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1.
The Arthur Lineament of northwestern Tasmania is a Cambrian (510 ± 10 Ma) high‐strain metamorphic belt. In the south it is composed of metasedimentary and mafic meta‐igneous lithologies of the ‘eastern’ Ahrberg Group, Bowry Formation and a high‐strain part of the Oonah Formation. Regionally, the lineament separates the Rocky Cape Group correlates and ‘western’ Ahrberg Group to its west from the relatively low‐strain parts of the Oonah Formation, and the correlated Burnie Formation, to its east. Early folding and thrusting caused emplacement of the allochthonous Bowry Formation, which is interpreted to occur as a fault‐bound slice, towards the eastern margin of the parautochthonous ‘eastern’ Ahrberg Group metasediments. The early stages of formation of the Arthur Lineament involved two folding events. The first deformation (CaD1) produced a schistose axial‐planar fabric and isoclinal folds synchronous with thrusting. The second deformation (CaD2) produced a coarser schistosity and tight to isoclinal folds. South‐plunging, north‐south stretching lineations, top to the south shear sense indicators, and south‐verging, downward‐facing folds in the Arthur Lineament suggest south‐directed transport. CaF1 and CaF2 were rotated to a north‐south trend in zones of high strain during the CaD2 event. CaD3, later in the Cambrian, folded the earlier foliations in the Arthur Lineament and produced west‐dipping steep thrusts, creating the linear expression of the structure. 相似文献
2.
A. R. Reed 《Australian Journal of Earth Sciences》2013,60(6):785-796
Recumbent folding in eastern Tasmania affected turbidites containing Lower to Middle Ordovician (Bendigonian Be1 to Darriwilian Da3) fossils, but not stratigraphically overlying turbidites containing Silurian (Ludlow) graptolites, and is of a timing consistent with Ordovician to Silurian Benambran orogenesis on the Australian mainland. Two subsequent phases of upright folding post‐date deposition of turbidites containing Devonian plant fossils but pre‐date intrusion of Middle Devonian granitoids, and are of Tabberabberan age. A closely spaced disjunctive cleavage (S2), associated with the first phase of Tabberabberan folding, everywhere cuts a slaty cleavage (S1) associated with the earlier formed recumbent folds. However, refolding associated with development of S2 is not always clear in outcrop and it is proposed that coincident tectonic vergence between the two events has resulted in reactivation of recumbent D1 structures during the D2 event. The transition to rocks not affected by recumbent folding coincides with a marked change in sedimentology from shale‐ to sand‐dominated successions. This contact does not outcrop but, from seismic data, appears to dip moderately to the east, and can only be explained as an unconformity. The current grouping of all pre‐Middle Devonian turbidites in eastern Tasmania into the one Mathinna Group is misleading in that the turbidite sequence can be subdivided into two distinct sedimentary packages separated by an orogenic event. It is proposed that the Mathinna Group be given supergroup status and existing formations placed into two new groups: an older Early to Middle Ordovician Tippogoree Group and a younger Silurian to Devonian Panama Group. 相似文献
3.
Geochemical Features, Age, and Tectonic Significance of the Kekekete Mafic-ultramafic Rocks, East Kunlun Orogen, China 总被引：3，自引：0，他引：3
LI Ruibao PEI Xianzhi LI Zuochen SUN Yu FENG Jianyong PEI Lei CHEN Guochao LIU Chengjun CHEN Youxin 《《地质学报》英文版》2013,87(5):1319-1333
The Kekekete mafic-ultramafic rocks are exposed in the Kekesha-Kekekete-Dawate area,which are in the eastern part of the East Kunlun Orogenic Belt.It outcrops as tectonic slices intruding tectonically in the Paleoproterozoic Baishahe Group and the Paleozoic Nachitai Group.The Kekekete mafic and ultramafic rocks is located near the central fault in East Kunlun and lithologically mainly consists of serpentinite,augite peridotite,and gabbro.The LA-ICP-MS zircon U-Pb age of the gabbro is 501±7 Ma,indicating that Kekekete mafic-ultramafic rocks formed in the Middle Cambrian.This rock assemblage is relatively poor in SiO2 and(Na2 O+K2 O) but rich in MgO and SFeO.The chondrite-normalized REE patterns of the gabbro dip slightly to the right;the primitive mantle and MORBnormalized spidergrams of trace elements show enrichment of large-ion lithophile elements(Cs,Rb,Ba,etc.) and no differentiation of high field strength elements.The general dominance of E-MORB features and the geochemical characteristics of OIB suggest that the Kekekete mafic-ultramafic rocks formed in an initial oceanic basin with slightly enriched mantle being featured by varying degrees of mixing of N-MORB depleted mantle and a similar-OIB-type source.From a comprehensive study of the previous data,the author believes that the tectonic history of the East Kunlun region was controlled by a geodynamic system of rifting and extension in the late stages of the Neoproterozoic to early stages of the Early Paleozoic and this formed the paleo-oceanic basin or rift system now represented by the ophiolites along the central fault in East Kunlun,the Kekekete mafic-ultramafic rocks and Delisitan ophiolite. 相似文献
4.
