新疆东天山晚古生代地壳增生和成矿作用

地壳增生和成矿作用是矿床学研究的前沿领域;东天山作为中亚造山带的重要组成部分,在晚古生代地壳演化过程中经历了板块俯冲、碰撞造山大规模走滑剪切和后造山演化阶段,在每个构造演化阶段都伴随有地壳增生和大量有用金属元素的堆积。按照地壳增生和成矿作用关系,研究区晚古生代主要有如下几种矿床类型:1)晚泥盆世—早石炭世增生前形成的Cu-Mo-Au-Ag矿床;2)早石炭世增生前形成的Fe-Cu-Pb-Zn矿床;3)晚石炭世—早二叠世增生后形成的造山型Cu-Ni-PGE矿床;4)晚石炭世—早二叠世增生后形成的造山型Au-Cu矿床。上述矿床在形成过程中既有地壳的水平增生,也有地壳的垂向增生作用,已经构成了我国重要的内生金属矿床富集区。     

Early Paleozoic Magmatism and Gold Mineralization in the Northern Altun, NW China

This paper discusses the relationships between granitic magmatism and gold mineralization and the exhumation history of the Dapinggou gold deposit in northern Altun, NW China based on the geochronological data, including zircon U-Pb ages, Rb-Sr isochron age and 40Ar-39Ar dating and MDD modeling data. The main granitic magmatism age in this area is attained from the ID TIMS U-Pb geochronology of zircons from the Kuoshibulak granite, the biggest granite in the northern Altun area, which gives a concordant age of 443±5 Ma in the Late Ordovician. Zircon ID TIMS U-Pb geochronology of the West Dapinggou biotite granite west of the Dapinggou gold deposit gives concordant ages around 485±10 Ma, representing the early stage of Ordovician magmatism. The Rb-Sr isochron age (487±21 Ma) of 6 quartz inclusion samples from quartz veins in this gold deposit is very close to that of the West Dapinggou granite. MDD modeling of step heating 40Ar-39Ar data of K-feldspar from the same West Dapinggou biotite granite gives     

Early Paleozoic Magmatism and Gold Mineralization in the Northern Aitun, NW China

Abstract This paper discusses the relationships between granitic magmatism and gold mineralization and the exhumation history of the Dapinggou gold deposit in northern Altun, NW China based on the geochronological data, including zircon U‐Pb ages, Rb‐Sr isochron age and ⁴⁰Ar‐³⁹Ar dating and MDD modeling data. The main granitic magmatism age in this area is attained from the ID TIMS U‐Pb geochronology of zircons from the Kuoshibulak granite, the biggest granite in the northern Altun area, which gives a concordant age of 443±5 Ma in the Late Ordovician. Zircon ID TIMS U‐Pb geochronology of the West Dapinggou biotite granite west of the Dapinggou gold deposit gives concordant ages around 485±10 Ma, representing the early stage of Ordovician magmatism. The Rb‐Sr isochron age (487±21 Ma) of 6 quartz inclusion samples from quartz veins in this gold deposit is very close to that of the West Dapinggou granite. MDD modeling of step heating ⁴⁰Ar‐³⁹Ar data of K‐feldspar from the same West Dapinggou biotite granite gives a rapid cooling history from 300°C to 150°C during 200–185 Ma. According to the age data and the geological setting of this area, we conclude that the Dapinggou gold deposit was formed at the early stage of the Early Paleozoic granitic magmatism in northern Altun, and exhumed in the Early Jurassic due to the normal faulting of the Lapeiquan detachment. The Early Paleozoic magmatism may provide heat source and produce geological fluids, which are very important for gold mineralization. Exhumation in the Mesozoic caused the uplift of the deposit towards the ground surface.     

