松辽盆地形成、发展与岩石圈动力学

根据区域构造环境、深部构造机制、火山活动的时间序列以及盆地几何学、运动学特征,分析了松辽盆地形成与发展的岩石圈动力学问题。提出古太平洋板块向欧亚大陆下俯冲引起热流上升,由此导致裂谷期前火山作用和岩石圈热与机械减薄,裂谷期上地壳伸展发育成裂谷盆地,火山活动减弱。随着陆缘陆块拼贴,俯冲带长距离后退,处于热异常的岩石圈开始向热平衡转化,盆地由伸展转化为坳陷。     

松辽盆地形成与演化的深部作用过程--中生代火山岩探针

松辽盆地中生代火山作用从一个侧面揭示了松辽盆地形成与演化历史。松辽盆地中生代火山岩的岩石地球化学研究表明，中生代火山作用的深部过程表现为岩浆源区从逐渐上升到下降的过程。晚侏罗世到早白垩世早期为降温降压过程，表现为等温面逐渐升高，岩石圈伸展速度增大，岩浆源区变浅，盆地演化由断焰向坳陷转化。从早白垩世早期到晚白垩世，则为升温升压过程，等温面下降，岩石圈伸展速度变小，岩浆源区加深，盆地演化进入坳陷期。     

新生代黄骅坳陷构造伸展、沉积作用和岩浆活动

黄骅坳陷是一典型的张性盆地,其构造主要受西缘向东倾的拆离断层的控制。构造沉降分析显示盆地西部以裂谷沉降为主,而向东热沉降逐渐增大,反映了上地壳的强烈裂谷区与岩石圈深部强烈减薄区发生了错位。沉积作用在裂谷期和热沉降期具明显不同的特点,指示了早期基底快速不均匀的下沉和晚期基底广泛缓慢下沉的过程。玄武岩的形成和演化也与盆地构造发展过程相一致。研究结果表明,黄骅坳陷是在下伏岩石圈上部发生简单剪切和下部发生纯剪切的构造伸展过程中形成的。     

祁连山新元古代中—晚期至早古生代火山作用与构造演化

祁连山地区的新元古代中—晚期至早古生代火山作用显示系统地时、空变化,其乃是祁连山构造演化的火山响应。随着祁连山构造演化从Rodinia超大陆裂谷化—裂解,经早古生代大洋打开、扩张、洋壳俯冲和弧后伸展,直至洋盆闭合、弧-陆碰撞和陆-陆碰撞,火山作用也逐渐从裂谷和大陆溢流玄武质喷发,经大洋中脊型、岛弧和弧后盆地火山活动,转变为碰撞后裂谷式喷发。850~604 Ma的大陆裂谷和大陆溢流熔岩主要分布于祁连和柴达木陆块。从大约550 Ma至446 Ma,在北祁连和南祁连洋-沟-弧-盆系中广泛发育大洋中脊型、岛弧和弧后盆地型熔岩。与此同时,在祁连陆块中部,发育约522~442 Ma的陆内裂谷火山作用。早古生代洋盆于奥陶纪末(约446 Ma)闭合。随后,从约445 Ma至约428 Ma,于祁连陆块北缘发育碰撞后火山活动。此种时-空变异对形成祁连山的深部地球动力学过程提供了重要约束。该过程包括:(1)地幔柱或超级地幔柱上涌,导致Rodinia超大陆发生裂谷化、裂解、早古生代大洋打开、扩张、俯冲,并伴随岛弧形成;(2)俯冲的大洋板片回转,致使弧后伸展,进而形成弧后盆地;(3)洋盆闭合、板片断离,继而发生软流圈上涌,诱发碰撞后火山活动。晚志留世至早泥盆世(420~400 Ma),先期俯冲的地壳物质折返,发生强烈的造山活动。400 Ma后,山体垮塌、岩石圈伸展,相应发生碰撞后花岗质侵入活动。     

