Purang Ultramafic Complex and Their Geological Origin, Southwest Tibet

<正>Neoproterozoic ophiolitic Serpentinites are common in the Arabian–Nubian Shield(ANS)of the Eastern Desert(ED)of Egypt,which were formed in arc stage in different tectonic setting.Thus they might subject to exchange with the crustal material derived from recycling subducting oceanic lithosphere.This caused metasomatism enriching     

Rodingite in the Purang Ophiolite and Its Geological Implication, Southwest Tibet

<正>The Yarlung Zangbo Suture Zone(YZSZ)separates the Lhasa block of the Eurasian plate to the north from the Indian plate to the south,along a~2000km discontinuous E–W trending suture zone,several heterogeneous remnants of the Neo-Tethyan oceanic floor have been preserved from the subduction recycling.The Purang ophiolite massif is one of the most spectacular exposures     

西藏普兰超镁铁岩体东部铬尖晶石矿物学特征及其地质意义

尖晶石是地幔橄榄岩中一种非常重要的矿物,虽然含量很低,却可以作为其寄主岩石——地幔橄榄岩——的成因指示剂.普兰岩体东部铬尖晶石分布广泛,几乎在所有岩石类型中都有出现.通过矿物学特征的研究,认为尖晶石可分为两类,一类较自形,颜色较深;另一类多呈不规则状和蠕虫状,颜色较浅.根据其化学特征,又可分为富铬型的尖晶石(Cr#＞60)和富铝型的尖晶石(Cr#＜60),富铬型尖晶石主要出现在纯橄岩、蛇纹岩和辉石岩中,富铝型尖晶石主要出现在二辉橄榄岩中.其中,方辉橄榄岩中的尖晶石形态、化学成分变化比较大,说明它经历了较为复杂的形成和变化过程.通过对尖晶石矿物学和化学特征的综合研究,认为该区尖晶石具有深海橄榄岩和上部俯冲板片(SSZ)构造环境橄榄岩特征,普兰岩体可能先后经历了MOR和SSZ两种构造环境.     

西藏羌塘南缘早白垩世普让岩体的锆石U-Pb年龄和地球化学特征及其地质意义

普让岩体位于西藏羌塘南缘多龙矿集区西北部,岩体的岩石类型组合为石英二长岩—二长岩—二长闪长岩,侵位于三叠纪日干配错群灰岩中,并形成矽卡岩型磁铁矿。石英二长岩LA-ICP-MS的锆石~(206)Pb/~(238)U加权平均年龄为116±2Ma(MSWD=6.5),与该带上的多龙含矿斑岩成岩年龄基本一致。普让岩体不含白云母,且标准矿物中富含透辉石,具有较高的Al_2O_3,较低的Ti O_2,富集大离子亲石元素(LILE),亏损高场强元素(HFSE)和重稀土元素(HREE),显示Nb和Ta的负异常,具有明显的岛弧型岩石的地球化学特征,属于准铝质I型花岗岩。与多龙含矿斑岩相比,普让岩体具有相似的ε_(Nd)(t)值(-7.22~-6.81),n(~(87)Sr)/n(~(86)Sr)i值(0.707525~0.708243)和古老的Nd的模式年龄(1.29~1.63Ga)。研究表明:普让岩体可能是在班公湖—怒江洋壳北向俯冲的背景下,下地壳重熔,且在上升的过程中经历了分离结晶和地壳混染作用下形成的。多龙外围的岩浆岩带不仅具有寻找斑岩铜矿的潜力,也是形成和寻找的矽卡岩型多金属矿的有利地区。     

西藏拉轨岗日核杂岩盖层变质分带特征及其地质意义

藏南拉轨岗日由一系列链状的热穹隆构成, 总体呈东西向延伸, 每一个热穹隆是一个变质核杂岩, 核部发育大量变质岩, 基底与盖层之间发育拆离断层.通过对拉轨岗日变质带及其特征变质矿物进行化学成分分析和温度压力估算, 得出拉轨岗日变质带的分带规律及矿物成分、变质温度、压力、深度的变化规律, 为拉轨岗日变质核杂岩的热活动提供了佐证.      