Emyr Williams 《Tectonophysics》1978,48(3-4)
In western Tasmania Eocambrian and Cambrian rock sequences accumulated in narrow troughs between and within Precambrian regions which became geanticlines. The largest trough is meridional and is flanked by the Tyennan Geanticline to the east and the Rocky Cape Geanticline to the west. Within this trough ultramafic and mafic igneous masses, some of which are dismembered ophiolites, occur below a structurally conformable but erosional surface. This surface is at the base of an early-Middle Cambrian turbidite sequence, which grades upward into a probable correlate of the Owen Conglomerate that ranges into the Ordovician. Fault-bounded areas of Rocky Cape strata occur at the eastern boundary of the sedimentary trough deposits. A considerable pile of mineralized calcalkalic volcanic material, in which granite was emplaced, accumulated between the sedimentary trough deposits and the Tyennan Geanticline. Movements along Cambrian faults near and parallel to the margin of the Tyennan Geanticline caused angular unconformities. Above the unconformities occur volcaniclastic sequences that pass conformably upward into shallow marine and terrestrial Owen Conglomerate, derived from the Tyennan Geanticline.The transgressive Owen Conglomerate and its correlates are followed conformably by shallow marine limestone, of Early to Late Ordovician age. These limestone deposits covered much of western Tasmania and are succeeded conformably by Silurian to Early Devonian beds of shallow-marine quartz sandstone and mudstone.Pre-Middle Devonian rocks of western Tasmania extend to the Tamar Tertiary trough. In the northeast of Tasmania, immediately to the east of the Tamar trough, are sequences of interbedded mudstone and turbidite quartz-wacke of the Mathinna Beds, ranging in age from Early Ordovician to Early Devonian.The Cambrian to Early Devonian rocks of Tasmania are extensively deformed and show flattened parallel folds. In western Tasmania the folds are dated as late-Early to early-Middle Devonian because fragments of the deformed rocks occur in undisturbed Middle Devonian terrestrial cavern fillings. Folds of the northeastern Tasmania Mathinna Beds are probably of the same age. This widespread Devonian deformation is correlated with the Tabberabberan Orogeny of eastern Australia.In western Tasmania the geanticlines of Cambrian times behaved as relatively competent blocks during the Devonian folding, which is of two main phases. In the earlier phase the competent behaviour of the Tyennan Block determined the fold patterns. In the north the dominantly later folds resulted from movement from the northeast. During this later Devonian phase the Tyennan Block yielded in a northwesterly trending narrow zone of folding.In northeast Tasmania the Mathinna Beds exhibit folds which indicate a tectonic transportation opposite in direction to that which resulted in the folds of similar age in western Tasmania.Granitic rocks, dated 375-335 m.y., were emplaced within the folded rocks of Tasmania with usually sharp, discordant contacts. Foliations in the batholiths of northeast Tasmania suggest post-intrusion deformations involving east—west flattening. The late deformations may be related to lateral movements along a fracture zone which brought the Mathinna Beds of northeast Tasmania into juxtaposition with the rocks of contrasting stratigraphical and structural characteristics of western Tasmania.Flat-lying Late Carboniferous and younger deposits rest unconformably on the older rocks. 相似文献
5.
J. A. Mulder R. F. Berry J. A. Halpin S. Meffre J. L. Everard 《Australian Journal of Earth Sciences》2018,65(3):391-407
The Proterozoic Oonah Formation comprises a thick sequence of turbidites and mafic rocks that is widely exposed in western and northern Tasmania. The regional significance of the Oonah Formation is poorly understood as its contacts are faulted and estimates of its depositional age range from 1450 Ma to 700 Ma. Here we refine the depositional age of the Oonah Formation and clarify its relationship to other Proterozoic sequences in Tasmania. Magmatic apatite from the syn-sedimentary Cooee Dolerite has a 207Pb-corrected 238U/206Pb age of 733 ± 9 Ma that provides a robust estimate of the depositional age of the Oonah Formation. The Oonah Formation contains abundant 750 Ma detrital monazite and has detrital zircon age populations at 1800–1700 Ma, 1590 Ma, and 1450 Ma. The new age and provenance data support the interpretation that the Oonah Formation is a lateral equivalent of the base of the Togari Group and correlatives in Tasmania. We demonstrate that the stratigraphy and provenance of Neoproterozoic strata in Tasmania differ from time-equivalent sequences in Adelaide Rift Complex but are similar to the Pahrump Group (Death Valley, California) and the Cobham Formation (Transantarctic Mountains), which supports a southwest Laurentia—Tasmania—East Antarctica connection within supercontinent Rodinia. 相似文献
6.
