Geology and petroleum potential of the Fairway Basin in the Tasman Sea     

N. F. Exon  Y. Lafoy  P. J. Hill  G. R. Dickens  I. Pecher 《Australian Journal of Earth Sciences》2013,60(5):629-645

The Fairway Basin is a large, generally north – south-trending, sediment-filled structure in water 1500 – 3000 m deep, on the eastern slope of the Lord Howe Rise in the Tasman Sea, and is partly within Australian jurisdiction. It was poorly known until a few years ago, when seismic profiling and piston coring cruises were carried out. The basin, about 1100 km long and 120 – 200 km wide, can be divided into three segments—north, central and south—that trend northwest, north and north-northwest, respectively. All three segments probably formed by thinning of continental crust during breakup of Lord Howe Rise and surrounding aseismic continental ridges in the Late Cretaceous and Paleocene. Normal faulting, large inputs of terrigenous sediment and subsidence to bathyal marine depths occurred during that time. A period of compression, perhaps related to overthrusting on New Caledonia, occurred in the Eocene, leading to uplift (and in parts, erosion) of northern Lord Howe Rise, and reversal of faulting in the basin. By the Oligocene, the area was again in bathyal depths, and pelagic ooze and some turbidites accumulated. The basinal sequence is generally 2000 – 4000 m thick, with 1200 – 3200 m of Cretaceous to Eocene sediment concentrated in depocentres, capped by 500 – 800 m of Oligocene and younger sediment. In the depocentres, numerous sedimentary diapirs pierce sedimentary sequences. The sedimentary diapirs appear to be fed by Cretaceous muds deposited during rifting. Often, these diapirs are overlain by faults extending to the seafloor, and hummocky bathymetry is possibly caused by fluid escape. The overall geology suggests that the Fairway Basin may be a large frontier hydrocarbon province. Seismic profiles display a bottom-simulating reflector above many depocentres, 500 – 700 m below the seafloor. The bottom-simulating reflector has positive polarity, which could result from a diagenetic phase transformation, a thin gas hydrate layer with a sharp top, or from the sharp base of a gas layer (probably beneath gas hydrates). Standard piston cores taken above diapirs and apparent fluid-escape features have recovered little gas. Other than drilling, the next steps in assessing petroleum potential are to clearly document fluid-escape structures, and to sample any fluids emitted for hydrocarbons.  相似文献   

Analyse quantitative du rifting et de la relaxation thermique de la partie occidentale de la marge transformante nord-africaine: le Rif externe (Maroc)     

Philippe Favre 《Geodinamica Acta》2013,26(2):59-81

Résumén

Un résumé de la cinématique du Rif externe central et occidental, de la période de rifting aux événements tectoniques récents, est proposé. L’évolution du Rif externe est abordée sur le plan quantitatif par le biais des principaux mécanismes physiques qui ont pu affecter cette partie de la marge nord-africaine durant le Jurassique, le Crétacé et le Paléocène (processus de dilatation thermique lors du rifting et de contraction thermique lors du refroidissement de la lithosphère, effondrement par flexure de la marge nord-africaine lors de la collision). Les géométries et densités obtenues sont comparées avec les données gravimétriques et de sismique réfraction.

Un des aspects du modèle de Wernicke (1985), la dissymétrie du rifting de la marge africaine, semble se vérifier par l’analyse et à la modélisation de la subsidence. Mais celle-ci montre l’existence d’une fusion adiabatique tardive du manteau supérieur dont le modèle de cisaillement simple ne tient pas compte. Le soulèvement de la marge à la fin du rifting ne serait pas dû uniquement à une dilatation thermique car les données de terrain montrent des discordances angulaires importantes sur la marge africaine. Ce soulèvement est attribué localement à la poussée des rides médio-océaniques naissantes de l’Atlantique et du sillon transformant nord-africain.

La modélisation de la subsidence tectonique permet d’expliquer l’absence d’intumescence sous le Rif. Elle est attribuée aux taux d’amincissement crustaux élevés durant les phases d’extension triasico-jurassiques. Cette approche quantitative confirme l’existence d’un bassin intra-continental avorté au sud-ouest et d’une marge continentale sensu stricto au nord-est. Si l’océanisation paraît plus tardive dans la partie rifaine du sillon transformant nord-africain (Callovien) que dans l’Atlantique Central (Bajocien), la subsidence post-rift ne se distingue pas de celle d’une marge passive classique.  相似文献   

