Characteristics of soure region and tectonic implications of Early Indosinian Weiya gabbroic rock, eastern Tianshan mountains

Based on the detailed petrographic study, the characteristics of source region of the Weiya gabbro and tectonic implications were studied. The results show that the gabbroic rock consists mainly of gabbro, with less amount of ultra-mafic rocks. The ultra-mafic rocks show cumulate texture and are gradually transitional contact with gabbro, indicating that they are cumulate products of parental magma. The ultra-mafic rocks consist mainly of spinel periodite and spinel clinopyroxenite. The former is mainly composed of olivine （65%-70%）, spinel （10%-15%）, hornblende （5%-10%） and phlogopite （5%-10%）; the latter consists mainly of clinopyroxene （70%-80%）, spinel （15% 20%） and phlogopite （0-10%）, with minor amounts of carbonate （0-2%）. No olivine or orthopyroxene is found. The gabbro is composed mainly of clinopyroxene （35%-40%）, plagioclase （An 55-65, 40%-45%）, hornblende （5%-15%）, with variable amounts of carbonate （0-5%）. Petrographic observations show that the source region of the Weiya gabbroic rock is water-rich due to intensive intra-continental A-type subduction occurring in this region during late Permian to early Triassic.     

Zircon geochemistry of different intrusive phases of Weiya pluton, implications for magma genesis

1INTRODUCTION Ithasbeenshownthatpetrogenesisofthe granitescannotbefullyexplainedsolelybypetro graphicandgeochemicalstudies.Thisisbecausethegranitesobservedinthefieldanddisplayedby laboratoryanalysisonlyrepresentaparticularstate towardsequilibriumandtheirpresentmineralogyandchemistryartnothingbuttheultimateprod uctsofmagmaevolution.Inaddition,lithological lyvaryinggranitescanoccuratthesametectonic setting,andmineralogicallyandgeochemicallysimilargranitescanbeproducedindiverseenviron ments[1…     

坦桑尼亚Kagera地区地质成矿条件与找矿前景预测

分析坦桑尼亚Kagera地区地质成矿条件,预测找矿前景.坦桑尼亚西北部的Kagera地区,地处著名的Kibaran造山带东缘,经历了多次构造-岩浆活动,变质作用强烈,地质演化历史复杂,具备了较好的成矿条件.在Kagera地区的大岩体发现超大型的Kabanga镍矿,而且其他小的基性-超基性岩体均有矿化.区域的北部出现类似于Kabanga镍矿的较强磁异常.中西部沿石英岩和泥岩接触带出露串珠状辉长岩,辉长岩中常见石英细脉,局部见星点状黄铁矿、黄铜矿硫化物.中部发现两个大的磁异常及地球化学Ni异常.地质工作表明,Kagera地区对于寻找与正岩浆有关的铜镍硫化物矿床有较好前景.     

东天山白石头泉天河石花岗岩岩浆-热液过渡阶段的副矿物

新疆哈密星星峡白石头泉天河石花岗岩从下往上分为5个岩相带,即淡色花岗岩、含天河石花岗岩、天河石花岗岩、含黄玉天河石花岗岩和黄玉钠长花岗岩。各相带中都有一些岩浆晚期形成的不规则状孔洞。孔洞多小于2 mm,其充填物以萤石为主,并有石榴石、锡石、钠长石和白色云母等。这些充填物是岩浆-热液过渡阶段晚期的产物。充填物的成分表明,贫钙镁铁而富氟的过铝花岗岩,其岩浆-热液过渡阶段的晚期产物以含大量萤石为特征,并表明氟化物或氟络合物是该阶段流体中锡的重要搬运形式。该阶段初步富集锡的孔洞流体如因构造裂隙贯通而发生运移,就可能在有利地段聚集,形成脉状锡矿床。