东秦岭西坝花岗岩体及其脉岩的地球化学特征

通过秦岭西坝花岗岩体及邻区脉岩体的岩石学、地球化学研究，探讨了秦岭造山带中生代期间由全面碰撞转入陆内造山的深部动力学过程。研究表明：西坝花岗岩体及花岗斑岩脉具类似于埃达克质岩高Sr(Ba)，低Y和Yb，以及高Sr/Y,La/Yb,Eu异常微弱的地球化学特征，反映其形成于地壳厚度增大的地质背景；闪长玢岩脉代表地壳减薄背景的产物。它们的形成指示秦岭造山带印支晚期到燕山早期地壳增厚，嗣后发生下地壳拆沉的重要转换过程。     

东秦岭造山带南部宁陕花岗岩体群的地球化学及其构造环境研究

本文详细研究了东秦岭造山带南部宁陕花岗岩体群的地质特征、岩石学、矿物学和地球化学特征.宁陕岩体群为钙碱性-碱性系列的花岗岩基,主要副矿物为钛铁矿、磷灰石、锆石和独居石,其黑云母为铁质黑云母,SiO_2和碱质含量都较高,除V,Sc,Sr和Bi等元素之外的大多数元素出现亏损;稀土元素负Eu异常较为明显,其组成模式为右倾“V”形曲线;δ~(18)O较高,而初始锶比值相对较低.因此,宁陕岩体群花岗岩为S型花岗岩.作者用多元统计分析和图解法将本岩体群花岗岩与世界著名造山带花岗岩的地球化学特征进行了对比研究,认为本岩体群花岗岩为陆-陆碰撞型花岗岩,是扬子板块与华北板块在晚古生代期间发生对接碰撞的产物.     

青海南山早三叠世石英闪长岩地球化学特征、LA-ICP-MS定年及地质意义

为了研究青海南山早三叠世石英闪长岩的成岩时代、构造环境、地球化学等特征,通过对岩体中主量元素、稀土元素、微量元素及LA-ICP-MS同位素定年等方面的样品数据统计分析,结果表明:岩体的成岩时代为早三叠世;主量元素总体呈偏铝质的高钾钙碱性岩石,具I型花岗岩的特点;岩体在成岩过程中经历了较强的结晶分异和地壳重熔作用,是印支期拉脊山造山带向南俯冲与西秦岭造山带碰撞后的构造产物。为了解早三叠世青海南山所处的大地构造环境提供理论依据。     

造山运动与秦岭造山

对造山运动概念的演变进行了讨论，提出了分析秦岭造山作用的现实原则基础。根据秦岭造山带区域地质构造演化和不同时期、不同类型造山作用的研究，划分出俯冲、碰撞和陆内造山作用3个主要阶段。其中碰撞造山作用可进一步分为弧—陆碰撞和陆—陆碰撞阶段。研究认为：秦岭地区古生代以来随着板块构造体制向陆内构造体制的复杂转化，经历了多次、多种类型造山作用的复合叠加，仅仅根据经典板块造山模式不能对秦岭演化历史作出完整解释；受古特提斯东部构造城独特的构造背景控制，即使在古生代—早中生代板块构造体制阶段，秦岭造山作用的细节过程也表现出与传统板块作用明显不同的特征。     

甘肃北山明水岩基地质特征及成因讨论

明水岩基是甘肃北山北带规模较大的复式岩基之一,野外调查表明,由新井岩体(早期)、明水岩体(中期)和大石山岩体(晚期)组成。其中,新井岩体侵位时代为早石炭世(314Ma),明水岩体形成于晚石炭世,而大石山岩体为中二叠世(273Ma)。通过对岩基岩石学、岩石地球化学的研究,初步认为新井岩体属埃达克岩,具高硅(Si O256%),富铝(Al2O3≥16%)、低镁(Mg O3%)的特征,微量元素中富集大离子亲石元素Sr,亏损Yb和Y等重稀土元素及高场强元素(Nb、Hf和Ti等);明水岩体岩石中见白云母、石榴石等富铝矿物,A/NCK1.1,属S型花岗岩;而大石山岩体则为A型花岗岩。结合区域地质演化,认为新井岩体可能为晚石炭世早期,红石山洋向南俯冲过程中,俯冲洋壳板片部分熔融形成,明水岩体为板块俯冲结束后陆陆碰撞的结果,而大石山岩体为碰撞后陆内伸展的产物。     