从地壳上地幔构造看大陆岩石圈伸展与裂解

本篇讨论大陆岩石圈拆沉、伸展与裂解作用过程。由于大陆岩石圈厚度大而且很不均匀,产生裂谷的机制比较复杂。大陆碰撞远程效应的触发,岩石圈拆沉,以及板块运动的不规则性和地球应力场方向转折,都可能产生岩石圈断裂和大陆裂谷。岩石圈拆沉为在重力作用下"去陆根"的作用过程,演化过程可分为大陆根拆离、地壳伸展和岩石圈地幔整体破裂三个阶段。大陆碰撞带、俯冲的大陆和大洋板块、克拉通区域岩石圈,都可能产生岩石圈拆沉。大陆岩石圈调查表明,拉张区可见地壳伸展、岩石圈拆离、软流圈上拱和热沉降;它们是大陆岩石圈伸展与裂解早期的主要表现。从初始拉张的盆岭省到成熟的张裂省,拆离后地壳伸展成复式地堑,下地壳幔源玄武岩浆侵位,断裂带贯通并切穿整个岩石圈,表明地壳伸展进入成熟阶段。中国东北松辽盆地和西欧北海盆地曾处于成熟的张裂省。岩石圈破裂为岩浆侵位提供了阻力很小的通道网。岩浆侵位作用伴随岩石圈破裂和热流体上涌,成熟的张裂省可发展成大陆裂谷。多数的大陆裂谷带并没有发展成威尔逊裂谷带和洋中脊,普通的大陆裂谷要演化为威尔逊裂谷带,必须有来自软流圈的长期和持续的热流和玄武质岩浆的供应。威尔逊裂谷带岩石圈地幔和软流圈为地震低速带,其根源可能与来自地幔底部的地幔热羽流有关。     

新生代黄骅坳陷构造伸展,沉积作用和岩浆活动

黄骅坳陷是一典型的张性盆地，其构造主要受西缘向东倾的拆离断层的控制。构造沉降分析显示盆地西部以裂谷沉降为主，而向东热沉降逐渐增大，反映了上地壳的强烈裂谷区与岩石圈深部强烈减薄区发生了错位。沉积作用在裂谷期和热沉降期具明显不同的特点，指示了早期基底快速不均匀的下沉和晚期基底广泛缓慢下沉的过程。玄武岩的形成和演化也与盆地构造发展过程相一致。研究结果表明，其骅坳陷是在下伏岩石圈上部发生简单剪切和下部发生     

松辽盆地裂谷期前火山岩与裂谷盆地关系及动力学过程

松辽盆地存在裂谷期前火山岩,之后上地壳脆性伸展发育半地堑裂谷盆地。裂谷期前火山岩近水平展布于基底之上,裂谷期,沉则分布于半地暂内,两者属于不同构造层。     

松辽盆地北部姚家组底部不整合面的发育特征及形成机制初探

松辽盆地北部姚家组底部的不整合面（T_1-1界面）为区域性不整合面,这一不整合面标志的隆升事件不仅控制了地层分布和层序划分,而且把盆地的坳陷阶段分为湖侵特征各不相同的两个亚阶段.姚一段的剥蚀区主要见于松辽盆地的东部和北部,反映造成这一隆升的挤压应力场来自其东南,与东亚大陆边缘移置地体的拼贴有关.松辽盆地是一个与燕山造山作用耦合发育的内陆盆地,坳陷（裂后热沉降）阶段的盆地发育受制于两个造山作用：西侧大兴安岭的热隆升和其东的东亚大陆边缘的地体拼贴引起的斜向汇聚-剪切造山作用.     

