Geological interpretation of a deep seismic‐reflection transect across the boundary between the Delamerian and Lachlan Orogens,in the vicinity of the Grampians,western Victoria     

R. J. Korsch  T. J. Barton  D. R. Gray  A. J. Owen  D. A. Foster 《Australian Journal of Earth Sciences》2013,60(6):1057-1075

A deep seismic‐reflection transect in western Victoria was designed to provide insights into the structural relationship between the Lachlan and the Delamerian Orogens. Three seismic lines were acquired to provide images of the subsurface from west of the Grampians Range to east of the Stawell‐Ararat Fault Zone. The boundary between the Delamerian and Lachlan Orogens is now generally considered to be the Moyston Fault. In the vicinity of the seismic survey, this fault is intruded by a near‐surface granite, but at depth the fault dips to the east, confirming recent field mapping. East of the Moyston Fault, the uppermost crust is very weakly reflective, consisting of short, non‐continuous, west‐dipping reflections. These weak reflections represent rocks of the Lachlan Orogen and are typical of the reflective character seen on other seismic images from elsewhere in the Lachlan Orogen. Within the Lachlan Orogen, the Pleasant Creek Fault is also east dipping and approximately parallel to the Moyston Fault in the plane of the seismic section. Rocks of the Delamerian Orogen in the vicinity of the seismic line occur below surficial cover to the west of the Moyston Fault. Generally, the upper crust is only weakly reflective, but subhorizontal reflections at shallow depths (up to 3 km) represent the Grampians Group. The Escondida Fault appears to stop below the Grampians Group, and has an apparent gentle dip to the east. Farther east, the Golton and Mehuse Faults are also east dipping. The middle to lower crust below the Delamerian Orogen is strongly reflective, with several major antiformal structures in the middle crust. The Moho is a slightly undulating horizon at the base of the highly reflective middle to lower crust at 11–12 s TWT (approximately 35 km depth). Tectonically, the western margin of the Lachlan Orogen has been thrust over the Delamerian Orogen for a distance of at least 25 km, and possibly over 40 km.  相似文献   

Mesoproterozoic Fraser Complex: Geochemical evidence for multiple subduction‐related sources of lower crustal rocks in the Albany‐Fraser Orogen,Western Australia     

K. C. Condie  J. S. Myers 《Australian Journal of Earth Sciences》2013,60(6):875-882

The 1300 Ma Fraser Complex in the Albany‐Fraser Orogen of Western Australia is a thrust stack of mainly gabbroic rocks metamorphosed to granulite facies. This package of fault‐bounded units was elevated from a deep crustal level onto the margin of the Yilgarn Craton during continental collision between the Mawson and Yilgarn Cratons. Incompatible trace‐element distributions demand at least three mantle sources. Primitive‐mantle‐normalised incompatible‐element distributions show strong negative Ta–Nb anomalies, typical of subduction‐derived magmas. Three lines of evidence indicate that the mafic magmas did not acquire these anomalies by assimilation of crustal rocks: (i) major‐element compositions do not allow appreciable contamination with felsic material; (ii) Ni contents of many mafic rocks are too high for a significant contribution from a felsic assimilant; and (iii) Sr and Nd isotopic data support a largely juvenile source for the magmas that produced the Fraser Complex. Hence, the Ta–Nb anomalies are interpreted to reflect subduction‐related magmatic sources. On multielement diagrams, depletions in Sr, Eu, P, and Ti can be explained by fractional crystallisation, whereas Th and Rb depletions in many of the Fraser Complex rocks probably reflect losses during granulite‐facies metamorphism. These results suggest that the lower crust in this region at 1300 Ma was dominantly of arc origin, and there is no evidence to support mantle plume components. The Fraser Complex is interpreted as remnants of oceanic arcs that were swept together and tectonically interleaved with the margin of the Mawson Craton just before, or during, collision with the Yilgarn Craton at 1300 Ma.  相似文献   

