Late Proterozoic Colisional Orogen and Geosuture in Southeastern China：Petrological Evidence

The Jiangshan-Shaoxing fracture belt(JSFB)is a Late Proterozoic geosuture due to island arc-continent collision in South China,The Cathaysian Block(CT),lying on the southeast side of JSFB,is composed of green schist-amphibolite complexes in the form of a series of tectonic flakes. On the northwest side of JSFB,which is located in the border area of Zheijiang,Jiangxi and Ahhhi provinces(abbreviated as ZJP-JXP-AHP),are distrbuted and ophiolite suite and other rocks,constituting the Jiangnan ancient island arc(JN)on the southeast margin of the Yangtze Block(YZ).The collision between JN and CT at-0.9Ga ago led to the folding of JN.followed by the intrusion(-0.9-0.8Ga ago)of many dioritic and ultramafic stitching plutons along the fracture belt.As a result,the basic Precambrian tectonic framework of southeastern China was shaped.     

Geochemistry and petrogenesis of Cretaceous oceanic plateau lavas in eastern Jamaica

Basaltic lavas of Turonian to Coniacian age belonging to the Bath–Dunrobin Formation occur with intercalated island arc tuffs in the south of the Blue Mountain inlier, have been interpreted as being derived from the Caribbean oceanic plateau. This study presents new major and trace element and Sr–Pb–Nd–Hf isotopic data for these igneous rocks. The Jamaican rocks are altered by tropical weathering, hydrothermal and metamorphic processes, which have mobilised many of their elements (e.g. K and Ba). Consequently, the basalts and dacitic tuffs have been classified by using immobile trace elements. The trace element and _Hf(i)–_Nd(i) geochemistry suggests that the basaltic lavas are derived from a chemically similar source region by variable degrees of partial melting. The Caribbean plateau basalts lie on a mixing line between a depleted plume component and HIMU in Nd–Hf isotopic space. The Pb isotope data also demonstrate that the Jamaican plateau lavas are composed of a larger HIMU component than the other plateau lavas within the Caribbean region. The intercalated island arc tuffs are the first to be found in any oceanic plateau succession in the Caribbean and imply that the Caribbean oceanic plateau at  90 Ma was relatively close to the subduction zone along South America and the Great Arc of the Antilles.     

新疆胜利达坂地区花岗岩类的地球化学及成岩环境

岩石学、地球化学和同位素地质年代学研究表明，中天山构造带北缘胜利达坂地区的花岗岩类至少是两期岩浆活动的产物，胜利达坂岩体形成于加里东晚期的岛弧构造环境，红色钾长花岗岩形成于华力西晚期，属造山期后花岗岩。     

从岛弧向裂谷的变迁—来自阿吾拉勒地区火山岩的证据

阿吾拉勒地区早、中石炭世火山岩以碱性系列为主，少部分属钙碱性系列；稀土元素具有岛弧和活动陆缘区橄榄安粗岩和高钾安山岩的特征：微量元素具有大陆型岛弧火山岩的特征。由此证明本区在早、中石炭世处于内弧环境。二叠纪火山岩属碱性系列；稀土元素和微量元素明显有板内碱性玄武岩的特征。     

北疆地区阿尔曼太蛇绿岩锆石SHRIMP年龄及其大地构造意义

东准噶尔带阿尔曼太蛇绿岩是中亚造山带南部的重要构造单元,记录了古亚洲洋的演化,但其时代一直是学术界争论的焦点问题之一。本文报道阿尔曼太蛇绿岩中斜长花岗岩锆石SHRIMPU-Pb年龄。9组测试数据给出了较好的206Pb/238U年龄503±7Ma(MSWD=1.2)。结合相关大地构造解剖与前人的年龄数据,本文认为阿尔曼太蛇绿岩是古亚洲洋在晚寒武世-早奥陶世的残余,与岛弧火山岩组成洋内弧。该洋内弧向北拼贴到阿尔泰地体南缘,形成科迪勒拉型俯冲边缘。东准噶尔带是阿尔泰南缘在古生代向南增生的弧碰撞-增生造山带,对大陆侧向增生具有重要意义。     