柴达木盆地北缘古生代超高压带中花岗质岩浆作用

祁连南缘古生代超高压变质带 (榴辉岩年龄为 4 6 6～ 4 95 Ma)上一套中高级变质岩系 (达肯大坂片麻岩 )中存在三类花岗岩组合 : 类 :石英二长闪长岩 -花岗闪长岩 -二长花岗岩 , 类 :二长花岗岩 -二云母花岗岩-含白云母花岗岩 -正长花岗岩 , 类 :花岗闪长岩 -二长花岗岩 -黑云母花岗岩。 类岩石组合中的二长花岗岩锆石SHRIMP年龄为 4 73Ma, 类岩石组合中的正长花岗岩锆石 SHRIMP年龄为 4 4 6 Ma, 类岩石组合中的二长花岗岩锆石 SHRIMP年龄为 397Ma。从三类花岗岩组合的组成矿物来看 , 类和 类的矿物组合主要为斜长石、角闪石、石英、碱性长石、黑云母 , 类的矿物组合为钾长石、石英、白云母、黑云母、斜长石 ;从岩石地球化学特征上看 , 类和 类花岗岩为 型花岗岩 ,岩石的 Si O2 =6 1%～ 6 9% ,Na2 O/ K2 O>1,ANK<1,δEu=0 .7～ 1.0 ; 类花岗岩为 S型花岗岩 ,岩石的 Si O2 =70 %～ 76 % ,Na2 O/ K2 O<1,ANK>1,δEu=0 .1～ 0 .3;从构造环境上看 , 类花岗岩形成于岛弧环境或活动大陆边缘 , 类花岗岩形成于同碰撞 , 类花岗岩形成于碰撞后。结合区域地质特征 ,我们认为 ,早奥陶世 ,南祁连洋板块向北俯冲于祁连陆块之下 ,规模不大的南祁连洋很快闭合 ,但俯冲下去的大洋板块仍拖动柴达木陆块继续俯冲 ,俯冲     

Discovery of Early Paleozoic Garnet Amphibolite in theWenquan Complex,Northern Margin of the Yili Block,NW China

Objective High-pressure(HP)and ultrahigh-pressure(UHP)minerals tend to be preserved in mafic and ultramafic metamorphic rocks(e.g.eclogites and garnet amphiboli...     

Thermochronology of allochthonous terranes in Ecuador: Unravelling the accretionary and post-accretionary history of the Northern Andes

The western cordilleras of the Northern Andes (north of 5°S) are constructed from allochthonous terranes floored by oceanic crust. We present ⁴⁰Ar/³⁹Ar and fission-track data from the Cordillera Occidental and Amotape Complex of Ecuador that probably constrain the time of terrane collision and post-accretionary tectonism in the western Andes. The data record cooling rates of 80–2 °C/my from temperatures of 540 °C, during 85 to 60 Ma, in a highly tectonised mélange (Pujilí unit) at the continent–ocean suture and in the northern Amotape Complex. The rates were highest during 85–80 Ma and decelerated towards 60 Ma. Cooling was a consequence of exhumation of the continental margin, which probably occurred in response to the accretion of the presently juxtaposing Pallatanga Terrane. The northern Amotape Complex and the Pujilí unit may have formed part of a single, regional scale, tectonic mélange that started to develop at ~85 Ma, part of which currently comprises the basement of the Interandean Depression. Cooling and rotation in the allochthonous, continental, Amotape Complex and along parts of the continent–ocean suture during 43–29 Ma, record the second accretionary phase, during which the Macuchi Island Arc system collided with the Pallatanga Terrane. Distinct periods of regional scale cooling in the Cordillera Occidental at 13 and 9 Ma were synchronous with exhumation in the Cordillera Real and were probably driven by the collision of the Carnegie Ridge with the Ecuador Trench. Finally, late Miocene–Pliocene reactivation of the Chimbo–Toachi Shear Zone was coincident with the formation of the oldest basins in the Interandean Depression and probably formed part of a transcurrent or thrust system that was responsible for the inception and subsequent growth of the valley since 6 Ma.     

秦岭晚古生代弧前增生的背驮型盆地体系

秦岭发育了受断裂控制的晚古生代沉积盆地,其基底是具有洋壳、众多碳酸盐岩孤岛以及岛弧、弧前增生楔的洋盆底;盆地的主要边界逆冲断裂表现为背驮式的活动特征;各个盆地虽都有自己的沉积特点,但盆地的相对水深总体由北向南逐渐加大,反映出弧前大陆斜坡的地理特征;盆地初始规模较大,到后期渐小,盆地充填呈退积序列,揭示了秦岭晚古生代盆地具有弧前增生的背驮型盆地性质。     

藏北羌塘中部晚古生代增生杂岩的发现及其地质意义

西藏中部羌塘变质岩带发育复理石碎屑建造和片理化玄武岩建造,都经历了强烈的构造置换作用;还发育早—晚古生代大理岩岩片、无根勾状褶皱和大理岩与蓝片岩组成的同斜褶皱,不同时代的榴辉岩呈岩块出露。这些地质体呈岩片产出,经历了多期构造叠加和置换,原岩总体为碎屑岩、泥质岩、硅质岩、碳酸盐岩及枕状玄武岩、辉长岩建造。宏观上发育明显的区域性置换面理,为典型的造山带增生杂岩。     

