Australian palaeomagnetism and the Phanerozoic plate tectonics of eastern Gondwanaland

All palaeomagnetic investigations from the Phanerozoic of Australia are summarized and critically reviewed. Some smaller studies have been combined to produce more viable palaeomagnetic poles all of which are only considered if standard cleaning procedures were used. Analysis of the resulting data shows that during the Early Palaeozoic the pole paths for northern and central Australia are similar confirming the regions were a single unit during that time. However, these paths and the one derived from a limited region of southeast Australia approach each other from opposite directions and appear to converge during the Devonian. This observation is consistent with interpretations of the geology of the Tasman Orogenic Zone in terms of plate-tectonic models and with palaeomagnetic data from the Gondwanic continents. The presence of possible ancient plate margins bounding the region, from which most palaeomagnetic results from southeast Australia are derived, confirms that this region only became welded to the main Australian plate in Devonian times. Data for the Mesozoic of southeast Australia continue to be incompatible both with the generally accepted Australia—Antarctica relationship and with all other Gondwanic results. There appears to be no geological evidence in support of the large-scale relative motion inferred by the data and they remain a puzzling inconsistency. Cenozoic results, however, are entirely compatible with the northward motion of Australia away from Antarctica as inferred from sea-floor spreading. Comparisons with results from India suggest that the drift history of India prior to 75 m.y. ago involved movement from a location adjacent to Antarctica. It is proposed that the Wharton Basin was occupied by a northerly extension of Peninsular India which lay adjacent to western Australia. This larger Indian subcontinent broke away from both Antarctica and Australia about 140 m.y. ago.     

Phanerozoic history of Western Australia related to continental drift

From north to south, the sedimentary basins of Western Australia change from broad platforms of wholly marine strata that span the entire Phanerozoic (Bonaparte Gulf and Canning Basins) through the intermediate Carnarvon Basin to rifts of nonmarine Permian and Mesozoic strata (Perth Basin). These contrasts in age, facies, and structure reflect different positions of the basins in Gondwanaland: the Bonaparte Gulf and Canning Basins have lain at the continental margin facing an open ocean during the entire Phanerozoic, whereas the Perth Basin lay in the interior of Gondwanaland until India and Australia moved apart in the Cretaceous.

The Eucla Basin came about by events connected with the dispersal of Antarctica and Australia in the Eocene. The northwest part of the Australian Block (Timor and the Timor Sea) was deformed in the Miocene when Australia collided with southeast Asia.     

辽宁查马屯铁矿三维地质建模及深部预测

查马屯铁矿是一处隐伏于中生代火山沉积岩之下的沉积变质型铁矿床，矿体规模大、埋藏浅，深部资源潜力巨大.利用三维地质体建模软件Creatar，通过收集钻孔数据，建立地质数据库，生成三维钻孔.通过剖面定义、单工程矿体圈定、剖面编辑、曲面连接，建立矿体三维模型.依据"点-线-面-体"的思路，建立了辽宁查马屯铁矿三维地质模型.模型显示，查马屯铁矿体西南段向北西倾斜，北东部向南东倾斜，呈北东东向展布，应沿该方向部署找矿.矿体与磁异常复合关系表明，2号矿体南部存在巨大找矿空间，查马屯村南部及北东部是下一步找矿勘探的重点方向.     

Cretaceous–Tertiary convergence and continental collision,Sanandaj–Sirjan Zone,western Iran