Crustal architecture in formerly contiguous basement terranes in SE Australia, Tasmania and northern Victoria Land is a legacy of late Neoproterozoic–Cambrian subduction-related processes, culminating in formation of the Delamerian–Ross orogen. Structures of Delamerian–Ross age were subsequently reactivated during late Mesozoic–Cenozoic Gondwana breakup, strongly influencing the geometry of continental rifting and providing clues about the origins and configuration of the pre-existing basement structures. An ocean–continent transform boundary developed off western Tasmania follows the trace of an older Paleozoic strike-slip structure (Avoca–Sorell fault system) optimally oriented for reactivation during the final separation of Australia from Antarctica. This boundary cuts across rocks preserving an earlier record of arc–continent collision during the course of which continental crust was subducted to mantle depths and Cambrian mafic–ultramafic island arc rocks were thrust westwards over late Neoproterozoic–Cambrian passive margin sequences. Collision was accompanied by development of a foreland basin into which 520–600 Ma arc-derived detrital zircons were shed. Following a reversal in subduction polarity, and change to transcurrent motion along the Gondwana margin, Tasmania migrated northward along the proto-Avoca fault system before entering a subduction zone located along the Heathcote–Governor fault system, precipitating a second collision, south-vergent thrusting, and tectonic reworking of the already accreted Cambrian arc–forearc assemblages and underlying passive margin sequences. 相似文献
7.
前寒武纪盆地演化及造山作用一直是造山带研究中的热点和难点,通过对华北克拉通东部陆块胶-辽-吉构造带中辽东半岛河栏镇火山-沉积岩进行深入的野外及室内研究,反演该地区古元古代大地构造演化过程.通过对辽河群里尔峪组火山岩、高家峪组钙质泥岩以及大石桥组碳酸盐岩野外的详细构造解析,识别出各类岩石单元中发育同沉积伸展构造（D1-0）,包括同沉积不对称褶皱、层间平卧褶皱和滑脱面理及线理,指示辽吉弧后盆地早期伸展张裂过程.通过对河栏镇蒲石河地区基性侵入岩及喷出枕状熔岩进行详细的野外构造填图及解析,提出伴随基性枕状熔岩的喷发,辽吉弧后盆地张裂到最大程度.此外,在各组相关岩石中观察到大量逆冲推覆构造及不对称断展褶皱,构造归为D1-1或者D1-2,指示辽吉弧后盆地受挤压应力影响发生收缩.锆石年代学研究指示高家峪组沉积物物源主要来自于~2.5 Ga基底,少量来自古元古代（2 172 Ma）火山弧.综合区域内已有岩石地球化学及年代学资料,研究表明辽吉弧后盆地的拉张及闭合过程伴随着古元古代增生造山作用,并暗示板块构造在古元古代已经开启. 相似文献
8.
