恒山中东部灰色片麻岩剪切变形初探

恒山高级变质岩区是中国早前寒武纪变质岩研究的经典地区之一。通过对区内露头尺度的构造研究,识别出恒山灰色片麻岩在新太古代晚期发生了2期剪切变形,2期剪切变形形成的构造形迹在空间分布、岩石的变形习性、变形组构等方面均存在差异。重点分析了早期构造变形形成的各种构造形迹的特点,认为恒山中东部的灰色片麻岩早期形成的自北而南由网结状分布的强变形带向均匀带状展布的强变形带的变化是构造变形分解的结果,代表了岩石在中深构造层递进变形的过程,具有时空演变的意义。这一过程是由均匀的岩石、各向异性不均匀的岩石向强烈定向的岩石转变的过程。     

沙沟街地区原划秦岭群中解体出一套TTG岩系

通过对沙沟街地区商丹构造带北部原划秦岭群进行 1∶ 5万区调填图 ,从前人划分的副变质片麻岩中解体出一套变质中酸性古侵入体 - TTG岩系。划分和圈定出 5个片麻岩体 ,归并为 2个片麻杂岩 ,建立了老安子沟片麻岩套 ,并从岩石、地球化学等方面综合进行了探讨。     

大别山北部榴辉岩和英云闪长质片麻岩锆石U-Pb年龄及多期变质增生

大别山北部榴辉岩及英云闪长质片麻岩的锆石U-Pb年龄分析表明：北部榴辉岩相峰期变质时代为226～230Ma左右;北部塔儿河一带英云闪长质片麻岩经历过印支期变质事件;大别山北部与南部超高压岩石中一致的（226～230Ma）高压或超高压变质年龄表明,北部镁铁-超镁铁质岩带中部分岩石也曾作为扬子俯冲陆壳的一部分,在印支期发生过高压或超高压变质作用;本区锆石发生过两期变质增生事件,一是印支期高压或超高压变质,另一期是燕山期热变质事件;榴辉岩及英云闪长质片麻岩的原岩形成时代为晚元古代;锆石U-Pb年龄可用多期变质增生模型来解释。     

西准噶尔别鲁阿嘎希花岗闪长岩年代学、地球化学特征及岩石成因

为更深入了解西准噶尔晚古生代岩浆活动和构造背景,对位于西准噶尔中部的别鲁阿嘎希岩体开展了年代学、地球化学以及Sr-Nd同位素研究,讨论了岩石成因、源区性质和构造背景.别鲁阿嘎希花岗闪长岩为钙碱性系列岩石,岩浆锆石结晶年龄为318.7±3.3 Ma.其具相对高的MgO(Mg#=49~59)、Ni、Cr含量,富集大离子亲石元素(如K、Rb、Sr和Ba)、亏损高强场元素(如Nb、Ta、Ti),轻重稀土元素分异不明显.Sr-Nd同位素特征显示,其有较低的初始Sr比值(0.704 297~0.704 399),较高的ε_Nd(t)值(5.8~6.5).通过综合分析,认为在晚石炭世早期,达尔布特洋壳(板片)俯冲至地幔楔下部,俯冲洋壳板片脱水所产生的流体在上升过程中与地幔楔共同作用,底侵加热由亏损地幔形成不久的年轻地壳(由洋壳和岛弧组成),使其部分熔融形成了别鲁阿嘎希分异I型花岗岩.      