The Sanandaj–Sirjan Zone contains the metamorphic core of the Zagros continental collision zone in western Iran. The zone has been subdivided into the following from southwest to northeast: an outer belt of imbricate thrust slices (radiolarite, Bisotun, ophiolite and marginal sub-zones, which consist of Mesozoic deep-marine sediments, shallow-marine carbonates, oceanic crust and volcanic arc, respectively) and an inner complexly deformed sub-zone (late Palaeozoic–Mesozoic passive margin succession). Rifting and sea-floor spreading of Tethys occurred in the Permian to Triassic but in the Sanandaj–Sirjan Zone extension-related successions are mainly of Late Triassic age. Subduction of Tethyan sea floor in the Late Jurassic to Cretaceous produced deformation, metamorphism and unconformities in the marginal and complexly deformed sub-zones. Deformation climaxed in the Late Cretaceous when a major southwest-vergent fold belt formed associated with greenschist facies metamorphism and post-dated by abundant Palaeogene granitic plutons. In the southwest of the zone a Late Cretaceous island arc—passive margin collision occurred with ophiolite emplacement onto the northern Arabian margin similar to that in Oman. Final closure of Tethys was not completed until the Miocene when Central Iran collided with the northeast Arabian margin.     

辽宁查马屯铁矿三维地质建模及深部预测

查马屯铁矿是一处隐伏于中生代火山沉积岩之下的沉积变质型铁矿床,矿体规模大、埋藏浅,深部资源潜力巨大.利用三维地质体建模软件Creatar,通过收集钻孔数据,建立地质数据库,生成三维钻孔.通过剖面定义、单工程矿体圈定、剖面编辑、曲面连接,建立矿体三维模型.依据"点-线-面-体"的思路,建立了辽宁查马屯铁矿三维地质模型.模型显示,查马屯铁矿体西南段向北西倾斜,北东部向南东倾斜,呈北东东向展布,应沿该方向部署找矿.矿体与磁异常复合关系表明,2号矿体南部存在巨大找矿空间,查马屯村南部及北东部是下一步找矿勘探的重点方向.     

华北地块北缘及邻区显生宙构造应力场

华北地块北缘及邻区显生宙不同时期存在不同类型的造山作用，古生代以陆缘俯冲造山为主，中生代以陆内挤压造山为主，新生代以陆内伸展造山为主。不同造山阶段存在不同的区域构造应力场。晚古生代陆缘俯冲造山阶段，区域最大主压应力方向以近南北向为主。中生代陆内挤压造山阶段，南北向边界挤压力的作用不断减弱，而北西—北西西向边界挤压力的作用不断增强；在中东地段，印支期—早燕山期—晚燕山期，区域最大主压应力方向发生自南北向—北西向—北西西向规律性变化。新生代陆内伸展造山阶段，区域最大主压应力方向以北东向为主。不同造山阶段区域构造应力的量值也存在明显差别，构造应力大小与造山作用强度、构造—岩浆活动性存在良好正相关关系     

西北地区45a来降水异常的时空变化及其标度特征

利用西北地区(73°~113°E,30°~50°N)157个气象站的1960—2004年日降水观测资料,通过非参数趋势检测和旋转主成分分析方法对年降水异常的时空特征进行研究.根据降水特征的差异,西北地区可以划分为西北东北部、东南部、西北部、西南部、中北部及中南部等6大区域.结果表明:西北地区降水自东南向西北逐步递减,降水变化趋势则是东南为负、西北为正,变化幅度东南大于西北.根据每个分区的降水序列标度特征,采用消除波动趋势分析方法,对6个分区45 a来降水时间序列所纪录的大气动力过程影响的时空差异进行分析,定量区分区域气候系统和局地要素对不同区域降水贡献的差异及其年代际变化.     

Variable hangingwall palaeotransport during Silurian and Devonian thrusting in the western Lachlan Fold Belt: Missing gold lodes,synchronous Melbourne Trough sedimentation and Grampians Group fold interference