Maxwell R. Banks 《Australian Journal of Earth Sciences》2013,60(2):189-215
Summary Late in the Carboniferous Period or early in the Permian ice covered much of Tasmania (Fig. 30b). The sub‐Permian surface had a relief of several thousand feet with particularly low areas near Wynyard and Point Hibbs and high areas near Cradle Mountain, Devonport, Deloraine, Wylds Crag and Ida Bay and a peninsula in eastern Tasmania (Fig. 30a). The glaciers from an ice centre north‐west of Zeehan diverged about a higher area near Cradle Mountain. One tongue occupied a deep valley near Wynyard and a lobe fanned out south of the high area to occupy parts of northern and central Tasmania and to override some parts of the east coast peninsula. West of Maydena the ice scoured shell beds and dumped the shell fragments in the till on the Styx Range. Thus the base of the ice may well have been below sea‐level. Carey and Ahmad (1961) suggested that the Wynyard Tillite was deposited below a “wet‐base” glacier. David (1908, p. 278) suggested deposition from “land ice in the form of a piedmont or of an ice‐sheet” but that near Wynyard the ice came down very close to, if not actually to, sea‐level. The extent of the glaciation and the distribution of erratics of western Tasmanian origin in eastern Tasmania make it seem likely that either a piedmont glacier or an ice‐sheet rather than mountain glaciation was involved. Following retreat of the glaciers the sea covered the till, probably to a considerable depth, eustatic rise of sea‐level being much more rapid than isostatic readjustment. The Quamby Group is underlain by or passes laterally into thin conglomerates and sandstones in a number of places, but most of the group appears to be of deep water, partially barred basin origin. Marine oil shales accumulated close to islands. Shallowing of the sea during deposition of the upper part of the Quamby Group seems to be indicated by the fauna and increasing sandiness in marginal areas. Instability in the source areas is shown by the presence of turbidity current deposits in the higher parts of the group. The Golden Valley Group, of Upper Sakmarian and perhaps Lower Artinskian age, was deposited in a shallower sea than the Quamby Group but the deposits are more extensive along the east coast peninsula and on the flanks of the Cradle Mountain island. This anomaly may be explained if the rate of deposition exceeded the rate of rise of sea‐level. The sediments of the Golden Valley Group became finer‐grained upwards in most parts of Tasmania probably indicating reduction in relief of the source area. Some instability is indicated by turbidity current deposits. Uplift of source areas in north‐western Tasmania early in Artinskian time resulted in the spreading of sand over the shallow silts of the Golden Valley Group onto the east coast peninsula and over the Cradle Mountain area. The sand formed a wide coastal plain containing lakes and swamps and the sea was restricted to a small gulf in southern Tasmania during the deposition of the lower part of the Mersey Group. During deposition of this group the sea rose once to form a long, narrow gulf extending as far north as Port Sorell and then retreated. This inundation resulted in the development of two cyclothems in many parts of Tasmania. A little later in Lower Artinskian time the sea rose and covered most of Tasmania except perhaps the far north‐west. This wide transgression probably resulted from down‐warping as an eustatic rise in sea‐level would be expected to produce thickest deposition over the old gulf in southern Tasmania and along the axis of Mersey Group inundation but the zone of thickest Cascades Group crosses these at a high angle. During deposition of the Cascades Group marine life became very abundant in the shallow sea over which a few icebergs floated. During the Artinskian tectonic instability increased as shown by the increasing number of turbidites in the upper part of the Grange Mudstone and the lower part of the Malbina Formation. The sea became less extensive and the source areas in north‐western and north‐eastern Tasmania were uplifted. The zone of thickest deposition of the Malbina Formation trended north‐north‐westerly. The rapid succession of turbidity currents killed the benthonic fauna and it was only during deposition of the upper part of the formation possibly in Lower Kungurian time that life became abundant again in the Hobart area. The sea spread a little over the east coast peninsula and further instability is recorded in the Risdon Sandstone. The resulting turbidity currents killed the benthonic fauna and it never became properly established again in any part of Tasmania during the Permian. A wide shallow sea covered much of Tasmania and was bordered by low source areas during deposition of the Ferntree Group. The axis of greatest thickness had an almost meridional trend and lay west of that of the Malbina Formation. Late in the Permian, probably in the Tartarian, rejuvenation of the source areas, particularly in western Tasmania, and withdrawal of the sea, resulted in deposition of sands and carbonaceous silts of the Cygnet Coal Measures. The zone of greatest thickness was almost parallel to but west of that of the Ferntree Group. The thickness of the Permian System and the sheet‐like character of many of the members and formations suggest shelf rather than geosynclinal deposition. The average rate of deposition was of the order of 1 ft. in ten thousand years (about 0–003 mm./annum). However, the sediments differ markedly from those on stable shelves in that many of them are poorly‐sorted. Some of the poor sorting may be attributed to deposition from drifting icebergs but some is due to tectonic instability. Uplift and downwarping and movement of zones of maximum thickness have been deduced above and it is probable that the tectonic instability started as early as Lower Artinskian and it may have started during Sakmarian (upper part of Quamby Group). Maximum instability seems to have occurred in Middle or Upper Artinskian time (Malbina Formation) and it is probably significant that this was a time of considerable orogenic movement in New South Wales (part of the Hunter‐Bowen Orogeny, Osborne, 1950). Progressive westward movement of zones of maximum thickness of units in Upper Permian time seems to have occurred and this again is reminiscent of the situation at the time in New South Wales (Voisey, 1959, p. 201) but seems to have started later. Uplift and development of a major synclinal structure with a trend approximately north‐north‐westerly occurred late in Permian time. 相似文献
9.