安徽金寨银水寺铅锌矿床流体包裹体和同位素地球化学特征     

吴皓然  谢玉玲  钟日晨  王莹  安卫军 《大地构造与成矿学》2019,43(5):967-990

银水寺铅锌矿床位于大别造山带北缘,是该区最大的矽卡岩型矿床。矿体主要发育在中元古界庐镇关岩群仙人冲组大理岩与郑堂子组千枚岩之间的层间破碎带以及正长花岗斑岩与大理岩的接触带中。矿床先后经历了四个成矿阶段,矽卡岩阶段(Ⅰ)、石英.白钨矿阶段(Ⅱ)、石英.硫化物阶段(Ⅲ)、碳酸盐阶段(Ⅳ)。矽卡岩阶段(Ⅰ)主要发育绿帘石、阳起石、石英、绿泥石、磁铁矿及少量金属硫化物等;石英.白钨矿阶段(Ⅱ)主要发育石英、方解石、萤石及少量白钨矿和金属硫化物;石英.硫化物阶段(Ⅲ)广泛发育闪锌矿、方铅矿、黄铜矿等金属硫化物及石英、方解石、萤石、绿泥石等;碳酸盐阶段(Ⅳ)主要发育方解石、石英及少量黄铁矿。矿床中发育三种类型流体包裹体,包括富CO2水溶液包裹体(AC类)、气液两相水溶液包裹体(L类)和含子晶多相包裹体(S型)。根据流体包裹体岩相学、显微测温、激光拉曼研究结果,矽卡岩阶段主要有富CO2包裹体和气液两相水溶液包裹体,均一温度为314~400℃、盐度变化范围较大(1.1%~19.3%NaCleqv);石英.白钨矿阶段发育气液两相水溶液包裹体、含子晶多相包裹体和富CO2包裹体,后两者均一温度相近(263~349℃)、盐度差异较大(32.8%~41%NaCleqv和0.8%~6.1%NaCleqv),表明流体发生了沸腾作用;石英.硫化物阶段主要发育气液两相水溶液包裹体,均一温度为230~332℃,盐度为0.2%~8.9%NaCleqv;碳酸盐阶段只发育气液两相水溶液包裹体,显示低温(162~245℃)、低盐度(0.2%~5.6%NaCleqv)的特征。矿床不同成矿阶段石英、绿帘石中流体包裹体中水H-O同位素研究结果表明,δ18Ofluid值从早到晚逐渐减小,其中矽卡岩阶段为–1.3‰~4.7‰、石英.硫化物阶段为–5.1‰~–3.1‰,表明银水寺矿床早期成矿流体主要为岩浆来源,并在成矿过程中不断有大气降水的加入。石英流体包裹体中CO2的C同位素测试结果表明,矽卡岩阶段δ13CV-PDB值为–9.2‰,石英.硫化物阶段为–25.8‰~–15.4‰,表明早期成矿流体中碳质主要来自岩浆,石英-硫化物阶段有大量有机碳加入,其可能与流体和富含有机质的地层反应有关。矿石中主要金属硫化物的δ34S值(1.7‰~4.4‰)显示了深源硫的特征。Pb同位素变化范围集中(206Pb/204Pb=16.55~16.705,207Pb/204Pb=15.369~15.459,208Pb/204Pb=37.463~37.767),显示壳幔混源的特点。随着成矿作用的进行,岩浆流体与碳酸盐围岩地层发生水岩交代反应形成矽卡岩,该过程造成了成矿矽卡岩阶段磁铁矿和少量闪锌矿的沉淀;断裂活动造成热液体系压力下降,流体发生沸腾,CO2、HF进入气相并逃逸促使矿床中钨的沉淀;同时大气降水沿裂隙灌入,混合作用导致流体的温度、盐度降低,Cl–浓度下降,造成矿床中铅锌的大面积沉淀。  相似文献   

Deep crustal structures of eastern China and adjacent seas revealed by magnetic data   总被引：5，自引：0，他引：5  