山东沂水麻粒岩杂岩中的变质流体及地质意义

山东沂水麻粒岩杂岩中含有大量高密度富ＣＯ＿２流体包裹体，伴随有ＣＯ＿２－Ｈ２Ｏ，ＣＯ＿２±Ｎ＿２±ｃＨ＿４的包裹体。对这些包裹体的产状、分布和组成等特征进行了详细的岩相学研究，并选择有代表性样品进行了显微测温和激光拉曼探针分析。结合本区地质和岩石学研究成果确定沂水麻粒岩杂岩峰期变质温度为８００℃，压力为０．７５ＧＰａ。对变质流体组成、演化及其成岩意义也进行了讨论。     

Modes of Occurrence and Geological Origin of Beryllium in Coals from the Pu''an Coalfield, Guizhou, Southwest China

The concentration, modes of occurrence and geological origin of beryllium in five workable coal beds from the Pu'an Coalfield of Guizhou were studied using the inductively coupled-plasma mass spectrometry (ICP-MS), floating and sinking experiments (FSE) and sequential chemical extraction procedures (SCEP). The results show that the average concentration of beryllium in coals from the Pu'an Coalfield is 1.54μg/g, much lower than that in most Chinese and worldwide coals. Beryllium in the Pu'an coals was not significantly enriched. However, it should be noted that the No. 8 coal bed from the study area has a high concentration of beryllium, 6.89μg/g, three times higher than the background value of beryllium in coal. Beryllium in coal mainly occurs as organic association and has predominantly originated from coal-forming plants when its concentration is relatively low. The concentration of beryllium occurring as organic association is close to that distributed in inorganic matter when beryllium concentration of coal is similar to its background value, and in addition to coal-forming plants, beryllium is mainly derived from detrital materials of terrigenous origin. When beryllium is anomalously enriched in coal, it mainly occurs as organic association and is derived from volcanic tonsteins leached for a long geological time and then adsorbed by organic matter in peat mire.     

Modes of Occurrence and Geological Origin of Beryllium in Coals from the Pu'an Coalfield, Guizhou, Southwest China

The concentration, modes of occurrence and geological origin of beryllium in five workable coal beds from the Pu'an Coalfield of Guizhou were studied using the inductively coupled-plasma mass spectrometry (ICP-MS), floating and sinking experiments (FSE) and sequential chemical extraction procedures (SCEP). The results show that the average concentration of beryllium in coals from the Pu'an Coalfield is 1.54μg/g, much lower than that in most Chinese and worldwide coals. Beryllium in the Pu'an coals was not significantly enriched. However, it should be noted that the No. 8 coal bed from the study area has a high concentration of beryllium, 6.89μg/g, three times higher than the background value of beryllium in coal. Beryllium in coal mainly occurs as organic association and has predominantly originated from coal-forming plants when its concentration is relatively low. The concentration of beryllium occurring as organic association is close to that distributed in inorganic matter when beryllium concentration of coal is similar to its background value, and in addition to coal-forming plants, beryllium is mainly derived from detrital materials of terrigenous origin. When beryllium is anomalously enriched in coal, it mainly occurs as organic association and is derived from volcanic tonsteins leached for a long geological time and then adsorbed by organic matter in peat mire.     

Modes of Occurrence and Geological Origin of Beryllium in Coals from the Pu''''an Coalfield, Guizhou, Southwest China

The concentration, modes of occurrence and geological origin of beryllium in five workable coal beds from the Pu'an Coalfield of Guizhou were studied using the inductively coupled-plasma mass spectrometry (ICP-MS), floating and sinking experiments (FSE) and sequential chemical extraction procedures (SCEP). The results show that the average concentration of beryllium in coals from the Pu'an Coalfield is 1.54μg/g, much lower than that in most Chinese and worldwide coals. Beryllium in the Pu'an coals was not significantly enriched. However, it should be noted that the No. 8 coal bed from the study area has a high concentration of beryllium, 6.89μg/g, three times higher than the background value of beryllium in coal. Beryllium in coal mainly occurs as organic association and has predominantly originated from coal-forming plants when its concentration is relatively low. The concentration of beryllium occurring as organic association is close to that distributed in inorganic matter when beryllium concentration of coal is similar to its background value, and in addition to coal-forming plants, beryllium is mainly derived from detrital materials of terrigenous origin. When beryllium is anomalously enriched in coal, it mainly occurs as organic association and is derived from volcanic tonsteins leached for a long geological time and then adsorbed by organic matter in peat mire.     

