The Cenomanian and Turonian in NortheasternCentral Asia

Northeastern Central Asia during the Albian and Early Cenomanianwas one of the peripheral basins of the Central Asian region. The similarity of their freshwater molluscs makes it possible to correlate isolated series in these two regions. Subsequently, a pulsating transgression of the Tadzhik Sea invaded northeastern Central Asia which became a part of the Central Asian Province of the Tethys. The complicated palaeogeography means that there are many different local biostratigraphic successions. The relations between these have been worked out from an integrated study of the biostratigraphy, palaeogeography, ecology and biogeography. Marked endemism amongst the molluscs, sometimes total, limits correlation with other regions of the Tethys; in particular, correlation of some of the local biozones (or “lones”) with western European zones is still uncertain.     

Simulation and prediction of multi-scenario evolution of ecological space based on FLUS model: A case study of the Yangtze River Economic Belt,China

Journal of Geographical Sciences - Building the Yangtze River Economic Belt (YREB) is one of China’s three national development policies in the new era. The ecological environment of the...     

40Ar/39Ar dating,fluid inclusions and S–Pb isotope systematics of the Shabaosi gold deposit,Heilongjiang Province,China

The Shabaosi deposit is the only large lode gold deposit in the northern Great Xing'an Range. The gold ore bodies are hosted by sandstone and siltstone of the Middle Jurassic Ershi'erzhan Formation, and are controlled by three N–S‐trending altered fracture zones. The gold ore bodies are composed of auriferous quartz veinlets and altered rocks. Fluid inclusion studies indicate that the ore‐forming fluids belong to a H₂O–NaCl–CO₂–CH₄ system, with salinities between 0.83 and 8.28 wt% NaCl eq., and homogenization temperatures ranging from 180 to 320 °C. The δ³⁴S values of sulphides show a large variation from −16.9‰ to 8.5‰. The Pb isotope compositions of sulphides are characterized by a narrow range of ratios: 18.289 to 18.517 for ²⁰⁶Pb/²⁰⁴Pb, 15.548 to 15.625 for ²⁰⁷Pb/²⁰⁴Pb, and 38.149 to 38.509 for ²⁰⁸Pb/²⁰⁴Pb. The μ values range from 9.36 to 9.51. These results suggest that the ore‐forming fluids/materials were mainly of magmatic hydrothermal origin, derived from magmas produced by partial melting of the lower crust. The ⁴⁰Ar/³⁹Ar age of auriferous quartz veinlets from the Shabaosi gold deposit is about 130 Ma. The Shabaosi gold deposit has counterparts in similar orogenic gold deposits, and was formed during the post‐collisional setting of the Mongolia–Okhotsk Orogen. Copyright © 2014 John Wiley & Sons, Ltd.     

The Cambrian to Aquitanian geological record of the Longi-Taormina Unit (Calabria-Peloritani Arc,southern Italy): geodynamic implications

The Longi-Taormina Unit forms the “Dorsale calcaire” of the Peloritani Alpine Belt (southern Calabria-Peloritani Arc). It is made by a thick sedimentary cover of Meso-Cenozoic age overlying a Variscan weakly metamorphosed Cambrian to Carboniferous succession.

The Palaeozoic series consists of pelitic to arenaceous sediments containing layers of acidic and basic volcanics. The acidic volcanics are affected by the “Caledonian” compressional deformations and are referred to Early Ordovician. The basic rocks belong to two different volcanic cycles; the first, not dated, is ascribed to the Caledonian cycle according to its geochemical signature; whereas the second, middle-late Devonian in age, is interpreted to have formed in the framework of pre-Variscan extensional tectonics. During the Variscan Orogeny (330 Ma), the area recorded metamorphism up to subgreenschist-to-greenschist facies and two main deformation phases, marked by syn-schistose early folds (Dv₁), overprinted by dominantly NW-SE trending late folds (Dv₂).

During the Aquitanian, deformation related to the Alpine Orogeny led to imbrication of the Palaeozoic and Meso-Cenozoic series. The sedimentary cover was affected by a series of N090° to N130° trending folds. Detailed stratigraphical and structural investigations on the tectonic contact between the Longi-Taormina Unit, and the overlying Fondachelli Unit indicate that this structure is part of a frontal thrust ramp which developed during the Aquitanian.