藏北羌塘中部晚古生代增生杂岩的发现及其地质意义

西藏中部羌塘变质岩带发育复理石碎屑建造和片理化玄武岩建造,都经历了强烈的构造置换作用;还发育早—晚古生代大理岩岩片、无根勾状褶皱和大理岩与蓝片岩组成的同斜褶皱,不同时代的榴辉岩呈岩块出露。这些地质体呈岩片产出,经历了多期构造叠加和置换,原岩总体为碎屑岩、泥质岩、硅质岩、碳酸盐岩及枕状玄武岩、辉长岩建造。宏观上发育明显的区域性置换面理,为典型的造山带增生杂岩。     

Meso-Cenozoic extensional structures in the Northern Tarim Basin, NW China

Meso-Cenozoic extensional structures are important for understanding the tectonics of the Chinese Central Asia. This paper presents a systematic investigation on the Meso-Cenozoic extensional structures in the Northern Tarim Basin. Close interpretations of seismic data reveal that the Meso-Cenozoic extensional structures were widely developed in the Northern Tarim Basin. These extensional structures are regionally composed of many small normal faults, which usually group into left- or right-step en echelon and form several transtensional fault zones. Combinations of normal faults in profile become small graben-horst or staircase-like cross-sections. Based on the areal distribution, structural style, combination relationship, formation and evolution time, and formation mechanism of the extensional structures, we found that the Meso-Cenozoic extensional structures in Northern Tarim Basin can be classified into two conjugate normal fault systems, which were formed separately in Jurassic-Early Cretaceous and Late Cretaceous-Neogene. The former is likely associated with the stress relaxation after a collisional orogeny accompanied with a certain degree of anticlockwise rotation of the Tarim block relative to the South Tianshan; the latter is possibly induced by the east by south tectonic escape of the Tarim block with a certain degree of clockwise rotation relative to the South Tianshan triggered by the far-field effect of the Himalayan orogeny.     

Kinematics and age constraints of deformation in a Late Carboniferous accretionary complex in Western Junggar,NW China

The Karamay area, situated in the eastern part of Western Junggar, Southern Altaids, contains an ophiolitic mélange with ultramafic rocks, gabbro, basalt, chert and limestone, which show typical block-in-matrix structures, and coherent turbidites and tuffs. These lithological associations are interpreted as incoherent and coherent series formed in an accretionary complex. On the basis of detailed field mapping and analyses of the asymmetry of imbricate thrusts, duplexes, tilted structures, shear band cleavages, and the NW-verging inclined to overturned folds, we conclude that the overall movement in the accretionary complex was top-to-the-NW. The youngest tuff involved in the deformation contains detrital zircons that have a U–Pb age (LA-MC ICP-MS) of 308 ± 7 Ma. ³⁹Ar–⁴⁰Ar resistance furnace step-heating of amphibole separates from a diorite dike, which cuts the folded and imbricated rocks in the accretionary prism, yielded a plateau age of 307 ± 2 Ma. Consequently, the age of the deformation in the prism is tightly constrained at 307–308 Ma, implying that the deformation occurred in an extremely short time-span during SE-ward subduction. Combined contemporaneous occurrence of Baogutu adakite, high-Mg, Sr-enriched and Y-poor dioritic dikes, Miaoergou charnockite, and Maliya mafic rocks, we further suggest the accretionary complex was cut by near-trench volcanic rocks and plutons possibly due to interaction with a spreading ridge.     

新疆东部新元古代晚期和古生代构造格局及其演变

基于笔者近20年来对新疆东部地质构造的研究和对前人地质地球物理资料的深入分析，本文系统讨论了新疆东部新元古代晚期和古生代的地壳形成与演化。该区古生代的构造单元被划分为阿尔泰地块、额尔齐斯断裂带、东准噶尔古生代造山带、准噶尔地块、东天山造山带和库鲁克塔格地块。该区古生代地壳构造演化包括震旦纪-石炭纪洋陆格局的变迁、石炭纪末至二叠纪后碰撞壳幔相互作用等两个阶段。其洋陆格局的变迁包括古生代早期萨彦洋、早古生代阿尔曼太尔洋、晚古生代卡拉麦里洋、古生代北天山洋和南天山洋的打开与关闭，其中两个天山洋盆可能为一个洋盆，大体上可以对比为中亚地区的古亚洲洋北支斋桑洋，阿尔曼太洋和卡拉麦里洋可能为西伯利亚古陆的边缘洋盆；而古亚洲洋南支的乌拉尔一南天山洋向东是否延伸到新疆东部，还有待于进一步研究。新疆东部的后碰撞构造演化包括三期重大地质事件：①300Ma前后的以中酸性为主的大规模岩浆活动；②280Ma前后的包括幔源岩浆在内的双峰式岩浆活动；⑧二叠纪中晚期(可能延续到三叠纪)的大规模地壳走滑运动。在此基础上，对新疆东部新元古代晚期和古生代构造演化与古亚洲洋演变的关系进行了探讨，并对仍然存在的主要相关问题进行了总结和归纳。     