西藏西部普兰蛇绿岩中的MOR型辉长岩:岩石学和年代学

西藏普兰蛇绿岩位于雅鲁藏布江缝合带的西段,主要由地幔橄榄岩、辉长岩和玄武岩组成.在拉昂错南侧有一个辉长岩体,面积约1 km2,与其相邻的地幔橄榄岩为侵入接触关系.辉长岩为中细粒辉长结构,块状构造,主要矿物为半自形板柱状基性斜长石和他形-半自形粒状辉石.岩石化学成分显示其具有MOR型岩石特点,表现为中等含量的TiO2(1％～1.77％),低含量的K2O(0.08％～0.21％)和P2O5(0.1％);轻稀土元素(LREE)轻微亏损的近平坦型稀土元素球粒陨石标准化模型,(La/Ce)N、(La/Sm)N和(La/Yb)N等特征比值分别为0.73～0.80、0.44～0.58、0.53～0.65;岩石的高场强元素(HFSE)为相互平行的具有接近1的平坦型分配型式.微量元素的N-MORB标准化图解显示富集大离子亲石元素(LILE)如Rb,高场强元素(HFSE)轻微亏损.辉长岩锆石的LA-ICP-MS U-Pb年龄为130±3Ma,指示了普兰蛇绿岩形成的时代,与邻区休古嘎布、东波蛇绿岩的形成时代相一致.     

岛弧环境中不同成因的火成岩组合及其地质意义

岛弧环境的形成是与大洋板块俯冲作用有关,由俯冲流体作用于地幔楔部分熔融形成的钙碱性火成岩组合是岛弧环境中物质组成的主体。此外,目前还识别出与俯冲作用有关的其它的岩石类型:埃达克岩、富铌玄武岩、TTG、赞岐岩、玻安岩等,它们指示着不同的地球动力学背景、壳—幔相互作用过程以及源岩发生部分熔融的物理化学条件。本文主要对形成于岛弧环境中不同成因的火成岩组合的特征、形成机制、成矿作用及动力学意义进行了综述。     

藏南库局淡色花岗岩锆石U-Pb年龄、岩石地球化学特征及地质意义

库局淡色花岗岩大地构造上位于喜马拉雅特提斯造山带中东部,淡色花岗岩呈不规则状、近椭球状侵位于古生代热拉岩组中。其中白云母二长花岗岩LA-ICP-MS锆石U-Pb年龄为21±0.3Ma(MSWD=4.3),时代为中新世。岩石具有高SiO_2、富Al_2O_3与K_2O,贫CaO、MgO、TiO的特征。A/CNK=1.03～1.15(平均1.13),3属于高钾钙碱性系列过铝质岩石。稀土元素球粒陨石标准化分布曲线总体显示向右倾斜的轻稀土富集Eu亏损型。大离子亲石元素Rb、Th、U、K富集,高场强元素Nb、Ta、Zr、Ti呈现低谷负异常,显示具同碰撞S型花岗岩特征,成岩岩浆源自地壳。结合最新资料及本文研究成果,初步认为库局淡色花岗岩形成于STDS启动之后的伸展减薄背景下,为印度板块和欧亚大陆碰撞过程中地壳物质部分熔融的产物。     