Our geological and structural studies on the Cambrian to Aquitanian rocks of the Longi-Taormina Unit of the Calabria-Peloritani Arc enable to unravel the complex geodynamic history of the central-western Mediterranean area.     

中亚造山带中段古亚洲洋北向平板俯冲过程:来自埃达克岩的证据

早三叠世是中亚造山带（CAOB）中部构造演化的关键时期,尽管该时期古亚洲洋在地表已经闭合,但残余的大洋板片仍在持续的挤压作用下继续俯冲,造山作用依然活跃。本文对中亚造山带中段林西地区的下三叠统幸福之路组火山岩地层进行了锆石U-Pb测年、岩石地球化学以及锆石原位Lu-Hf同位素研究。LA-ICP-MS锆石U-Pb定年结果显示了该地层的形成时代为247Ma,为早三叠世岩浆活动的产物。岩石学和地球化学研究表明,幸福之路组火山岩具有高SiO₂（64.10%~68.90%）、Al₂O₃（13.47%~17.50%）,低MgO（0.51%~1.42%）,轻稀土富集、重稀土亏损,无Eu异常（δEu平均值为1.09）以及高Sr（384×10^-6~956×10^-6,平均616×10^-6）,低Y（5.66×10^-6~7.63×10^-6,平均6.51×10^-6）的特点,表明其为大洋板片熔融产生的典型埃达克岩。锆石原位Lu-Hf同位素分析结果显示其ε_Hf（t）为+10.8~+15.6,平均为+13.9。样品单阶段Hf地壳模式年龄（t_DM1）为264~462Ma,表明其岩浆源区的亏损特征。结合区域资料,我们将研究区中晚二叠世至晚三叠世划分为四个构造演化阶段：1）中-晚二叠世时期,特征为钙碱性岩浆岩及碰撞杂岩的发育;2）早-中三叠世时期,特征为广泛分布的典型埃达克岩,是古亚洲洋地表闭合后大洋板片继续北向平板俯冲的产物;3）230Ma左右开始持续10Myr,该时期是岩浆活动宁静期;4）220Ma至晚三叠世末,研究区进入区域性伸展,A型花岗岩、富钾钙碱性花岗岩类和超基性岩大量侵位,变质核杂岩及韧性剪切带也在此时产生。前三个阶段代表了完整的古亚洲洋大洋板块平板俯冲过程,而最后一个阶段标志着研究区地壳进入了新的演化阶段。

     

老挝琅勃拉邦—泰国黎府成矿带古特提斯构造-岩浆演化与金铜成矿作用

老挝琅勃拉邦—泰国黎府成矿带位于印支板块西北缘,是中南半岛重要的金铜成矿带之一。该带经历了晚古生代—中生代古特提斯构造-岩浆演化作用,成矿活动复杂,形成了斑岩-矽卡岩型金铜矿床、浅成低温热液型金银矿床以及热液脉型金矿床。然而,热液脉型金矿的成因类型仍存在争议,3类金铜矿床与区域构造演化的关系仍缺乏总结。本文通过对前人典型矿床研究资料的整理,并结合成矿流体来源、演化新证据,将带内热液脉型金矿床的成因类型归为造山型金矿。综合区域构造-岩浆-成矿作用研究资料,总结了成矿带内3类金铜矿床的时空分布规律和成矿特征,建立了与古特提斯洋俯冲-闭合及陆陆碰撞过程相关的区域金铜成矿模式,提出了晚二叠世—早三叠世俯冲期浅成低温热液型金银矿床、早中三叠世闭合期斑岩-矽卡岩型铜金矿床、晚三叠世陆陆碰撞期造山型金矿床的成矿规律。     

秦岭造山带中秦岭群内初始北北东向构造方位及其地质意义

通过对秦岭造山带中古元古代结晶基底岩群之一-秦岭群详细的构造研究,识别出了秦岭群中存在的初始的NNE向构造方位,这一构造方位与中晚元古代以来秦岭造山带NWW向主导性构造方位大相径庭.结合区域地质背景分析,讨论了这一NNE向构造方位的地质意义.提出了古元古代华北克拉通与扬子克拉通可能为一个统一的克拉通,暂称之为古中国克拉通,并且这一克拉通内的主导性构造线方位是NNE向.中元古代初,这一克拉通沿NWW向破裂,才开始了秦岭造山带长期复杂的构造演化历史.     