东秦岭丹凤地区钾长花岗岩年龄、地球化学特征及其地质意义

东秦岭丹凤地区古生代构造岩浆活动十分活跃。为进一步约束早古生代后碰撞阶段的开始时间,通过LA-ICP-MS锆石U-Pb年龄、主量元素和微量元素测定,对马莲滩一带产出的钾长花岗岩进行了岩相学、地球化学和同位素年代学研究。结果表明,砖红色钾长花岗岩是高硅(71.79%～72.99%)、过钾质(K_2O/Na_2O 3.02～4.32)、偏碱(AI值0.80～0.89)的过铝质(A/CNK值1.03～1.16)S型花岗岩,它相对富集大离子亲石元素Rb、Th、U、Pb,明显亏损Ba、Nb、Ta、Sr、Ti等元素,其轻稀土元素分馏较强、重稀土元素分馏较弱且铕负异常。其岩浆锆石在CL图像上颜色较深,协和年龄为(430.8±2.6) Ma。该钾长花岗岩是后碰撞构造环境下由富含黏土质或泥质岩石低度部分熔融形成的岩浆岩,它约束了东秦岭地区古生代碰撞造山的结束时间,标志着早古生代碰撞造山作用进入后碰撞阶段(第二期第四阶段)。     

东秦岭造山带形成过程新探索

根据秦岭造山带郯庐断裂以东部分（本文称东秦岭造山带）的地质和地球物理特征，对东秦岭造山带的形成过程作了新的探索；并有新的造山作用模式解释了下扬子地区的性质，郯庐断裂为何中于大别山南缘突然中止以及秦岭造山带为何被一分为二等重要问题。     

蟒西地区中酸性岩体地质特征及找矿潜力

通过对陕西蟒西地区中酸性岩体地质、地层、岩体构造等进行论述,归纳总结了区域中酸性岩体的特征,并通过矿床分析得出,陕西秦岭东部地区钼矿床地质学基本特征与中国内陆地区的大部分钼矿床的地质特征大致相同,其中Eu含量有所异常,K、Ra、Ba、Nb、Ta等元素的含量较为丰富,Ti为亏损状态;造山环境下易形成矿与岩;秦岭北部地区含矿岩浆中含有更多的壳液物质,南秦岭北部钼矿床含矿岩浆中含有较多的幔源物质。秦岭南部的大型岩体中原位Hf同位素特征值较高(-6.0～5.0,通常为负数),但是亏损地幔二阶段年龄的值较低(1.47～0.79 Ga),相关数据结果表明岩浆的来源为幔源物质与新生的加厚地壳。可见,地质和地球化学特征指示,秦岭地区有形成钼矿床的有利条件,形成小-中型铜、钼矿床的潜力大。     

秦岭造山带佛坪地区花岗岩类的特征及其意义

通过岩石学和地球化学研究，认为佛坪地区花岗岩类可分为两种不同的成因类型：深熔混合岩化型和陆壳重熔型。它们具有截然不同的野外地质特征和稀土元素地球化学特征，反映造山带不同演化阶段的构造热事件。深熔混合岩化小岩体与晋宁期南秦岭强烈变质变形密切相关；大面积出露的陆壳重熔型岩体则是主造山期地慢上涌引起的垂向加积构造演化的物质反映，对佛坪穹窿的形成和穹窿中心基底结晶杂岩的抬升剥露有重要意义．     

大柴旦塔塔棱河北部地区二长花岗岩岩体地球化学特征

为了研究大柴旦塔塔棱河北部地区早志留世侵入岩的地球化学特征,本文通过全岩地球化学分析方法对塔塔棱河北部地区二长花岗岩岩体进行研究,结果表明:Na_2OK_2O,K_2O/Na_2O为1.97～3.06,为富钾型;里特曼指数σ为2.01～2.52,其值小于3.3,为钙碱性岩石;铝饱和指数A/CNK为1.07～1.26,属过铝质岩石,总体显示过铝质、高钾钙碱质花岗岩类。LREE/HREE为8.78～12.06,δCe值为0.90～0.99,δEu值为0.36～0.50,Eu具有明显负异常;总体显示轻稀土元素富集。微量元素显示Rb,Th,La,Ce,Nd,Hf元素富集;U,Nb,Lu,Sr,P元素亏损。通过构造环境判别分析得知该研究区早志留世二长花岗岩总体具后造山花岗岩特征,形成于属后碰撞造山构造环境。     