The western margin of the Lachlan Fold Belt contains early ductile and brittle structures that formed during northeast‐southwest and east‐west compression, followed by reactivation related to sinistral wrenching. At Stawell all of these structural features (and the associated gold lodes) are dismembered by a complex array of later northwest‐, north‐ and northeast‐dipping faults. Detailed underground structural analysis has identified northwest‐trending mid‐Devonian thrusts (Tabberabberan) that post‐date Early Devonian plutonism and have a top‐to‐the‐southwest transport. Deformation associated with the initial stages of dismemberment occurred along an earlier array of faults that trend southwest‐northeast (or east‐west) and dip to the northwest (or north). The initial transport of the units in the hangingwall of these fault structures was top‐to‐the‐southeast. ‘Missing’ gold lodes were discovered beneath the Magdala orebody by reconstructing a displacement history that involved a combination of transport vectors (top‐to‐the‐southeast and top‐to‐the‐southwest). Fold interference structures in the adjacent Silurian Grampians Group provide further evidence for at least two almost orthogonal shortening regimes, post the mid‐Silurian. Overprinting relationships, and correlation with synchronous sedimentation in the Melbourne Trough, indicates that the early fault structures are mid‐ to late‐Silurian in age (Ludlow: ca 420–414 Ma). These atypical southeast‐vergent structures have regional extent and separate significant northeast‐southwest shortening that occurred in the mid‐Devonian (‘Tabberabberan orogeny’) and Late Ordovician (‘Benambran orogeny’).     

浙西北地区反转构造初步研究

通过浙西北地区金衢、乌马和杭嘉湖3个地震解译剖面及地表地质的综合分析,指出研究区在以T₂为主变形期的逆冲变形体制之前存在同方向的引张体制,并随后发生反转。通过计算反转比等综合分析,发现其总体反转程度自南东往北西方向逐渐变小,反映出反转后的褶皱冲断变形程度呈现自南东往北西方向变弱之趋势。     

Petrogenesis of Indosinian Granitoids in Middle-Segment of South Qinling Tectonic Belt: Constraints from Sr-Nd Isotopic Systematics

South Qinling Tectonic Belt (SQTB) is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures. There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui granitoid plutons at the northeast, Huayang-Wulong-Laocheng granitoid plutons at the central part, Xiba granitoid pluton at the northwest and Guangtoushan-Liuba granitoid plutons at the southwest. These Indonisian granitoids contain a mass of various scale mafic enclaves, which show sometimes clear boundaries and sometimes transitional boundaries with their host granitoids. These granitoids also exhibit metaluminous to peraluminous series, commonly higher Mg# and a wide range of petrochemistry from low-K tholeiite series, through mid-K and high-K calc-alkaline series to shoshonite series and predominated samples are attributed to mid-K and high-K calc-alkaline series. Detailed analyses in Sr-Nd isotopic systematics and petrochemistry reveal that there may be regionally initial granitoid magma of the Indonisian granitoid plutons, comprising Dongjiangkou-Zhashui, Huayang-Wulong-Laocheng, Xiba, and Guangtoushan-Liuba granitoid plutons, which were produced by hybrids of magmas in various degrees, and the initial magmas were derived from both the mantle and the lower continental crust (LCC) sources in the SQTB. The initial granitoid magma further did the magma hybrid with the magmas from the LCC, crystallization fractionation, and assimilation with upper crustal materials during their emplacement to produce these granitoid plutons in the SQTB. These magmatism processes are most likely to occur under continent marginal arc and syn-collision to post-collision tectonic backgrounds.     

Fission track thermotectonic imaging of the Australian continent

Fission track analyses of apatites from a very large data set across Australia provide a first look at the patterns of low-temperature thermochronology over an entire continent. The rock samples are mostly of granitic rocks, or their metamorphic equivalents, of Palaeozoic or older age from the exposed basement regions. Sample chemical analyses indicate that the apatite suite is overwhelmingly of fluorapatite composition. Approximately 2750 fission track analyses have been completed, of which >1700 are of sufficient quality to form a coherent data set that can be interpolated to show the variation of central fission track age and mean confined track length on a continental scale. The resulting images exhibit some features which are well known, such as the trend towards young apatite ages along the eastern and southeastern rifted continental margins, but others that are more surprising, such as the lack of clear differentiation, in terms of the range of ages and lengths, between the older Precambrian cratonic areas in the west, and younger Phanerozoic mobile belts to the east. The Precambrian rocks from the western two-thirds of the continent do, however, show distinctly different cooling histories to those in the eastern Phanerozoic mobile belts when the relationships between track lengths and fission track ages are considered. The western craton everywhere shows patterns of prolonged slow cooling, whereas all major regions of the eastern part of the continent show discrete episodes of rapid cooling, mostly from the Jurassic to the Palaeogene. Significant areas of unusually young apatite ages (<50 Ma) are found in Tasmania and in Precambrian rocks from the northern Gawler Block in South Australia. The most obvious regional cause of the overall fission track patterns across Australia is variation in surface denudation over time scales of hundreds of Ma. However, in some areas, such as the northern Gawler Block, other mechanisms such as the movement of hydrothermal fluids in former cover sequences must be invoked.     