秦岭造山带主要大地构造单元的新划分 总被引：48，自引：6，他引：42
根据近年来的地层、沉积、岩浆-火山和构造变形及岩石地球化学等方面研究新进展,结合前人的成果,按照大地构造相单元划分原则,将秦岭造山带分为13个主要构造单元: ①华北南缘陆坡带,包括第一层序的青白口系大庄组、震旦系罗圈组和寒武系,与之对应的豫西栾川群;第二层序的奥陶纪陶湾群;②北秦岭弧后杂岩带,以宽坪群和部分二郎坪群中的基性火山岩与碳酸盐岩的构造块体与变质的古生代深海碎屑岩混杂为特征;③秦岭岛弧杂岩带,由丹凤群不同的古洋隆块体、富水幔源岛弧基性岩浆杂岩、云架山群、斜峪关群和草滩沟群的岛弧钙碱性岩浆岩和火山岩及深海沉积物及秦岭群弧基底杂岩等构成,时间跨度为奥陶纪-石炭纪;④秦岭弧前盆地系,泥盆系及其它晚古生代地层是其主要充填物,同沉积断裂控制了一系列的次级盆地;⑤秦岭增生混杂带,由泥、砂岩组成的基质和基性、超基性岩、火山岩、灰岩、硅质岩等岩块构成,最终形成于二叠纪末-三叠纪初;⑥南秦岭岛弧杂岩带,碧口群的基性-中酸性火山岩和岩浆岩组成,称碧口弧;由三花石群的中基性火山岩以及西乡群的中酸性火山岩共同构成,称西乡弧;由耀岭河群和郧西群中基性熔岩和中酸性火山岩组成,称安康弧;⑦南秦岭弧前盆地系,碧口弧前盆地充填物是以碎屑岩为主的横丹群和关家沟群;西乡弧前沉积主要由三花岩群包括王家坝组砂岩以及由泥岩、砂岩和中酸性火山岩变质而成的片岩、片麻岩和石英岩组成.安康弧前盆地具有明显的深海扇沉积特征梅子垭群和大贵坪组;⑧南秦岭弧后盆地系,包括后龙门山的茂县群和上古生界及三叠系,大巴山的洞河群和部分耀岭河群的火山岩;⑨南秦岭弧后陆坡带,只保留大巴山弧后陆缘,是高川-毛坝以南的下古生界;⑩南秦岭前陆褶冲带,包括龙门山北段、米仓山和大巴山前陆褶冲带.三带形成于印支-燕山期,但构造线不同,且在出现的时间上,由西到东由早到晚;(11)三叠纪残余海盆;(12)中-新生代走滑拉分和断陷盆地;(13)基底断块. 相似文献
10.
《地学前缘(英文版)》2022,13(3):101374
Mid-Devonian high-pressure (HP) and high-temperature (HT) metamorphism represents an enigmatic early phase in the evolution of the Variscan Orogeny. Within the Bohemian Massif this metamorphism is recorded mostly in allochthonous complexes with uncertain relationship to the major tectonic units. In this regard, the Mariánské Lázně Complex (MLC) is unique in its position at the base of its original upper plate (Teplá-Barrandian Zone). The MLC is composed of diverse, but predominantly mafic, magmatic-metamorphic rocks with late Ediacaran to mid-Devonian protolith ages. Mid-Devonian HP eclogite-facies metamorphism was swiftly followed by a HT granulite-facies overprint contemporaneous with the emplacement of magmatic rocks with apparent supra-subduction affinity. New Hf in zircon isotopic measurements combined with a review of whole-rock isotopic and geochemical data reveals that the magmatic protoliths of the MLC, as well as in the upper plate Teplá-Barrandian Zone, developed above a relatively unaltered Neoproterozoic lithospheric mantle. They remained coupled with this lithospheric mantle throughout a geological timeframe that encompasses separate Ediacaran and Cambrian age arc magmatism, protracted early Paleozoic rifting, and the earliest phases of the Variscan Orogeny. These results are presented in the context of reconstructing the original architecture of the Variscan terranes up to and including the mid-Devonian HP-HT event. 相似文献
11.