秦岭柞水岩体和东江口岩体的锆石U-Pb 年代学及其意义

柞水岩体和东江口岩体位于秦岭造山带南秦岭构造域, 主要由似斑状花岗闪长岩和二长花岗岩组成。通过LA-ICP-MS 锆石U-Pb 同位素定年, 结合锆石阴极发光图像, 揭示柞水岩体的似斑状二长花岗岩(样品ZS01-01)存在两个谐和年龄, 分别为209±2和199±2Ma;东江口岩体似斑状二长花岗岩(样品ZS04-01)也存在两个谐和年龄, 分别为219±2 和209±2 Ma。结合前人的地球化学和区域构造背景研究, 判定这两个岩体属于同一岩浆事件的不同阶段侵位, 东江口岩体的似斑状二长花岗岩侵位结晶略早于柞水岩体, 柞水岩体主期岩浆侵位时, 东江口岩体也有同期岩浆侵位结晶。这两个岩体年龄的准确测定, 表明在219 ～199 Ma 期间沿商丹断裂有3个阶段的构造-岩浆活动。     

Rb-Sr chronological characteristics of Jurassic granitoid gravels in north margin of Dabie block, Central China

Granitoid gravels are discovered from alluvial fan conglomerates, the base of Jurassic Fenghuangtai Formation (J₂ ²), in the north margin of Dabie block and the south part of the Hefei Basin. These granitoid gravels make up 5%–10% of all gravels by volume percent. For the four components, K-feldspar, biotite, amphibole and whole rock divided from two selected granitoid gravel samples, their Rb-Sr isotopes are measured, which gives two formation ages of granitoids: (428±20) Ma and (430±54) Ma, and means that the Early Paleozoic granitoid intrusive rocks once existed in the Dabie Mountain provenances of Jurassic. The granitoids occur in the tectonic setting of post-collision uplift according to lithogeochemical discriminant analysis.     

Zircon U-Pb age of the Shacun gabbro body, Yuexi, Dabie orogen and its geological implications

The single grain zircon U-Pb age of the Shacun mafic-ultramafic intrusion, Yuexi, North Dabie is (128.1±2.0) Ma. This date indicates that the intrusion was implaced at Yanshanian when most Mesozoic granitoids were intruded. It was not the syn-collisional intrusion related to the subduction of the Yangtze Block and ultrahigh-pressure metamorphism at Indosinian.     

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma, respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the Changba intrusion, yielding a weighted mean of ²⁰⁶Pb/²³⁸U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO₂ and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process may be coupled with exhumation of the subducted continental crust in the stage of late collision.     

Discovery of the Early Paleozoic post-collisional granites in northern margin of the Erguna massif and its geological significance

The Luoguhe intrusion, located in Mohe County, Heilongjiang Province, is mainly composed of monzogranite, quartz diorite and granodiorite, with minor diorite, tonalite, quartz monzodiorite, quartz monzonite, syenogranite and alkali-feldspar granite. The intrusion can be divided into two iithological units, i.e. quartz diorite and monzogranite units, with affinities to high-K caic-alkaline series. The quartz diorite unit （SiO2： 54.79%-58.30%, Na2O/CaO： 0.79-1.53 and Shand index： 0.77-0.82） belongs to metaluminous rocks. And the monzogranite unit （SiO2： 65.29%-66.45%, Na2O/CaO： 1.73-3.43 and Shand index 〈1.05） can be considered as weakly peraluminous rocks. The intrusion is characterized by high REE abundance （∑REE = 180.2-344.3μg/g）, medium-strong negative Eu anomalies （δEu = 0.33-0.82）, weak REE fractionation [（La/Yb）N = 4.12-10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, Hf, Zr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and Ti. These characteristics of major, REE and trace elements indicate that the intrusion was formed in a transitional tectonic setting from compressionai to extensional regime, which can be classified as post-collisional granitoids. SHRIMP U-Pb zircon analyses yield ages of 517±9 and 504±8 Ma for the quartz diorite and monzogranite units, respectively. The discovery of Early Paleozoic post-collisionai granites in the northern margin of the Erguna massif indicates that the northern branch of Paleo-Asian Ocean between Siberian plate and Erguna massif was closed in the Early Paleozoic and the Salair orogeny ended ca. 500 Ma ago.     