鄂尔多斯盆地西南部上三叠统延长组长8、长6油层组 的沉积体系与物源方向

野外露头剖面的岩石学与岩相组合,沉积特征与相标志,古流向测定,室内砂岩的骨架矿物、重矿物组合及其平面分布规律的研究结果表明：鄂尔多斯盆地西南部上三叠统延长组长8油层组是以线状或点状物源为特征的一套近源快速堆积的冲积扇与扇三角洲沉积体系,形成于盆地由快速拗陷转入逆冲负荷沉降期间。长8沉积期盆地西南部的古水流与物源主要来自盆地西南方向,其次为西北和东南方向。长6油层组沉积期,盆地内部底床下沉作用减缓,湖盆开始收缩,湖盆西岸除北部有少量扇三角洲沉积外,主要为辫状河三角洲沉积：而盆地东北部与东部的沉积作用大大加强,致使在盆地东部形成一系列大型曲流河三角洲沉积体系,至盆地西南部相变为半深湖-深湖相与浊流相沉积。长6沉积期古水流除来自西南、西北和东南方向外．还有来自北东和正东方向的次要物源,它们在盆地西南部悦乐-玄马-板桥-固城-合水-带汇合,使该地带成为混合物源区。     

溪洛渡地区节理构造特征及解析

运用构造解析方法，遵循共轭节理配套原则对溪洛渡地区发育的次生节理构造进行逐步分析，将该区发育的北东向和北西向节理、近南北向和近东西向节理、倾向南东和北西的两组北东－南西向剖面节理、北东东向和北北东向节理以及倾向北东和南西的两组北西－南东向剖面节理组成5套共轭节理，分属南北向、北东向和北西向3个构造期次。据此推出该区次生节理的形成、发育先后受到该区南北向、北东向和北西向构造期构造应力场作用的影响和制约。     

鄂尔多斯盆地西南部上三叠统延长组长8、长6油层组的沉积体系与物源方向

野外露头剖面的岩石学与岩相组合,沉积特征与相标志,古流向测定,室内砂岩的骨架矿物、重矿物组合及其平面分布规律的研究结果表明：鄂尔多斯盆地西南部上三叠统延长组长8油层组是以线状或点状物源为特征的一套近源快速堆积的冲积扇与扇三角洲沉积体系,形成于盆地由快速拗陷转入逆冲负荷沉降期间。长8沉积期盆地西南部的古水流与物源主要来自盆地西南方向,其次为西北和东南方向。长6油层组沉积期,盆地内部底床下沉作用减缓,湖盆开始收缩,湖盆西岸除北部有少量扇三角洲沉积外,主要为辫状河三角洲沉积：而盆地东北部与东部的沉积作用大大加强,致使在盆地东部形成一系列大型曲流河三角洲沉积体系,至盆地西南部相变为半深湖-深湖相与浊流相沉积。长6沉积期古水流除来自西南、西北和东南方向外．还有来自北东和正东方向的次要物源,它们在盆地西南部悦乐-玄马-板桥-固城-合水-带汇合,使该地带成为混合物源区。     