Eight dredges from the southern New South Wales continental slope sampled the offshore extension of the Lachlan Orogen. Two rock suites were recovered: (1) lower greenshist facies limestones, felsic volcanics, sandstones, mudstones and Moruya Suite granodiorite correlate with the onshore Silurian to mid-Devonian orogenic phase; and (2) a strongly deformed greenschist to lower amphibolite facies mafic volcanics, cherts, marbles, pelites and serpentinites correlate in part with the Cambro-Ordovician Wagonga Group of the Narooma Terrane. The mafic volcanic rocks have ocean island, tholeiitic and boninitic basalt affinities. The offshore distribution of ocean island basalt that correlates with medial Cambrian basalt breccias at Batemans Bay suggests a large seamount or seamount complex. The boninites, tholeiites and ultramafics could be part of a forearc-generated ophiolite. The Narooma Terrane basement is interpreted as the part of the bonititic arc postulated to have collided with Vandieland in late early Cambrian time. Mid-Cambrian rifting of the oceanward part of this arc remnant, generated the Albury–Bega Terrane oceanic basement exposed in the Howqua Valley in the west and Melville Point in the east. Overlying are upper–mid-Cambrian to lowermost Ordovician black shale and chert, Lower Ordovician to Gisbornian Adaminaby Group quartz turbidites and Gisbornian to lower Bolindian Bendoc Group black shales. Batemans Bay exposures are reinterpreted as a dismembered basin margin succession onlapping the west-facing attenuated flank of the Narooma Terrane. The Narooma Cambro-Ordovician cherts and mudstones were initially deposited outboard on the more elevated seamount flank elevated above the clastic-filled basin to the west. Benambran deformation commenced in latest Ordovician time uplifting the outer Narooma Terrane, shedding debris from the seamount and its flanks, culminating in allochthonous displacement of chert masses to the basin's eastern margin to Narooma, and emplacing them as a succession of thrust sheets. Contemporaneously, silt and mud of the Bogolo Formation, deposited from the west, were mixed with olistostomal basalt and chert debris from the east. Early Silurian westward tectonic transport of the Narooma Terrane ruptured the Albury-Bega basin floor at Batemans Bay, thrusting it and its sedimentary cover over its eastern margin as a series of thrusts each floored by melange (mapped Bogolo Formation), derived from the slope debris and its overpressured sedimentary cover. Offshore, the metamorphosed Benambran phase rocks are unconformably overlain by Tabberabberan cycle sediments and volcanics intruded by granodiorite. Our interpretation of the boundary between the Albury-Bega and Narooma terranes as a thrusted passive margin accumulation is incompatible with models of a Narooma Accretionary Complex formed by the subduction of the Paleopacific Plate. 相似文献
12.
宗务隆构造带位于柴北缘构造带与南祁连构造带之间,总体呈北西西向展布。构造带东段丰富的岩浆活动记录了该构造带晚古生代—中生代期间的裂解和闭合过程,而西段岩浆活动的记录较为稀少,对于其东、西段是否具有相同的构造演化尚不清晰。通过分析构造带西段三叠系隆务河组碎屑岩的地球化学特征、碎屑锆石U-Pb年龄及Hf同位素组成,认为隆务河组的碎屑沉积物的源区古风化程度轻微,不具备沉积再循环的特征,原岩主要为长英质岩石,南祁连新元古代花岗质片麻岩和早古生代大陆弧型花岗岩为隆务河组碎屑岩的主要物源;碎屑岩可能沉积于早中三叠世挠曲型盆地中;锆石U-Pb年龄分析表明宗务隆构造带东西段构造演化具有不同的历程,东段发育有限洋盆,而西段并未出现,转换地带可能位于生格至罗根郭勒之间。 相似文献
13.
E. C. Leitch C. L. Fergusson R. A. Henderson V. J. Morand 《Australian Journal of Earth Sciences》2013,60(6):571-579
Ophiolitic and metamorphic rocks of the eastern part of the New England Fold Belt in the Shoalwater Bay region and the Percy Isles are grouped in the Marlborough and Shoalwater terranes, respectively. Marlborough terrane units occur on South Island (Percy Isles) and comprise the Northumberland Serpentinite, antigorite serpentinite with rodingite and more silicic dykes and mafic inclusions, the Chase Point Metabasalt, some 800+ metres of pillow lava, and the intervening South Island Shear Zone containing fault‐bounded slices of mafic and ultramafic igneous rocks, schist, and volcaniclastic sedimentary rocks, and zones of mélange. The Shoalwater terrane, an ancient subduction complex, consists of the Shoalwater Formation greenschist facies metamorphosed quartz sandstone and mudstone on North East Island and on the mainland at Arthur Point, the Townshend Formation, amphibolite‐grade quartzite, schist and metabasalt on Townshend Island, and the Broome Head Metamorphics on the western side of Shoalwater Bay, upper amphibolite facies quartz‐rich gneiss. With the exception of a sliver emplaced onto the western Yarrol terrane, possibly by gravity sliding, Shoalwater terrane rocks show the effects of Late Permian polyphase deformation. The Shacks Mylonite Zone along the northwest edge of the Broome Head Metamorphics marks a zone of oblique thrusting and is part of the major Stanage Fault Zone. The latter is a northeast‐striking oblique‐slip dextral tear fault active during Late Permian west‐directed thrusting that emplaced large ultramafic sheets farther south. Marlborough terrane rocks were emplaced along the Stanage Fault Zone, probably from the arc basement on which rocks of the Yarrol terrane were deposited. Structural trends and the distribution of rock units in the Shoalwater Bay‐Percy Isles region are oblique to the overall structural trend of the northern New England Fold Belt, probably due to the presence of a promontory in the convergent margin active in this region in Devonian and Carboniferous time. 相似文献
14.