ChunFeng Li  Bing Chen  ZuYi Zhou 《中国科学D辑(英文版)》2009,52(7):984-993

Through reduction to the North Pole and upward continuation of the total field magnetic anomalies, we analyze magnetic patterns and spatial distributions of different tectonic blocks and crustal faults in eastern China and adjacent seas. Depths to the Curie isotherms are further estimated from radially averaged amplitude spectra of magnetic data reduced to the pole. Data reductions effectively enhance boundaries of regional tectonic belts, such as the Dabie ultra-high metamorphic belt, the Tanlu Fault, and the Diaoyudao Uplift. Curie depths are estimated at between 19.6 and 48.9 km, with a mean of 31.7 km. The Subei Basin and the south Yellow Sea Basin in the lower Yangtze block show relatively deep Curie isotherms, up to about 35 km in depth, whereas in the surrounding areas Curie depths are averaged at about 25 km. This implies that the lower Yangtze Block has experienced a unique tectonic evolution and/or has unique basement lithology and structures. From a regional perspective, sedimentary basins, such as the Subei Basin, the south Yellow Sea Basin, and the East China Sea Basin, normally show deeper Curie isotherms than surrounding uplifts such as the Diaoyudao Uplift and the Zhemin Uplifts. Curie isotherms also upwell significantly in volcanically active areas such as the Ryukyu Arc and the Cheju Island, confirming strong magmatic and geothermal activities at depth. Supported by National Natural Science Foundation of China (Grant Nos. 40776026 and 40876022) and National Basic Research Program of China (Grant No. 2007CB411702)  相似文献   

北祁连山银灿铜矿矿床地质特征及成因   总被引：2，自引：2，他引：0       下载免费PDF全文

郭周平  赵辛敏  白赟 《中国地质调查》2015,2(3):54-58

银灿铜矿地处于北祁连走廊南山北坡—冷龙岭岛弧带中,矿区出露一套具双峰式火山岩特征的火山沉积建造,矿体主要赋存在石英角斑岩中并存在明显分带,上部为铜矿体向下部变为锌矿体,矿石类型属黄铁矿型多金属矿石,成矿作用过程直接或间接与火山活动有关,是北祁连地区早古生代典型的海相火山岩型块状硫化物矿床。  相似文献   

东昆仑西段其木来克一带晚二叠世侵入岩的成因及其构造意义     

陈邦学  徐胜利  杨有生  周能武  朱志新 《地质通报》2019,38(6):1040-1051

对东昆仑其木来克一带的花岗质岩体进行锆石U-Pb测年,获得花岗闪长岩年龄为274.6±1.2Ma,黑云母花岗岩闪长岩年龄271.2±0.6Ma,认为其形成于晚二叠世。该岩体的地球化学特征显示,其具有钙碱性、弱过铝质(A/CNK=0.99～1.1)特征;稀土元素球粒陨石标准化分布图表现为左陡右缓,具弱的负Eu异常;微量元素特征显示高场强元素Nb、Ta、Ti、P等亏损,结合构造环境认为其形成于岛弧环境,属于I型花岗岩。结合区域构造演化,认为古特提斯洋于晚二叠世开始向塔里木板块俯冲,与此同时洋中脊还在持续扩张,表明此时的特提斯洋已处于消亡期。  相似文献   

河南省济源盆地下侏罗统鞍腰组重力流沉积特征及其构造意义^*          下载免费PDF全文

杨文涛  吴蒙  杨旅涵  史飞  梁厅 《古地理学报》2017,19(3):433-444

在详细野外剖面工作的基础上,通过岩性特征、沉积构造及沉积序列等的系统观察研究,发现济源盆地下侏罗统鞍腰组重力流沉积由滑塌沉积、砂质碎屑流沉积和浊流沉积构成。滑塌沉积以砂岩和泥岩的混杂、岩层的滑动变形以及泥岩呈碎块被卷入砂岩层中为特征;砂质碎屑流沉积常呈厚层块状,颗粒分选和磨圆较差,杂基较多,可见漂浮于层内的石灰岩砾石;常见的浊流沉积分为2种类型: 具有明显正粒序结构的浊流沉积和砂泥岩薄互层的浊流沉积,可用鲍马序列来描述。鞍腰组重力流沉积可划分为3个沉积序列: 序列A记录了滑塌沉积→砂质碎屑流沉积→浊流沉积→深湖沉积的转换过程;序列B表现为砂质碎屑流与浊流沉积的叠覆;序列C由浊流及湖泊沉积构成,并经历了由序列A→序列B→序列C的沉积演化过程。重力流的形成受秦岭造山带于早侏罗世沿三门峡—鲁山—舞阳断裂发生逆冲推覆作用的控制,其沉积演化指示了秦岭造山带造山作用由强到弱的过程。  相似文献   

Chronological constraints on the tectonic evolution of the Chinese Tianshan Orogen through detrital zircons from modern and palaeo-river sands     

Rong Ren  Shu-Wei Guan  Bao-Fu Han  Li Su 《International Geology Review》2017,59(13):1657-1676