昆仑多岛弧盆系及泛华夏大陆的增生

自从Rodinia超大陆在晚元古代解体之后,冈瓦纳大陆群与泛华夏大陆群间从晚元古代至中生代始终存在一大洋-特提斯洋。从早古生代至中生代,特提斯洋分三个阶段向泛华夏陆块群俯冲,形成了弧后扩张、弧陆碰撞和弧前增生。弧后盆地扩张到达小洋盆,出现蛇绿混杂岩。由于早期大陆边缘已向南发生了增生,继后的弧后扩张和前锋弧的位置也就相应地向南迁移了。因而蛇绿岩带、岩浆岩带会出现多条,且从北向南时代有从老变新的趋势。由于陆缘向南裂离,并到达高纬度位置,或者如洋岛的生成,随着洋壳的消减速、俯冲,高纬度的沉积体向低纬度的不断增生,这样就出现了生物的冷暖型混生。且从泛华夏陆块群或从冈瓦纳大陆群裂离的块体不能越过大洋中脊拼合在另一大陆块体上。因此,泛华夏大陆的西南缘-昆仑带只是在弧后海底扩张、弧-弧碰撞、弧-陆碰撞的多岛弧造山作用、向南不断增生过程中形成的。     

A tectonic escape model for the formation of sedimentary basins in the Yangzhou block of the Lower Yangtze Region,Eastern China

This paper presents a tectonic escape model for the formation of sedimentary basins in the Yangzhou Block of the Lower Yangtze Region, Eastern China. Nine sedimentary basins are identified in which the Pukou Formation of the Upper Cretaceous has been deposited. From south to north, the nine sedimentary basins are named: Wangjing, Qianshan, Wuwei, Nanxuan, Changzhou, Jurong, Nanjing, Quanjiao and Subei basins. They form a wedge-shape fragment (the Yangzhou Block) occupying an area of 100,000 km² in the Lower Yangtze Region. The two side boundaries of the Yangzhou Block are the strike-slip Tanlu Fault and the strike-slip Quangjiao–Xiangshui Fault on the northwest and the strike-slip Qingyang–Nantong Fault on the southeast. The wide end of the wedge faces the Southern Yellow Sea in the northeast and the narrow end contacts the Dabie Block in the southwest.During the Early Mesozoic, collision between the Yangtze Block and the North China Block resulted in the formation of the Qinling–Dabie Orogenic Belt and caused the Lower Yangtze Region to become a foreland basin with many strike-slip faults. During the Late Mesozoic, wide spread extension in Eastern China and shortening in Qinling/Dabie Shan and in the Huaying Shan region resulted following establishment of an Andean-type arc margin to the east of the Southern Yellow Sea area, when ‘Greater Japan’ collided with Asia. Consequently, the wedge-shaped Yangzhou Block escaped tectonically toward the northeast and formed distinctive geological features in nine sedimentary basins during Pukou time in the Late Cretaceous. These geological features are reflected in basin spatial distributions, basin geometries, sedimentary facies, sediment thicknesses, sedimentary environments, and the petrology of fanglomerates and sandstones. These basins are part of a large population of arc-crestal rifts formed on top of that Andean arc.The proposed tectonic escape model could be useful in petroleum exploration and mining in the region.     

West Pacific-type convergent boundaries and their role in the formation of the Central Asian Fold Belt

The type of convergent boundaries forming in the area of mantle plumes is considered. These convergent boundaries (West Pacific type) are characteristic of the western margin of the Pacific. West Pacific-type boundaries are a regular succession of structures from ocean to continent: island arcs, marginal basins, rift basins, and associated OIB-type volcanics at the continental edge. The convergence zones are up to a thousand kilometers wide.Studies of the history of the part of the Central Asian Fold Belt forming the folded periphery of the Siberian continent have shown that the continent drifted above the African plume or corresponding low-velocity mantle province for most of the Phanerozoic (up to the Early Mesozoic inclusive). This fact determined the West Pacific type of convergent boundaries for the accretionary structures of the Central Asian Fold Belt. The drift of Siberia from African to Pacific province in the Late Cenozoic determined the structure and development of the convergent boundary in the western Pacific, including extensive intraplate magmatism in continental Asia in the Late Mesozoic and Cenozoic.     