大杨树盆地的构造特征及变形期次

大杨树盆地是叠置于大兴安岭造山带的东部,与松辽盆地紧邻,呈北北东向长条带状展布的中新生代断陷-坳陷型盆地。大杨树盆地经历了多期变形作用,具有以伸展构造为主、并被挤压构造和反转构造叠加的构造特征。早白垩世龙江期主要受到了NWW—SEE向的拉伸作用,形成一系列北北东向控陷犁式正断层组合,在控陷断层的上盘发育小型箕状断陷;早白垩世九峰山期,大杨树盆地受挤压作用控制,使早期形成的断陷盆地发生反转作用,形成正反转构造,同时在某些地段形成逆冲断层和断层传播褶皱;早白垩世甘河期,大杨树盆地再次受到伸展作用,形成了一系列北北东向小型断陷。早白垩世晚期(甘河期之后)—晚白垩世早期,大杨树盆地受到强烈的挤压作用,使早期控陷正断层出现正反转作用,在盆地的浅部形成大型断层传播褶皱,使大杨树盆地全面隆升遭受剥蚀。第四纪大杨树盆地具有伸展的特征,发育一系列小型伸展断陷。     

大陆边缘扩张型活动带火山岩组合——松辽盆地周边中生代火山岩研究

松辽盆地周边中生代火山岩高峰期为Ｊ３—Ｋ１，与煤系地层共生，距古俯冲带１０００～２０００ｋｍ。盆地东侧（Ⅰ带）、西南端（Ⅱ带）、西侧（Ⅲ带和Ⅳ带）火山岩，均以高钾钙碱系列为主，少数为钾玄岩系列和钙碱系列，主要岩石组合为钾质粗面玄武岩－钾玄岩－安粗岩－粗面岩－粗面安山岩－高钾流纹岩。火山岩的地球化学特征显示出造山带火山岩之属性，但又有别于俯冲带弧火山岩；火山岩同位素比值显示中等Ｓｒ、低Ｎｄ及源区无洋壳组分参与等特征。故而认为松辽盆地周边中生代火山岩形成于叠加陆缘活动带，是岩石圈调整过程中伸展构造背景下的产物，而不是太平洋板块俯冲的直接产物。可称为大陆边缘扩张型活动带的火山岩组合。     

论中国东北大陆裂谷系的形成与演化

自中生代末期以来,东北地区形成了以松辽地堑为主体,联合下辽河裂谷、伊通-依兰裂谷、抚顺-密山裂谷以及邻近断陷盆地的大陆裂谷系,并向南北两端延伸,在亚洲东部构成一条大的裂谷带。这个大陆裂谷系的形成和发展是由中央向两侧展开的,与板块俯冲、弧后扩张密切相关。     

North‐eastward subduction followed by slab detachment to explain ophiolite obduction and Early Miocene volcanism in Northland,New Zealand

Oligocene–Miocene models for northern New Zealand, involving south‐westward subduction to explain Early Miocene Northland volcanism, do not fit within the regional Southwest Pacific tectonic framework. A new model is proposed, which comprises a north‐east‐dipping South Loyalty basin slab that retreated south‐westward in the Eocene–earliest Miocene and was continuous with the north‐east‐dipping subduction zone of New Caledonia. In the latest Oligocene, the trench reached the Northland passive margin, which was pulled it into the mantle by the slab, resulting in obduction of the Northland allochthon. During and after obduction, the slab detached from the unsubductable continental lithosphere, inducing widespread calc‐alkaline volcanism in Northland. The new model further explains contemporaneous arc volcanism along the Northland Plateau Seamount Chain and sinking of the Northland basement, followed by uplift and extension in Northland.     

Geochemistry and tectonic significance of mafic volcanic rocks of the Hindoli belt, southeastern Rajasthan: Implications for continent assembly