藏东类乌齐地区吉塘岩群的构造地层解析及主要依据

吉塘岩群沿藏东他念他翁—紫曲—吉塘一线分布,主要由片岩、片麻岩和糜棱岩组成构造岩片集合体,变形强烈,同位素年龄自古元古代—晚古生代,有必要进行解体。通过近年来的填图、测制剖面和同位素年龄的测定,并参考前人的资料及综合对比研究,对吉塘岩群(现藏东他念他翁变质杂岩体)进行了解体,将其分解为前奥陶纪—中三叠世类乌齐片麻岩套和前石炭纪吉塘岩群(>340 Ma)2套地质体。然后将类乌齐片麻岩套划分为5个构造岩石地层单元:前奥陶纪查秋赛岩组(438.2±3.6)~700.0 Ma、早二叠世都拉扎片麻岩单元(282.1±0.91)Ma、晚二叠世加压玛片麻岩单元(254.0±8.0)Ma、早三叠纪世加隆片麻岩单元(246.3±0.8)Ma、中三叠世宁达片麻岩单元(227.0±0.6)Ma。吉塘岩群的解体是该区地层研究的重要进展,有助于藏东基础地质研究。     

Distribution Characteristics and Metallogenic Regularity of Graphite Deposits in Qinling Orogen, China

Qinling orogen is one of the five main repository distribution provinces of large scale graphite resources. Graphite occurrence strata are multitudinous including Neo Archaean group to Neopaleozoic. Mineral deposit types are complete consisting of crystal flaky graphite deposit and aphanitic graphite deposit, ore types of the former are main graphite gneiss, graphite schist and graphitized marble, and ore types of the latter are main graphite layer metamorphosised from coal bed and graphitic carbargilite. At present, most graphite deposits with low research degree only implement preliminary investigations of the graphite resource, which has a good prospect. Based on the basic material of dozens of graphite deposits, spots and plays discovered in the Qinling orogen, this paper applied geologic multidisciplinary analysis method to disclose the graphite deposit types of the Qinling orogen, mainly through outdoors geologic survey and specimen examination with analysis of some typical deposits: regional metamorphism crystal graphite deposits and thermo-contact metamorphic aphanitic graphite deposits, with the control of latitudinally trending regional tectonic, graphite deposits of the Qinling orogen distribute sublatitudinally trending three large ore belts: I the Neoarchean–Proterozoic basement crystal graphite enrichment deposits zone along the south margin of North China plate; II the Carboniferous intermountain basin group aphanitic graphite enrichment deposits zone near the Shangdan suture of the West Qinling; III Paleozoic crystal graphite enrichment deposits zone in the Qinling paleomicroplate of the west part of the East Qinling.Conclusions are reached from multiple inquiries: Qinling multi-cycle complex continental collision orogen zone has experienced multiple tectonic framework transformation and polyphase tectonic thermal event from Neo Archean Erathem adjointing multiple graphite tectonic mineralization cycle. In the light of chief control of mineralization and ore types, each of the three large graphite deposits belts of the Qinling orogen has its own genesis: I graphite deposits enriched metallogenetic zone is that regional tectogenetic movement from Neo Archaean caused polyphase metapepsis, which superimposed up and reconstructed Neo Archean Erathem to Proterozoic basement, forming regional metamorphic big flake crystal graphite deposits; II graphite deposits enriched metallogenetic zone is that polyphase regional tectogenetic movement associated with multiple heating caused by multiphase igneous intrusion, which resulted in original coal layers emerging multiple thermo-contact metamorphisms and formed thermo-contact metamorphic aphanitic graphite deposits. III graphite deposits enriched metallogenetic zone is that Palaeozoic cap–rock experienced polyphase metapepsis, forming regional metamorphic finely flake crystal graphite deposits. Comprehensive research of metallogenetic mechanism in graphite deposits and its associated profitable deposits of the Qinling orogen is importance for future exploration.     