This study presents new data on the deformational and metamorphic history of previously unstudied Cambrian high-pressure metamorphic rocks exposed on the remote south coast of Tasmania. The Red Point Metamorphic Complex consists of two blocks of high-pressure, medium-grade metamorphic rocks including pelitic schist and minor garnet-bearing amphibolite, which are faulted against a sequence of low-grade phyllite and quartzite. The Red Point Metamorphic Complex records five phases of deformation, all of which except the first are expressed at a mesoscopic scale in both the medium- and low-grade rocks. Peak metamorphic conditions in the high-pressure epidote–amphibolite facies is recorded by medium-grade schist and amphibolite and was synchronous with the second major deformation event, which produced a pervasive schistosity and mesoscale isoclinal folds. The juxtaposition of the low- and medium-grade rocks is interpreted to have first occurred prior to the development of upright, opening folding associated with the third deformation. However, the present contacts between the two contrasting metamorphic sequences formed during widespread faulting and ductile-shear zone development associated with the fourth and fifth deformation events. The new data from the Red Point Metamorphic Complex provide insights into the structural and metamorphic history experienced by the medium-grade rocks of Tasmania during the Cambrian Tyennan Orogeny. This study demonstrates that Cambrian medium-grade metamorphic rocks are more widespread throughout Tasmania than previously realised, which represents an important step towards understanding the large-scale architecture of the Tyennan Orogen. 相似文献
15.
在新疆叶城县的西昆仑麻扎构造混杂岩带内,发育一套含煤砂砾岩地层,原陕西省地质调查院在1∶25万区域地质调查中,将其划分为3个地层填图单元,即三叠系(T,未分)、三叠系赛力亚克达坂群(TS)和早—中侏罗世叶尔羌群(J1-2Y)。这些碎屑岩主体是造山作用形成的山间磨拉石沉积,但各地层单元之间多为断层接触,顶底不全,岩石地层之间的新老关系和形成时代也不清楚。通过对该套碎屑岩的详细剖面测制和分析,依据其岩石组合特征、生物地层特征对比,将该套含煤砂砾岩重新厘定为早—中侏罗世叶尔羌群(J1-2Y),并自下而上再划分为:莎里塔什组(J1s^)、杨叶组(J2y)、塔尔尕组(J2t)。它们主要是一套河湖相沉积的地层,是对西昆仑构造混杂岩带在早—中侏罗世隆起造山的沉积响应。 相似文献
16.
R. F. Berry K. Goemann J. Thompson S. Meffre R. Bottrill 《Australian Journal of Earth Sciences》2019,66(2):227-246
The Ordovician Turquoise Bluff Slate in northeastern Tasmania is a 2?km-thick sequence of deep-marine siliceous black slates. It is dominated by meta-siltstones with bimodal grainsize distributions typical of turbidite TE-1 and TE-2 facies. The slates have high SiO2 indicating they are hemipelagites. The high Ba and V indicate they were deposited in an anoxic environment associated with high oceanic productivity. All these features are common in muddy turbidites. U–Th–Pb dating of detrital monazite and authigenic xenotime in the slates supports previous evidence that the dominant cleavage, in this unit, formed during the Benambran Orogeny. The whole-rock composition of the slates is similar to black slates in the Adaminaby Group, NSW. A review of Paleozoic whole-rock compositions from the Lachlan Orogen confirms they all have trace element contents similar to average Australian shale. However, there are subtle differences in composition. The Turquoise Bluff Slate and other Mathinna Supergroup rocks from the Eastern Tasmania Terrane have higher average Cr content than similar age turbidites from Victoria and NSW. This probably reflects a small contribution from Tasmania Cambrian ultramafic rocks in the provenance. If this were correct, northeastern Tasmania was closer to western Tasmania in the Paleozoic than other provinces of the Lachlan Orogen, southeastern Australia. Other subtle features of the whole-rock composition of Paleozoic sedimentary rocks from the Lachlan Orogen indicate it may be possible to recognise provincial variations in composition that will provide new constraints on tectonic models of southeastern Australia. 相似文献
17.