Fusulinoidean faunal succession of a Paleo–Tethyan oceanic seamount in the Changning–Menglian Belt, West Yunnan, Southwest China: An overview

Abstract   Fusulinoidean faunal succession from Paleo–Tethyan seamount-type carbonates of the Yutangzhai section in the Central zone of the Changning–Menglian Belt of West Yunnan, Southwest China, is presented for the first time. The Changning–Menglian Belt is one of the orogenic belts that represent the closed main Paleo–Tethys in East Asia. The Yutangzhai section is represented by basalts and overlying carbonates, about 1100 m thick. It exhibits a continuous faunal succession composed of 17 fusulinoidean assemblages ranging from the Serpukhovian (late Mississippian/late Early Carboniferous) to Midian/Capitanian (late Middle Permian/late Guadalupian). No significant faunal break can be recognized in this section. The generic and some specific composition of the Yutangzhai assemblages indicates that the faunal succession is similar to those observed in Tethyan and Panthalassan areas and is of tropical Tethyan type although their generic diversity is definitely lower than those of Paleo–Tethyan shelves, such as South China, Indochina, and Central Asia. Throughout the Yutangzhai section, the carbonate rocks are essentially massive, very pure in composition, and devoid of terrigenous siliciclastic inputs. These lithologic characters are identical to those observed in accreted shallow-marine carbonate successions of seamount origin in Permian and Jurassic accretionary complexes of Japan, for example the Akiyoshi Limestone. This evidence further demonstrates the seamount origin of the basalt–limestone succession in the Central zone of the Changning–Menglian Belt from the viewpoint of lithofacies. In middle Mississippian (middle Early Carboniferous) time, oceanic submarine volcanism that was probably related to hot spot activities formed a number of seamounts and oceanic plateaus. It was active not only in the Panthalassa, but also in the Paleo–Tethys.     

新疆后造山碱性花岗岩的地质特征

新疆地区碱性花岗岩分布很广泛,可以划分出十条岩带,它们主要分布在古生代岛弧、弧后盆地及隆起区,与板块缝合线、深断裂密切相关,并与蛇绿岩和陆相火山岩相伴生。同位素年代测定表明,本区碱性花岗岩的形成是紧随造山运动之后发生的,属于后造山花岗岩。因此,它们形成时的构造环境、岩石化学成分、矿物组成及微量元素特征等均与非造山花岗岩（A型花岗岩）有一定的区别。在一个地区有这么多后造山碱性花岗岩分布,国内外并不多见,这是新疆地质的一个特色。     

中亚造山带中新生代壳幔相互作用特征与过程——新疆北部幔源岩浆岩系对比研究

新疆北部中新生代幔源岩浆岩多位于大型走滑断裂带或者裂谷带附近,岩石系列均具有高的TiO2含量,富碱、高度富集不相容元素和轻稀土(LREE),εNd(t)值低正值到负值,(87Sr/86Sr)i值较高,不相容元素比值La/Nb和Nb/U显示中新生代玄武岩浆在形成过程中的壳幔作用明显不同于古生代造山过程,岩浆来源于类似OIB源的富集地幔。而新疆北部地区的二叠纪幔源镁铁-超镁铁岩来源于亏损地幔,陆壳物质参与了岩浆的形成,源区可能混入了早期的弧组分或俯冲的洋壳。由于古生代多个洋盆闭合和增生造山作用致使中亚造山带的岩石圈不断增厚,于古生代晚期发生拆沉去根作用,软流圈亏损地幔上涌形成二叠纪镁铁-超镁铁岩系,而拆沉的岩石圈以及俯冲下沉的洋壳及其沉积物,在地幔环境熔融交代改造原始地幔,使中亚地区的地幔自古生代晚期以后逐渐转换为整体富碱、富含轻稀土(LREE)和不相容元素的富集地幔。被改造了的富集地幔在中新生代沿裂谷带或大型走滑断裂薄弱带上涌,形成了中新生代幔源岩浆的喷发和侵位。