Mafic volcanic rocks that occur within the sedimentary pile of the Hindoli Group were analyzed for major and trace elements (including REE) to establish tectonic setting of volcanism during the early Proterozoic history of the North Indian Craton. The mafic volcanics are sub-alkaline showing compositional variation from picrobasalt to basalt. They are LREE enriched with (La/Yb)_N ratio ranging from 4.67?C6.19 (avg.5.27) and exhibit slightly concave REE patterns relative to chondrite. The multi-element patterns of these mafic volcanic rocks display relative enrichment in Th and LREE and negative anomalies of Nb and P. These geochemical characteristics are consistent with a subduction related origin. Various variation diagrams, involving immobile trace elements, distinguish the Hindoli lavas as arc basalt. However, their Ti and Nb contents are higher than those of subduction related magmas. Probably the wedge melting, along with mixing of rising asthenosphere might have produced these characteristics. It is suggested that the Hindoli basin originated by rifting of island- arc lithosphere, caused by rising plume in an extensional back arc region. Based on the results of the present geochemical study, it is proposed that in the early Proterozoic the Mewar block had an active-type continental margin on its present eastern side. The continental magmatic arcs and intra-arc basins developed on this margin were subsequently incorporated into the Mewar protocontinent. Possibly, the plate carrying the Bundelkhand block subducted beneath the eastern margin of the Mewar block, resulting in the final amalgamation of the two blocks along Great Boundary Fault zone or Banas Dislocation Zone. The arc related volcanism of north Indian shield at about 1850?C1832 Ma, appears to represent the global subduction event, which resulted in the amalgamation and formation of Columbia supercontinent.     

中国东部及邻区早白垩世裂陷盆地构造演化阶段

早白垩世是中国东部及邻区强烈的伸展裂陷和岩石圈减薄时期。根据裂陷盆地几何形态特征和展布型式 ,将早白垩世裂陷盆地分为泛裂陷型 (燕山—松辽断陷盆地群、蒙古断陷盆地群等 )、狭窄型 (沂沭裂谷系、伊兰—伊通裂谷带 )和菱形状型 (胶莱盆地、三江盆地、鸡西盆地等 ) 3种类型。通过综合分析和对比不同类型裂陷盆地沉积序列和构造演化历史 ,结合郯庐断裂带和秦岭—大别造山带白垩纪构造演化历史的研究成果 ,区分了中国东部早白垩世 2个显著不同的引张裂陷阶段和一个构造挤压反转阶段。早白垩世早期引张裂陷阶段 ( 1 4 0～ 1 2 0Ma)形成了宽广展布的燕山—松辽断陷盆地系和蒙古断陷盆地系 ,沿郯庐断裂带发生右旋走滑活动 ,控制了断裂带西侧南华北伸展走滑盆地和东侧胶莱、三江等和沿敦—密断裂带走滑拉分盆地的发育 ;早白垩世中期引张裂陷阶段 ( 1 2 0～ 1 0 0Ma) ,沿郯庐断裂带中、北段发生裂谷作用 ,形成沂沭裂谷系和伊兰—伊通裂谷带 ;早白垩世晚期 ( 1 0 0～ 90Ma)在区域NW SE向挤压应力场作用下 ,所有早白垩世裂陷盆地发生不同程度的构造反转 ,沿郯庐断裂发生强烈的左旋走滑运动。最后指出 ,太平洋古板块向东亚大陆边缘俯冲诱发的大陆岩石圈底侵作用、拆沉作用、地幔底辟和对流 ,以及来自西部块体     

Tectonostratigraphic evolution of Cenozoic marginal basin and continental margin successions in the Bone Mountains,Southwest Sulawesi,Indonesia