SHRIMP zircon U-Pb dating of the Gangou granitoids, Central Tianshan Mountains, Northwest China and tectonic significances

Two types of granitoids, highly deformed eugen grenitoids end undeformed fine-grained grenitoids, ere widely distributed in Gangou area, Central Tianshen Mountains, Northwest China. The augen grenitoids are high-K calc-alkaline characterized by high K20, Rb, Y and Th, and low Sr and Sr/Y. They also have high contents of large ion lithophile elements （LILE）, such as Be, Rb, K and Th, and relatively low contents of high field strength elements （HFSE）, such as Zr, Y and Nb. The fine-grained granitoids are calc-alkaline cherecterlzed by high Sr, low Y and HREE, similar to adakitic rocks, and with Na20/K20〈2 （1.76-1.91）, high/sr （0.70689--0.70981）, and negative εNd（t） （-2.4-5.3）. High-precision SHRIMP U-Pb zircon dating results indicate that the Gangou augen greniUods were formed at 428 ± 10 Me, and the fine-grained granitoids were emplaced at 361 -368 Me. These geochemical and U-Pb zircon data have significant implications for the timing of closure of the Mishigou-Gangou Ocean and the evolution of the Central Tianshan orogenic belt.     

Zircon SIMS ages and chemical compositions from Northern Dabie Terrain: Its implication for pyroxenite genesis

We present the results of a detailed micro-scale investigation of zircons from pyroxenites, Daoshicong Northern Dabie using a combination of SIMS and ICPMS. The SIMS measurements gave ages of 134—159 Ma. Its average of (144.5± 6.2) Ma is interpreted as the best estimate of the pyroxenite intrusion. The crystallization of zircons continued for quite a long time and underwent slow cooling. The pyroxenites are products of post-collision magmatism. The REE pattern is HREE-enriched, and its HREE concentrations fall between the magmatic and metamorphic range of gneissic zircons from the Dabie area, which indicate the involvement of crust material in its mantle source.     

粤北下庄岩体岩石化学特征与铀成矿关系探讨

粤北印支期下庄岩体岩石具有富硅(SiO2 =69.13％ ～73.39％,平均值71.73％)、富碱质(K2O+ Na2O =7.49％ ～8.69％,平均值7.97％)等特征,w(K2O)/w(Na2O) ＞1,铝饱和指数(ASI)为1.01 -1.21,岩体属于高钾钙碱性及过铝质岩石系列,以上特征表明,岩体属于典型...     

西藏多巴—班戈地区燕山晚期花岗岩的成因与找矿前景

探讨西藏多巴—班戈地区燕山晚期花岗岩类岩体的成因,评价找矿前景.通过对花岗岩类岩体的地质、地球化学、成分演化程度、分异程度和氧化状态的分析,结果表明,早白垩世花岗岩的岩石组合为英云冈长岩-花岗闪长岩-二长花岗岩,属偏铝质—过铝质高钾钙碱性I型,具弱的斜长石分离结晶,形成于火山弧环境,角闪岩部分熔融而来; SiO2含量低...     

山西塔儿山—二峰山碱性偏碱性杂岩体侵入期次及岩石化学特征

通过对塔儿山—二峰山碱性偏碱性杂岩体各类岩石的野外地质特征和岩石化学研究,认为岩浆岩侵入顺序为闪长岩类→正长岩类→二长岩类→花岗岩→脉岩类。源区岩浆经历了钙碱性→偏碱性→碱性的演化系列。Al2O3、TFe2O3、Na2O＋K2O、MgO质量分数呈现与SiO2相反的演化特点。岩浆源区随岩浆演化由上地幔到地壳逐渐变浅。