赞皇前寒武纪变质杂岩区变质反应结构与变质作用P-T-t轨迹

赞皇变质杂岩位于华北克拉通中部造山带中南段、太行山东麓低山区。出露于该变质杂岩区中南部的含石榴石的斜长角闪片麻岩、泥质片麻岩,均保存了三期矿物组合:进变质、峰期变质和退变质矿物组合。这两大类变质岩石中,进变质阶段矿物组合(M₁)以石榴石变斑晶核部的包裹体矿物组合为代表,变质高峰期矿物组合(M₂)由石榴石变斑晶"边部"和基质矿物组成,退变质阶段矿物组合(M₃)主要是环绕石榴石边部发育的"白眼圈"状后成合晶矿物组合。泥质片麻岩中的石榴石变斑晶均保存了明显的成分环带,且在边部很窄的范围内X_Mn有所增加、Mg/(Mg+Fe)有所降低,指示存在变质高峰期后的退变质过程。温度与压力计算结果表明,赞皇斜长角闪片麻岩所经历的进变质阶段(M₁)温度约为640~710℃、 压力约为8.2~8.6kbar;高峰期(M₂)变质温度超过810℃,压力大于12.1kbar;退变质阶段(M₃)的温压范围为590~670℃和3.2~5.6kbar。此前的研究已说明泥质片麻岩的进变质阶段(M₁)变质温度为660~690℃,压力为9.0~9.2kbar;高峰期(M₂)变质温度超过780℃,压力大于12.5kbar。变质高峰属于中压相系的顶部至高压相系的底部。斜长角闪片麻岩、泥质片麻岩均记录了典型的顺时针P-T轨迹,并显示近等温减压(ITD)的退变质片段。对泥质片麻岩中多颗锆石的变质增生边的SHRIMP U-Pb定年表明,变质高峰期时代为1821±17Ma。变质作用历史说明赞皇变质岩区卷入了华北克拉通东部陆块和西部陆块之间的俯冲-碰撞、随后的快速隆升过程,为华北克拉通中部造山带早元古代末期(~1850Ma)存在的造山事件提供了新的证据 。     

贺兰山北段贺兰山岩群富铝片麻岩碎屑锆石LA-ICP-MS U-Pb定年及区域对比

贺兰山北段贺兰山岩群中发育一套富铝片麻岩,Al2O3含量较高,总体与粘土质岩石化学成分相似,显示孔兹岩系的特征,变质矿物组合主要为石榴子石、堇青石、硅线石、十字石、紫苏辉石等,变质级别达角闪岩相—麻粒岩相。从宗别立岩组含石榴矽线黑云二长片麻岩中选取100粒各种类型的锆石进行了LA-ICP-MS U-Pb同位素测年,获得47个测年数据,锆石年龄多数介于1.80~2.15Ga之间,峰值为2.00~2.05Ga。碎屑锆石年龄频谱图与鄂尔多斯地块北缘的集宁岩群和乌拉山岩群十分相似,总体与吕梁构造运动的时限一致,为华北克拉通成熟陆壳演化阶段的产物,证明孔兹岩系形成于古元古代,之后长期处于稳定状态,很少受到构造热事件的干扰。     

SHRIMP U–Pb ages of ultrahigh-pressure and retrograde metamorphism of gneisses, south-western Sulu terrane, eastern China

Laser Raman spectroscopy and cathodoluminescence (CL) images reveal that most zircon separated from paragneiss and orthogneiss in drillhole CCSD‐PP2 at Donghai, south‐western Sulu terrane, retain low‐P mineral‐bearing inherited cores, ultrahigh‐pressure (UHP) mineral‐bearing mantles and low‐P mineral‐bearing (e.g. quartz) rims. SHRIMP U–Pb analyses of these zoned zircon identify three discrete and meaningful age groups: Proterozoic protolith ages (> 680 Ma) are recorded in the inherited cores, the UHP metamorphic event in the coesite‐bearing mantles occurred at 231 ± 4 Ma, and the late amphibolite facies retrogressive overprint in the quartz‐bearing rims was at 211 ± 4 Ma. Thus, Neoproterozoic supracrustal protoliths of the Sulu UHP rocks were subducted to mantle depths in the Middle Triassic, and exhumed to mid‐crustal levels in the Late Triassic. The exhumation rate deduced from the SHRIMP data and metamorphic P–T conditions is 5.0 km Ma^?1. Exhumation of the Sulu UHP terrane may have resulted from buoyancy forces after slab break‐off at mantle depths.