The Bone Mountains, located in Southwest Sulawesi along the SE margin of Sundaland, are composed of Oligocene to possibly lower Miocene marginal basin successions (Bone Group) that are juxtaposed against continental margin assemblages of Eocene–Miocene age (Salokalupang Group). Three distinct units make up the latter: (i) Middle–Upper Eocene volcaniclastic sediments with volcanic and limestone intercalations in the upper part (Matajang Formation), reflecting a period of arc volcanism and carbonate development along the Sundaland margin; (ii) a well-bedded series of Oligocene calc-arenites (Karopa Formation), deposited in a passive margin environment following cessation of volcanic activity, and (iii) a series of Lower–Middle Miocene sedimentary rocks, in part turbiditic, which interfinger in the upper part with volcaniclastic and volcanic rocks of potassic affinity (Baco Formation), formed in an extensional regime without subduction.The Bone Group consists of MORB-like volcanics, showing weak to moderate subduction signatures (Kalamiseng Formation), and a series of interbedded hemipelagic mudstones and volcanics (Deko Formation). The Deko volcanics are in part subduction-related and in part formed from melting of a basaltic precursor in the overriding crust. We postulate that the Bone Group rocks formed in a transtensional marginal basin bordered by a transform passive margin to the west (Sundaland) and by a newly initiated westerly-dipping subduction zone on its eastern side.Around 14–13 Ma an extensional tectonic event began in SW Sulawesi, characterized by widespread block-faulting and the onset of potassic volcanism. It reached its peak about 1 Ma year later with the juxtaposition of the Bone Group against the Salokalupang Group along a major strike-slip fault (Walanae Fault Zone). The latter group was sliced up in variously-sized fragments, tilted and locally folded. Potassic volcanism continued up to the end of the Pliocene, and locally into the Quaternary.     

CENOZOIC VOLCANISM AND LITHOSPHERETECTONIC EVOLUTION IN NORTH TIBET

CENOZOIC VOLCANISM AND LITHOSPHERETECTONIC EVOLUTION IN NORTH TIBET     

Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea)

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. The eastern Korean margin is rimmed by fundamental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau that is a continental fragment extended and partially segmented from the Korean Peninsula. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and considerably symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions for rifting are recognized: the Onnuri and Hupo Basins were rifted in the east-west direction; the Bandal Basin in the east–west and northwest–southeast directions, suggesting two rift stages. We interpret that the east–west direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated southeastward repeatedly from the Japan Basin toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed the direction to the south, resulting in east–west extension to create the rift basins at the Korean margin. The northwest–southeast direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the Korea Plateau; after breakup the southwestern Japan Arc separated in the southeast direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the northwest direction. No significant volcanism was involved in initial rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.     

AN INTRACONTINENTAL EXTENSIONAL TECTONIC SETTING FOR THE ORIGIN OF YULONG PORPHYRY COPPER DEPOSIT IN EAST TIBET

AN INTRACONTINENTAL EXTENSIONAL TECTONIC SETTING FOR THE ORIGIN OF YULONG PORPHYRY COPPER DEPOSIT IN EAST TIBET     

Tectonics and sedimentation of SW Sarawak basin,Malaysia, NW Borneo

Structurally SW Sarawak basin is a southward sloping basement characterized by passive margin tectonic that has undergone through varioius tectonic phases viz., Triassic extension, Cretaceous transpression and Oligo-Miocene compression. Rock types and sedimentation of deeper basin zone situated between Schwaner mountains block to the south and SW Sarawak basin to the north suggest progressive marine sedimentation. E-W trending Cretaceous carbonate platform (CCP) occurs in the SW Sarawak basin signify a shelf zone where shallow marine sedimentation progressed during Cretaceous transpression. Oligo-Miocene volcanics from subduction melts intercepted basin profusely forming northwest-southeast trending continental arc zone derived from partial melting of subducting slab underneath SW Sarawak basin. Back-arc extension prevailed during Oligo-Miocene and formed several extensional features. Oligo-Miocene subduction also resulted in closure and exhumation of Sri Aman marginal sea-basin to the east. SW Sarawak basin is further divided in two sub-basins viz., Senibong to the west and Kuching to the east separated by a northeast trending morphotectonic ridge that signify structural element formed due to shearing. Marine sedimentation progressed in these sub-basins mainly during Triassic–Jurassic while tidal and fluviatile sedimentation progressed during early to mid-Tertiary having total thickness of sediments about 9 km. Basin closure and exhumation is marked mainly by the formation of Cretaceous carbonate build-up that has been intruded and dissected by the Oligo-Miocene volcanics. Senibong and Kuching sub-basins are characterized by wide range of transpressive features, while, Sri Aman marginal sea-basin is characterized by oceanic assemblages, ophiolite, serpentinite and pillow basalt.