；115Ma±,构造环境已转变为板内环境,为拉张型构造体制。146Ma±,板片俯冲作用,是含矿岩体沿构造有利部位(NWW-NE交汇部位)上升的驱动力。栾川矿集区地处东秦岭核心成矿部位。北部中酸性小岩体(以下简称含矿岩体)具有典型“小岩体成大矿”特征,与晚中生代钼多金属大规模成矿作用密切相关；栾川断裂南部老君山,主体岩性为二长花岗岩,呈大的岩基状分布,局部零星钼矿化。两类岩体均为高硅、钾玄岩系列到高钾的钙碱性系列,与Ⅰ型花岗岩类似;均富集轻稀土元素(LREEs),具有Eu负异常。(La/Yb)N、(LalSm)N、Eu值在含矿岩体均要高于老君山岩体,表明含矿岩体经历比老君山岩体更为强烈的分异作用。老君山岩体重稀土(HREEs)元素含量高于含矿岩体,表明在演化过程中,老君山岩体混入更多的地壳物质。同位素综合研究表明,成岩成矿物质主要来源于下地壳,并有地幔成分的混入。含矿岩体多为复式岩体,岩性由早到晚为花岗闪长岩,二长花岗岩,花岗斑岩(部分为细晶岩脉)。与成矿相关二长花岗岩,锆石U-Pb测年结果分别为153.2±1.3Ma,154.1±1.8Ma;细晶岩锆石U-Pb测年结果为148.3±1.0Ma,表明含矿岩浆具有长期演化历史,矿集区内辉钼矿Re-Os测年数据集中在-146Ma。构造地球化学方法表明成矿元素Mo-W-Pb-Zn-Ag具有明显异常峰值,且与指示深部岩浆活动信息的元素组合La-Rb-Sr-K2O同样存在峰值时,指示深部矿化富集程度较高；在矿产勘查详查阶段,CSAMT和SIP的综合应用,对于硫化物矿体定位是有效的方法组合。本文经过综合研究,提出“连续体岩浆房演化模型”来解释栾川矿集区巨量钼的富集作用,正是通过这些花岗质岩浆房的富集作用,形成栾川矿集区巨量的钼多金属堆积。该模型可作为中国东部晚中生代广泛钼成矿作用的典型代表。更多还原

【Abstract】 After the continent to continent collision of the Yangtze and North China Craton in the late Triassic, the basic near EW-NW tectonic lines in east Qinling orogen are formed in the following intracontinental orogeny. Crustal rotations at the late Mesozoic triggered the N(N)E trending faults, and formed a network structure based on the NWW framework and secondary N(N)E fabrics. The Mo bearing granitic magma intruded in the conjunction of the faults, forming the numerous Acid-intermediate porphyritic granites, skarn and porphyry metallogenic system. The statistics of the tectono fissures attitudes, shows that they are mainly occurring in the N(W)W trending, in accordance with that of strata. In some parts, the fissures closely related to the hydrothermal activity are distributed in the N(N)E trending tensional veins. At-157Ma, the tectonic regime was in transition from a syn-collisional to a post-collisional setting, still in the N-S trending convergent tectonic.-115Ma, the tectonic regime changed into within plate, from compression to extension;-146Ma, ore-bearing plutons, which are triggered by slab melts, formed at the junctions of NWW-NE faults.Luanchuan ore belt is located in the key metallogenic area in the east Qinling orogen. Acid-intermediate granites in the north of Luanchuan area (abbr:ore-bearing plutons) are of the characteristics of "small plutons bearing large ore deposits" and are close to the intense Mo-polymetallic mineralization at late Mesozoic; The Laojunshan rock is distributed as batholith in the south, and sparsely Mo mineralization or Mo occurrences are existed. Both the ore-bearing rocks and the Laojunshan rocks are highly siliceous and shoshonitic, high-K calc-alkaline, similar to some I-type granites. Both rock suites are enriched in Light rare earth elements (LREEs) and of negative Eu anomalies.(La/Yb)N ratios, Eu values,(La/Sm)N values in the ore-bearing granitoids have higher concentrations than that of the barren Laojunshan granite suite, confirming the observation that the ore-bearing granites have undergone a higher degree of strong differentiation than that of Lanjunshan batholith. The Laojunshan rocks undergone greater fractionation of heavy rare earth elements (HREEs), indicating more crustal materials were contaminated in the granitic evolution process. Comprehensive isotopic study suggests that the metallogenic and lithogenetic materials are mainly from lower crust, involvement with parts of mantle composition.Ore-bearing rocks are complex plutons, including granodiorite, monzonitic granite and porphyries (or aplites) from early to late. The isotopic ages of monzonitic granites from deep boreholes are153.2±1.3Ma,154.1±1.8Ma, respectively. Zircon isotopic age of aplite from ore adit is148.3±1.0Ma, suggesting that the evolution of Mo-bearing granitic magma is long, Re-Os data are concentrated in-146Ma.The place where tectono-geochemistry method shows that ore-forming elements, such as Mo-W-Pb-Zn-Ag are of evident anomalies which are coincide with the La-Rb-Sr-K2O anomalies have the higher potential of mineralization in the deep; in the stage of detailed mineral exploration, comprehensive application of CSAMT and SIP is a effective method for ore body positioning.A new model called continuum model that ore-bearing granites experienced sequential chamber evolutions is proposed to explain the Mo enrichment processes. It is through the sequential granitic chambers that Mo was gradually enriched. Finally, huge Mo reserves were accumulated in the Luanchuan ore belt. The model might be a paradigm in explaining the pervasive Mo genesis in late Mesozoic of the east China.更多还原