南祁连拉脊山口增生楔的结构与组成特征

造山带内增生楔/增生杂岩结构与组成的精细研究可为古洋盆演化和古板块构造格局重建提供最直接证据。北祁连构造带发育多条增生杂岩带,记录了阿拉善和中祁连地块之间原特提斯洋的俯冲和闭合过程,然而南祁连构造带大地构造演化长期存在争议。地质填图结果表明,南祁连构造带拉脊山口地区存在一套强烈片理化的玄武岩、灰黑色和红色硅质岩、砂岩和泥岩组合,它们与一套呈现"块体裹夹于基质"结构特征的混杂岩共同构成了增生杂岩,发育双重逆冲构造、逆冲断层、无根褶皱、紧闭褶皱和透入性面理。该增生杂岩与蛇绿岩之间为断层接触,并位于断层下盘。混杂岩是由斜长花岗岩(561Ma)、斜长岩(507Ma)、辉绿岩、玄武岩、硅质岩和砂岩等外来或原地岩块与浊流成因的细碎屑岩基质共同组成;基质和砂岩块体均发育同沉积构造,呈现出滑塌堆积典型特征。空间上,拉脊山口增生杂岩与上覆蛇绿岩被断层所分割且共同仰冲于中祁连南缘青石坡组浊积岩之上,具有与东侧昂思多地区增生杂岩和蛇绿岩相似的岩石组成、构造变形和时空结构特征。它们与南侧的岛弧带共同构成了南祁连构造带寒武纪-早奥陶世沟-弧体系,指示了寒武纪-早奥陶世时期南祁连洋盆向南俯冲。     

华北地区古生界海相油气潜力分析

华北地区自早元古代结晶基底形成以后的沉积盖层发育演化可划分为五个阶段:拗拉槽—克拉通边缘(Pt_2—Pt_3);克拉通—被动大陆边缘(∈—T_1);裂谷盆地(T_2—K);拉张断陷盆地(E);坳陷盆地(N—Q)。中、上元古界—古生界海相碳酸盐岩和碎屑岩为该区海相油气勘探提供了多套勘探层系和广阔空间,并以二次生烃(再生烃)为特征,构成再生烃油气系统。海相油气勘探的有利地区,一般古生界保存完好,二次生烃强度大,且为晚期成藏。划分出了13个古生界二次生烃的有利区块,它们一般位于中一新生代沉积凹陷区,海相烃源岩主要为奥陶系碳酸盐岩和石炭系一二叠系煤系地层,二次生烃强度在5×10~8～70×10~8 m~3/km~2范围。作为多种沉积盆地类型并存的叠合盆地,具有多旋回构造运动、多套生储盖组合、多阶段生烃的特征,使同一区域内有多种油气系统的叠合,构成复合油气系统。区内存在古生古储再生烃油气系统、古生新储再生烃油气系统、新生古储油气系统等几种基本类型的油气系统。对华北地区海相油气的勘探应重视印支运动和燕山运动的破坏作用及后期沉降导致的二次生烃作用,尤其是在中—古生界地腹保存较完整、且晚白垩世—早第三纪再次埋藏发生二次生烃作用的地区应该具有良好的勘探前景,是天然气勘探的重要地区。     

Geology of Qiaoxiahala Fe-Cu-Au Deposit: A Paleozoic IOCG Deposit in Altaids, NW China

Please?refer?to?the?attachment(s)?for?more?details.     