西藏1∶5万班戈县西南地区四幅区调成果与展望

西藏1∶5万班戈县西南地区四幅区域地质矿产调查为青藏专项地质调查项目。该项目取得的主要成果为:1发现了区内寒武系火山岩呈角度不整合覆盖于念青唐古拉群之上,其内部划分为3个岩性段;新建了上寒武统他多雄组。2对下奥陶统扎扛组进行了解体;新建了芙蓉统龙郊组。3通过详细的地质填图,在永珠蛇绿混杂岩带中新发现一套沉积混杂岩,认为该混杂岩区域延伸稳定;新建了晚侏罗世索尔岩组。4对蛇绿岩填图单元进行了解体,由超镁铁质岩、辉长岩、席状岩墙群、枕状玄武岩岩片、放射虫硅质岩组成,新建了晚侏罗世永珠蛇绿岩群。5确定了念青唐古拉群,新识别出的变质花岗岩形成时代为中新元古代,为研究古印度地盾北缘罗迪尼亚大陆形成期和裂解期的构造热事件提供了新资料。     

Origin and age of bornhardts,Southwest Western Australia

Most of the granitic residuals of the Wheat Belt of southwestern Western Australia are bornhardts, with some nubbins developed at the western margin and occasional poorly developed castellated forms. Their origin and age can be deduced from their structure and their relationship to a weathered (lateritic) land surface and various palaeochannels. The bornhardts are massive and most stand lower than local palaeosurface remnants. They are best interpreted as having formed by differential fracture density controlled weathering beneath the weathered land surface in pre‐Eocene times. They were exposed by the stripping of the regolith beginning in the Eocene. Many are clearly stepped, indicating that their exposure took place not all at once, but episodically. A few bornhardts stand higher than the weathered land surface. They pre‐date the Eocene and the stepped morphology preserved on some suggests that their crests are much older.     

西藏尕尔穷-嘎拉勒铜金矿集区侵入岩岩石地球化学特征 及其地质意义

尕尔穷-嘎拉勒矿集区位于西藏班公湖-怒江成矿带西段,是该带上近年来取得重大勘查突破的矽卡岩(斑岩)型铜金矿集区,区内现已发现有尕尔穷及嘎拉勒两个矽卡岩型铜金矿床。区内侵入岩主要有GL(嘎拉勒)花岗闪长岩、GL花岗斑岩、GL闪长岩、GE(尕尔穷)花岗斑岩、GE石英闪长岩等燕山晚期中酸性侵入岩。地球化学特征显示,区内侵入岩SiO2含量在53.68%～80.78%之间,平均值为65.66%,Al2O3含量在8.51%～16.91%之间,A/CNK(铝饱和指数)在0.54～1.11之间,表明区内侵入岩为准铝质-弱过铝质钙碱性-高钾钙碱性岩石系列;微量元素及稀土元素地球化学特征显示,区内侵入岩相对富集大离子亲石元素Rb、Sr、Th,而亏损Ta、Nb、Hf、Zr、Yb、Ti等高场强元素,各岩石类型均具Nb、Ta、Ti负异常,其中GE花岗斑岩具有非常明显的亏损Sr和Ti的特征。岩石成因类型判别表明GE花岗斑岩为S型花岗岩,而其它岩类为I型花岗岩,结合构造环境的判别,指示矿集区侵入岩形成于班公湖-怒江特提斯洋闭合后碰撞隆升阶段。     

西藏定结、定日一带上石炭统纳兴组重力流沉积及其地质意义

西藏定结、定日一带上石炭统纳兴组为一套厚度巨大的陆源碎屑沉积, 该组中部首次识别出重力流沉积.重力流沉积可划分为3个类型: 崩塌沉积、碎屑流沉积和浊流沉积, 以碎屑流沉积常见.通过沉积相和基于沉积物组分及地球化学方面的物源分析, 判断该区晚石炭世存在小型洼陷盆地, 其形成与晚石炭世海西伸展运动有关, 纳兴组重力流沉积与下伏滨浅海沉积之间具一伸展不整合.      

Mineralogy of Purang Ophiolite Peridotites, Western Part of Yarlung-Zangbo Suture Zone (YZSZ), Southern Tibet

<正>The Purang ophiolite is a large mantle peridotite massif ca.600 km~2 in area.The mantle peridotite is composed dominantly of harzburgite,lherzolite and minor dunite.The Fo and NiO contents of olivine in the peridotites are in the range of 89.5~92.8 and 0.23~0.44 wt.%,respectively;both of these parameters increase gradually