福建省金矿床成矿时代特点

福建是我国东南沿违法乱纪半区金矿产区之一，既是古特提期成矿域东缘的组成部分，又受中国东部中生代环太平洋成矿带成矿作用的强烈叠加，且与基底变质岩（前寒武系）关系密切。福建金矿床总体具有成矿物质主要来源于基底变质岩，后期岩浆液改造富集，与不同层次的剪切带有关，受区域构造控制等特点。其成矿时代特征则具有“一老一新两期（元古宙和中生代且以中生代为主）成矿”和“成矿物质来源老，矿床定位时代新”等特点，金矿床成矿时代普遍为中生代或与中生代岩浆活动关系密切。此外，福建与华南地区的金矿床在地质特征上具有比较多的一致性，而与华北和西北地区在成矿时代特点上存在一定的差异性。     

Review of seafloor spreading around Australia. I. synthesis of the patterns of spreading

The existing data on Late Mesozoic and Cenozoic seafloor spreading isochrons (reviewed in the companion paper by Veevers & Li) and fracture zone trends provide the basis for 12 reconstructions of the seafloor around Australia that spread during the dispersal of Argo Land, India, Antarctica, Lord Howe Rise/New Zealand and the Papuan Peninsula. The major changes of plate geometry in the Jurassic, Early Cretaceous, mid‐Cretaceous, early Paleocene and early Eocene reflect global events. The pattern of spreading around Australia was determined by two long‐standing (earlier Phanerozoic) factors that operated in a counter‐clockwise direction: (1) penetration from the northwest by the Tethyan divergent ridge; and (2) rotation from the northeast of the Pacific convergent arc and back‐arc. The only new feature of the modern pattern is the deep penetration by the Indian Ocean ridge into eastern Gondwanaland to fragment it into continents in contrast with the pattern up to 160 Ma ago of breaking off micro‐continents.     

Southern African Phanerozoic marine invertebrates: Biogeography,pal˦oecology,climatology and comments on adjacent regions

The Palaeozoic marine invertebrate fossil record in southern Africa is characterised by extensive data for the Early and Middle Devonian but extremely limited or absent for other Palaeozoic Periods. The Mesozoic Era is lacking in marine invertebrate fossils for the Triassic, Late Jurassic, and Cretaceous. For the Cenozoic Era there is limited marine megafossil information. Overall, in benthic, cool waters, Palaeozoic, marine megafossils from southern Africa appear to represent relatively low diversity communities, when compared to ecologically comparable warm water environments elsewhere. However, the marine benthic Cretaceous and Cenozoic faunas of southwestern Africa are typically diverse warm water types, until the later Miocene when cool waters again prevailed. The Benguela Current clearly influenced lower diversity faunas.Climatically, it can be inferred from the marine megabenthic pal˦ontological evidence, thatwarm conditions were present from Early Cambrian until mid-Ordovician times, followed by a much cooler climate that persisted well into the Middle Devonian. The Late Palaeozoic evidence thus indicates cool to cold conditions. In contrast, the Late Permian fossils are consistent with warmer conditions, continuing through Late Jurassic and Cretaceous times along the East African and West African coasts, until the Late Miocene.Within the Gondwanan framework, a Central African region can be envisaged that was subject to non-marine conditions during the entire Phanerozoic Eon. Peripheral to this central African region were marine environments of various ages. The geological history of these peripheral regions was fairly unique. Some features in southern Africa are similar of those found in the Paraná Basin and the Falkland Islands.Most of North Africa from central Senegal to Libya contains a Phanerozoic marine cover extending from the Early Cambrian through to the Carboniferous, characterised by warm water faunas, except for the Ordovician which yields cool-cold water faunas.The Palaeozoic of Arabia, which was an integral part of Africa until the Miocene, has yieldedwarm water fossils.