北阿尔金拉配泉地区齐勒萨依岩体的年代学、地球化学特征及其构造意义

阿尔金北缘拉配泉地区的齐勒萨依岩体主要由辉长岩、闪长岩组成。地球化学特征表明,辉长岩具有高的Al2O3(13.47%~15.34%)、FeOT含量(10.77%~16.89%)以及中等的MgO含量(5.15%~7.49%);闪长岩属钙碱性系列,具有较低SiO2含量(52.06%~54.23%)和高的Mg#值(56.43~62.45)。二者在球粒陨石标准化稀土元素配分曲线上呈REE近平坦型或者LREE轻微富集型,均显示Eu弱的亏损或富集。在原始地幔标准化蛛网图上,二者均富集Rb、Ba等大离子亲石元素(LILE),相对亏损Nb、Ta、Zr和Hf等高场强元素(HFSE),具明显消减带岩浆岩的特征。辉长岩和闪长岩的锆石LA-ICP-MS U-Pb定年结果分别为477.5±3.3 Ma和469.7±3.4 Ma,表明它们属于早中奥陶世岩浆活动的产物。结合岩石的地球化学、微量元素构造环境判别图解、年代学和区域地质背景的特征,判定齐勒萨依岩体形成于与俯冲有关的活动陆缘弧的构造环境,二者的侵位与阿尔金北缘早古生代的古大洋向南俯冲消减到米兰河-金雁山活动陆缘地块之下密切相关,从而为北阿尔金早中奥陶世的陆缘弧和红柳沟-拉配泉蛇绿混杂岩带俯冲极性的进一步确定提供了佐证。     

新疆苏海图地区火山岩地球化学特征及构造环境分析

苏海图组火山岩发育自然铜矿化,具有从拉斑玄武岩系列向钙碱性玄武岩系列过渡的特点。依据地球化学特征,表明其TiO2含量较低(1%),玄武岩高的Al2O3含量、低的稀土含量,并且稀土元素曲线具有平缓型到轻稀土低度富集的特点。微量元素原始地幔标准化图解上,它们均富集大离子亲石因素(LILE),亏损高场强元素(HFSE),具有强的Nb和Ta的负异常,Ti的低负异常,以及P和Sm的低正异常。Zr/Nb值和Sm/Nd值接近MORB的范围,Th/Nb值大于0.11,Nb/Zr值小于0.04。以上这些特征均显示出典型岛弧岩浆的特点。所以,苏海图组火山岩为火山弧火山岩,其构造背景为大陆岛弧,源区可能为被流体或沉积物交待改造的亏损地幔。     

五台地区雁门关早元古代镁铁-超镁铁岩体的岩石地球化学特征、成因及其大地构造意义

本文对五台地区侵入于原北金岗库组的雁门关镁铁-超镁铁岩体进行了详细的岩石学、矿物学和岩石地球化学分析研究.雁门关岩体在矿物成份上,特别是单斜辉石、尖晶石和角闪石,具有阿拉斯加型侵入岩体和俯冲带或弧相关的岩浆特征,其元素地球化学特征也可与阿拉斯加型侵入杂岩体类比,具有明显的Nd (Ta),Zr (Hf),Y和Ti负异常.从构造环境判别图来看,雁门关岩体主要为与俯冲相关的成因,具大陆边缘弧的性质.因此,雁门关岩体是侵入在大陆边缘弧环境的岩浆经历了橄榄石和单斜辉石的分离结晶作用的产物.它与恒山-五台-阜平地区广泛分布的同时代花岗岩和火山岩一起,构成了华北克拉通中部造山带内一期重要的古元古代大陆边缘岛弧岩浆活动.     

Volcanism in Sanjiang Tethyan Orogenic Belt:New Facts and Concepts

Sanjiang area in Southwestern China is tectonically sit-uated at the east end of Himalaya-Tethys tectonic do-main and at the conjunction of Tethyan MountainChain and Circum-Pacific Mountain Chain.It is one ofthe key areas to understand the global tectonics and alsoone of gigantic metallogenic provinces in China and evenin the world.Volcanism had occurred during the periodof time from Proterozoic to Cenozoic.The most impor-tant and active periods of volcanism,however,areCarboniferous,Permian and Triassic.The pattern ofspatial distribution of Sanjiang volcanic rocks andophiolites can essentially be described as that severalintra——continental micro-massif volcanic districts arerespectively sandwiched between each two of four couplingophiolite—are volcanic belts,which are successively fromwest to east:Dingqing-Nujiang belt,Laneangjiangbelt,Jinshajiang belt and Ganzi-Litang belt.Fourtectono-magmatic types of volcanic rocks have been recognized in Sanjiang area as follows:mid-ocean-ridge/para-mid-ocean-rid     

湘西雪峰地区金多金属成矿带研究进展

对湘西雪峰地区金多金属矿床的成矿物质来源、成矿时代及控矿构造等方面的成果进行了总结,认为该区金多金属成矿带为一控矿构造复杂,具有多期、多源特征的复成矿带,NE、NW、EW和SN向构造及其次级构造为该区重要的控矿构造,存在赋矿地层、下伏更老的结晶基底以及后期含矿热液等多种成矿物质来源,加里东期和印支期可能为该区重要的金多金属成矿期.这对于全面了解雪峰地区的成矿作用有一定的参考意义.