燕辽地区长城系串岭沟组及团山子组沉积时代的新制约   总被引：18，自引：15，他引：3  

张拴宏  赵越  叶浩  胡健民  吴飞 《岩石学报》2013,29(7):2481-2490

华北克拉通北部燕辽地区是长城系地层出露最全的标准建组地区之一.近年来研究结果表明长城系地层底界年龄比以往所认为的18亿年明显年轻.新的锆石LA-ICP-MS U-Pb测年结果显示,平谷熊耳寨团山子组上部钾质火山岩的锆石207 Pb/206 Pb加权平均年龄为1637±15Ma(95％置信度,N=15,MSWD=0.75),一致年龄为1641±4Ma(1σ,N=14,MSWD=0.12),限定了团山子组上部的沉积时代.蓟县青山岭侵位于串岭沟组地层内闪长玢岩脉的锆石207 Pb/206Pb加权平均年龄为1634±9Ma(95％置信度,N=17,MSWD=0.40),表明串岭沟组地层沉积发生在1634±9Ma之前.结合前人大红峪组火山岩的研究结果还表明,燕辽拗拉槽(裂谷)钾质火山岩的喷发开始于1637±15Ma,在大红峪期(～1625Ma)达到高潮.  相似文献   

Sequence Stratigraphy and Evolution of the Neoproterozoic Marginal Basins Along Southeastern Yangtze Craton, South China     

Jian Wang  Zheng-Xiang Li 《Gondwana Research》2001,4(1)

Four sequence sets have been recognized in the Neoproterozoic basins along the southeastern margin of the Yangtze Craton, South China. The first sequence set consists of the Baizhu and Hetong Formations (or their equivalents), which is absent or partially absent in the denudational areas of the Jiangnan Ridge division. It represents the beginning of the continental rifting. The second sequence set is made up of the Sanmenjie and Gongdong Formations (or their equivalents), and is characterised by widespread rift volcanism. The third sequence set is represented by the Chang'an Formation glacial deposits in the Hunan-Guangxi sub-basin, which is absent in land areas covered by continental ice sheets. The Nantuo tillites and subsequent carbonaceous and siliceous sediments (the Doushantuo and Dengying Formations) constitute the fourth sequence set in the study area, marking the end of the continental rifting. The first three sets have been interpreted as forming the rift-fill, and the last one the rift cover. This study is the first step towards a better understanding of the Neoproterozoic basin history in South China, and a more robust correlation with Neoproterozoic successions in other continents formed during the breakup of Rodinia.  相似文献   

Zircon U-Pb Ages and Lu-Hf Isotopes for Negative to Low δ18O Magmatic Rocks of Neoproterozoic Age in South China     

ZHANG Shaobing  ZHENG Yongfei 《《地质学报》英文版》2013,87(Z1):286-288

  相似文献   

Evolution of the Western Margin of Australia during the Rodinian and Gondwanan Supercontinent Cycles     

S.A. Wilde 《Gondwana Research》1999,2(3):481

The proto-Darling Fault zone and its successor, the Darling Fault, extend for 1, 000 km along the western continental margin of Australia and appear to have been active at several periods during the geological past. Deformation commenced at 2,570 Ma and affected Late Archaean granitoids along the western margin of the Yilgarn Craton. Much of the later activity reflects events related to the accretion and breakup associated with the Rodinia and Gondwanaland supercontinent cycles.In the north, rocks of the Northampton and Mullingarra Complexes form part of a high-grade Grenvillian orogenic belt lying to the west of the Darling Fault, referred to as the Pinjarra Orogen. They underwent granulite facies metamorphism 1080 Ma ago and form part of the global collisional event that resulted in the amalgamation of Rodinia. These rocks extend southward beneath Phanerozoic sedimentary cover (the Perth Basin), where they are constrained to the east by the Darling Fault and to the west by the Dunsborough Fault, the latter marking the eastern boundary of the Leeuwin Complex.The Leeuwin Complex is a fragment of Pan-African crust that has traditionally been considered part of the Pinjarra Orogen. It is composed predominantly of upper amphibolite to granulite facies felsic orthogneisses derived from A-type, anorogenic granitoids. Conventional and SHRIMP U-Pb zircon geochronology has established that the granitoids evolved between 780 Ma and 520 Ma and were metamorphosed at 615 Ma. These events are equated with rifting associated with the breakup of Rodinia. Sm-Nd whole rock data support the juvenile nature of the crust and provide no evidence for the involvement of pre-existing Archaean continental material.During the Phanerozoic, the Dunsborough and Darling Faults were reactivated, as normal faults defining the inner arm of a major rift system within Eastern Gondwanaland and controlling sedimentation in the Perth Basin that now overlies the Grenvillian terrane. Major normal movement on the Darling Fault ceased by the Late Jurassic and it appears that continental breakup in the Early Cretaceous occurred along fractures closely related to the western boundary of the Leeuwin Complex that defined the eastern margin of the outer arm of the rift system. Breakup between Australia and Greater India commenced at 132 Ma and was followed by eruption of the Bunbury Basalt at 130 Ma and 123 Ma. This possibly resulted from hot spot activity beneath Eastern Gondwanaland and may have been a reflection of the Kerguelen plume, though the evidence is equivocal.It is argued from the petrographic, geochemical and isotopic characteristics, together with the likely contiguity of the Eastern Gondwanaland continents since the assembly of Rodinia, that the Leeuwin Complex evolved within an intracrustal rift and is not an exotic terrane. It is distinct from adjacent portions of the Pinjarra Orogen and should be considered a separate terrane. It is recommended that use of the term ‘Pinjarra Orogen’ be confined to rocks recording the Grenvillian events, thereby excluding those rocks (the Leeuwin Complex) that evolved during the later Pan-African orogeny.  相似文献   