Paleozoic magmatic events in the Strandja Massif,NW Turkey

The Strandja massif consists of metamorphic basement intruded by large Early Permian plutons of the Kirklareli type and overlain by Triassic metasedimentary cover. Together with its continuation in Bulgaria this massif forms an important link between the Pontides and the orogenic belts of Europe. Various types of orthogneisses constitute a significant part of the metamorphic basement however these rocks have until now escaped a particular study and therefore the Paleozoic history of the massif is essentially unknown. In this study these rocks are classified and mapped as hornblende-biotite, biotite-muscovite, and leucocratic orthogneisses. Their modal compositions correspond to quartz diorite, tonalite, granodiorite and trondhjemite. Geochemical data suggest a calc-alkaline trend of differentiation and metaluminous character of the parent magmas. Isotopic dating using the single zircon evaporation method has shown that magmatic ages of these orthogneisses cluster within a short time interval between 312±2 and 315 ±5 Ma in the Carboniferous. At the same time inherited ages of magmatic zircons in these rocks record a long lived magmatic activity between 340 and 650 Ma. We infer that the Carboniferous orthogneisses were formed in a magmatic arc that evolved atop of a mature continental basement. Previously established ([1, 2]) Early Permian magmatic event has been confirmed by additional age determinations constraining it at 257±6 Ma. Tectonic setting of this episode is also interpreted as subduction related taking into consideration its geochemical features and relationships with surrounding tectonic units.     

Early Paleozoic accretionary orogens along the Western Gondwana margin

Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension and back-arc basin development.The southwestern margin is represented by Famatinian and Pampean basement realms exposed in South America,both related to the protracted Paleozoic evolution of the Terra Australis Orogen,whereas the northwestern margin is mainly recorded in Cadomian domains of Europe and adjacent regions.However,no clear relationships between these regions were so far established.Based on a compilation and reevaluation of geological,paleomagnetic,petrological,geochronological and isotopic evidence,this contribution focuses on crustal-scale tectonic and geodynamic processes occurring in Western Gondwana accretionary orogens,aiming at disentangling their common Early Paleozoic evolution.Data show that accretionary orogens were dominated by high-temperature/lowpressure metamorphism and relatively high geothermal gradients,resulting from the development of extended/hyperextended margins and bulk transtensional deformation.In this sense,retreating-mode accretionary orogens characterized the Early Paleozoic Gondwana margin,though short-lived pulses of compression/transpression also occurred.The existence of retreating subduction zones favoured mantle-derived magmatism and mixing with relatively young(meta)sedimentary sources in a thin continental crust.Crustal reworking of previous forearc sequences due to trenchward arc migration thus took place through assimilation and anatexis in the arc/back-arc regions.Therefore,retreating-mode accretionary orogens were the locus of Early Paleozoic crustal growth in Western Gondwana,intimately associated with major flare-up events,such as those related to the Cadomian and Famatian arcs.Slab roll back,probably resulting from decreasing convergence rates and plate velocities after Gondwana assembly,was a key factor for orogen-scale geodynamic processes.Coupled with synchronous oblique subduction and crustal-scale dextral deformation,slab roll back might trigger toroidal mantle flow,thus accounting for bulk dextral transtension,back-arc extension/transtension and a large-scale anticlockwise rotation of Gondwana mainland.     

新疆中天山古生代侵入岩浆序列及构造演化

新疆中天山构造岩浆带是中亚造山带的重要组成部分,广泛分布着古生代花岗质侵入体。本研究重点对中天山南缘巴音布鲁克及巴伦台地区的花岗质侵入体进行了LA-ICP-MS锆石U-Pb测年,并获得了岩体侵位年龄由老到新分别为463±3Ma(石英闪长岩)、437±5Ma(石英闪长岩)、424±3Ma(二长花岗岩)、383±4Ma(二长花岗岩)、356±3Ma(二长花岗岩)和303±5Ma(正长花岗岩)。综合区域地质分析认为,中天山古生代侵入岩浆活动可分为四个构造岩浆演化阶段:(1)晚寒武世—晚奥陶世阶段,Terskey洋盆和南天山洋盆自新元古代打开形成广阔洋盆,Terskey洋盆在晚寒武世开始初次俯冲,于晚奥陶世洋盆闭合,南天山洋盆于早奥陶世初次俯冲,具有自西向东、由早到晚的俯冲特点;(2)早志留世—中泥盆世阶段,南天山洋盆持续向北俯冲,该阶段北天山洋开始向南侧俯冲,在伊犁地块北缘形成了弧岩浆;(3)晚泥盆世—早石炭世阶段,南天山洋盆闭合于晚泥盆世末期,在早石炭世中晚期进入残余洋盆演化阶段;(4)晚石炭世—早二叠世阶段,该阶段为后碰撞伸展环境,区域上为陆内演化阶段。     

华北晚古生代煤系古地理演化

根据华北晚古生代沉积岩系的环境标志，识别出29个相，归并为冲积扇，河流、三角洲、潮汐砂滩、碳酸盐台地等6个沉积体系。系统总结了华北晚古生代岩相古地理时空演化规律和沉积体系分布规律。