The Woodlands Formation (uppermost Pretoria Group) of eastern Botswana overlies thick quartzites of the Sengoma Formation (Magaliesberg Formation) and comprises a lower unit of interbedded mudrocks and fine-grained recrystallised quartzitic sandstones, succeeded by chaotic and very coarse-grained inferred slump deposits. Within the adjacent western region of South Africa, interbedded mudrocks and quartzitic sandstones stratigraphically overlying the Magaliesberg Formation are now assigned to the lower Woodlands Formation. Within the entire region, interference folding produced by northeast-southwest (F1 and F3) and northwest-southeast (F2) compression, and concomitant faulting characterised inversion of the Pretoria Group basin. This deformation is of pre-Bushveld age and affected all units in the Pretoria Group, including the uppermost Silverton, Magaliesberg and Woodlands Formations, and intrusive Marico Hypabyssal Suite (pre-Bushveld) mafic sills. The Nietverdiend lobe of the Bushveld Complex, intrusive into this succession, was not similarly deformed. Movement along the major Mannyelanong Fault in the northwest of the study area post-dated Transvaal Basin inversion, after which the “upper Woodlands” chaotic slump deposits were formed. The latter must thus belong to a younger stratigraphical unit and is possibly analogous to apparently syntectonic sedimentary rocks (Otse Group) in the Otse Basin of eastern Botswana. 相似文献
18.
林芝地区雅鲁藏布江大峡谷西侧的尼洋河、雅鲁藏布江河谷地带,广泛出露有属冈底斯岩浆弧基底岩系的林芝岩群。笔者等在2001—2004年进行1∶25万林芝县幅区域地质调查中,于雅鲁藏布江东岸的里龙及西岸扎西绕登一带,在林芝岩群下部中高级变质基性岩中新发现呈透镜状、饼状、瘤状、长条状、豆荚状等零星分布的麻粒岩。初步研究,化学成分具有富MgO,高CaO,低TiO2、K2O,Al2O3/TiO2比值接近20,与世界上典型玄武质科马提岩特征相似;稀土总量较底,类似于中—基性火山岩;原岩可能为一套富镁的超镁铁—镁铁质火山岩系。时代属古元古代。 相似文献
19.
N. Yu. Bragin 《Stratigraphy and Geological Correlation》2010,18(2):118-132
Data on the studied radiolarians from cherty rocks are used to distinguish stratigraphic subdivisions of diverse volcanogenic
rocks in the Dhiarizos Group of the allochthonous Mamonia Complex, in Southwest Cyprus. The results obtained confirm the Triassic-Early
Cretaceous age of a basalt-chert-carbonate succession corresponding to the Phasoula Formation and first define the Early Jurassic
age of basalt-diabase breccias in the Loutra tis Aphroditis Formation. The results represent new basis for deciphering the
Mesozoic geological history of Cyprus and East Mediterranean. 相似文献
20.
在保山地块西缘泸水-潞西构造带内, 出露一套构造混杂岩.主体为强变形的震旦系-古生界蒲满哨群、公养河群浅变质碎屑岩夹碳酸盐岩及火山岩等复理石浊积岩系等构成, 另有硅质岩、杂砂岩、灰岩、砾岩、玄武岩及花岗岩等弱变形的构造块体.岩石时代从震旦纪至古生代, 跨度大, 高度混杂, 并有从东向西变新的逐势, 表现为后退式增生.构造样式早期为同斜倒转冲断作用的叠瓦构造, 后期表现为近N-S向剪切.玄武安山岩、流纹岩类具弧火山岩特征, 而玄武岩类则为板内火山岩, 2种火山岩分别对应岛弧与弧后拉张洋盆产物.寒武纪、奥陶纪侵位的花岗岩也分为东西2个带, 西晚东早, 代表了保山陆块西缘岩浆弧的一部分.这样就记录了洋壳俯冲消亡、增生楔形成过程的沉积、火山-岩浆、变质和构造变形的地质事件群, 也记录了保山地块西缘早古生代增生造山形成过程的地质事件, 并证明了泸水-潞西构造带在震旦纪-古生代存在一洋盆. 相似文献