康定杂岩锆石SHRIMP U-Pb定年及其地质意义   总被引：5，自引：4，他引：1  

赵俊香  陈岳龙  李志红 《现代地质》2006,20(3):378-385

康定杂岩在扬子地块西缘呈南北向带状分布,这套岩石岩性变化很大(从基性到中性、酸性),中性、酸性岩是组成该杂岩的主体。岩石类型有变辉长岩、闪长质片麻岩、石英闪长质片麻岩和花岗质片麻岩。康定杂岩以往被认为是扬子地块太古宇的基底,但近年来的同位素年龄测定结果表明其并不是形成于太古宙。本研究样品采自康定-泸定地区,挑选有代表性的两个样(样号71704.2、71501.1),对其进行岩石化学与微量元素分析及SHRIMP U-Pb测年。分析得出样品为钙碱性;原始地幔标准化微量元素分布型式显示相对富集大离子亲石元素K、Rb等,亏损高场强元素Nb、Ta、Ti、P等;稀土元素具有略向右倾的配分型式,且铕异常不明显,显示其具有与消减作用有关的岛弧火成岩的特征。锆石U-Pb分析给出的结晶年龄为765～771 Ma,w(Th)/w(U)大于0.1,具示岩浆成因特征。个别年轻的锆石颗粒,如71704.2中的12.1测点年龄为(430±8)Ma,可能是在后期构造、岩浆、变质作用中新形成的锆石,该年龄可解释为后期变质热事件的年龄。这些充分说明康定杂岩形成于新元古代,而非太古宙。此外,康定杂岩可能形成于岛弧环境,其岩浆主要起源于俯冲洋壳的熔融,结合其形成年龄说明扬子地块西缘新元古代岩浆活动可能是Rodinia超大陆裂解后的产物。  相似文献   

赣南陂头A型花岗岩的地质地球化学特征及其形成的构造环境   总被引：59，自引：10，他引：49  

范春方  陈培荣 《地球化学》2000,29(4):358-366

赣南陂头岩体主要钾长花岗岩组成,岩石为准铝质（ＡＮＫＣ＝０．９４～１．０７,平均０．９８）,富硅（ＳｉＯ２：７１．０６％～７６．２８％）,富碱（Ｎａ２Ｏ＋Ｋ２Ｏ：８．１％～９．８％）,ＦｅＯ＾Ｔ／ＭｇＯ（％）较高（９．６０～２２．００）,ＣａＯ和ＭｇＯ含量低（分别为０．５８％～１．１６％和０．０７％～０．２５％）,富含稀土元素（∑ＲＥＥ＝２７１．３６～７１７．７５μｇ／ｇ）和高场强元素（Ｙ、Ｚｒ、  相似文献   

大陆裂谷作用的物理模拟     

孙珍  周蒂  曾佐勋  钟志洪 《地质科技情报》2000,19(1):23-26

裂谷作用的物理模拟是研究大陆裂谷系统的几何结构与动力学机制之间关系的一种直观有效的手段。对正向裂谷作用、斜向裂谷作用以及两期作用先后叠加模拟过程中,断裂系统发育的特征进行了综述。目前这些实验结果已被用于解释天然裂谷的形式,并根据断层方向的统计分析推导伸展向量的大致方向。  相似文献   

Structures of the Bohai Petroliferous Area, Bohai Bay Basin   总被引：3，自引：0，他引：3  

CAI Dongsheng  LUO Yuhui  YAO Changhu  Research Institute of the Bohai Corporation of CNOOC  Tianjin HE Jiankun  HU Shengbiao  Institute of Geology  Geophysics  Chinese Academy of Sciences  Beijing LU Huafu  WANG Liangshu Department of Earth Sciences  Nanjing University  Nanjing  Jiangsu 《《地质学报》英文版》2000,74(3):641-650

This paper, for the first time, deals with a more systematic study of the structures in the Bohaipetroliferous area that covers nearly one third of the Bohai Bay basin. The study mainly involves the effects of preexisting basement faults on the basin formation, the characteristics of basin geometry and kinetics, the modelling of the tectonic-thermal history, the polycyclicity and heterogeneity in the structural evolution and the natural seismic tomographic images of the crust and upper mantle. The authors analyze the features of the dynamic evolution of the basin in the paper and point out that the basin in the Bohai petroliferous area is an extensional pull-apart basin.  相似文献