The Chinese Tianshan Orogen marks prolonged and complicated interactions between the southwestern Palaeo-Asian Ocean and surrounding blocks. New and previously published detrital zircon chronological data from modern and palaeo-river sands were compiled to reveal its tectonic evolution. It is characterized by predominant Palaeozoic as well as minor Mesozoic and Precambrian detrital zircon ages with a multimodal characteristic. The oldest Phanerozoic zircon population (peaking at 475 Ma) is a result of subduction and closure of the early Palaeozoic Terskey Ocean. However, the absence of this peak in the Chinese North and southern South Tianshan suggests that subductions of the North and South Tianshan oceans may not have initiated until the Late Ordovician with subsequent 460–390 and 360–320 Ma arc magmatism. Similar to the magmatic suite in classic collisional orogens, the youngest massive 320–270 Ma magmatism is suggested to be post-collisional. The North and South Tianshan oceans therefore probably had their closure to form the Chinese Tianshan Orogen during the late Carboniferous. The weak Mesozoic intra-plate magmatism further rejects a late Permian–Triassic Tianshan Orogen due to a lack of extensive syn- and post-collisional magmatism. Moreover, diverse Precambrian detrital zircon age patterns indicate that the surrounding blocks have distinct evolutionary processes with short-term amalgamation during the Meso- to Neoproterozoic.  相似文献   

Detrital zircon U–Pb ages and whole-rock geochemistry of the Neoproterozoic Paulistana and Santa Filomena complexes,Borborema Province,northeastern Brazil: implications for source area composition,provenance, and tectonic setting     

Felipe H. Santos  Wagner S. Amaral  Evilarde C. Uchôa Filho  Douglas T. Martins 《International Geology Review》2017,59(15):1861-1884

The Paulistana and Santa Filomena Complexes are situated in the southern part of the Borborema Province (northeastern Brazil), in the Riacho do Pontal Orogen, and represent meta-volcano-sedimentary sequences. We present compositional variations in the metasedimentary rocks and new U–Pb detrital zircon data. Major and trace elements indicate that the metasedimentary rocks from the Paulistana and Santa Filomena Complexes are composed mostly of immature to mature sediments derived from felsic-intermediate sources with moderate to slightly high chemical weathering. The geochemical signatures of the sediment protoliths for both complexes are characteristic of continental magmatic arc settings with minor contribution from recycled sediment sources. The source area for the Paulistana Complex rocks follow the compositional trend between calc-alkaline granites and granodiorites, whereas the Santa Filomena Complex rocks have a more restricted composition trending to more granodioritic sources. For the Paulistana Complex, two main source ages were identified: (1) Tonian (ca. 950 Ma – sample RPE-58) and Tonian–Stenian (ca. 1.0 Ga – sample RPE-103). These data coupled with geochemical information suggest that the Cariris Velhos arc system was the main source area for the Paulistana Complex. Regarding the Santa Filomena metasedimentary rocks, potential source-areas include: (1) Neoarchaean rocks (~2.6 Ga) represented by the adjacent basement rocks of the Riacho do Pontal Orogen; (2) Rhyacian–Orosirian rocks (2.2–2.0 Ga) of the Riacho do Pontal Orogen and the Pernambuco–Alagoas terrain, which include an augen-gneiss with arc-related geochemical signature; (3) Statherian granites (1.7–1.6 Ga); and (4) Cariris Velhos crust (1000–920 Ma). The metasedimentary rocks of the Paulistana Complex were deposited in a rift stage (ca. 900 Ma), which is related to the break-up of the Rodinia supercontinent. The metasedimentary rocks of the Santa Filomena Complex most probably were deposited in another rift stage (ca. 750–700 Ma) and could be correlatives of the rift formation of the Canindé Domain (Sergipano Orogen).  相似文献   

Reconstructing the Cryogenian–Ediacaran evolution of the Porongos fold and thrust belt,Southern Brasiliano Orogen,based on Zircon U–Pb–Hf–O isotopes     

J. Pertille  L. A. Hartmann  J. O. S. Santos  N. J. McNaughton  R. Armstrong 《International Geology Review》2017,59(12):1532-1560

The Neoproterozoic geotectonic triad of the Brasiliano Orogen is reconstructed in southern Brazil from studies focused on the Porongos fold and thrust belt. We integrate field geology with isotopic studies of zircon U–Pb SHRIMP and Lu–Hf–O laser determinations in seven metasedimentary and three metavolcanic rock samples. The results indicate that the Porongos palaeo-basin was derived from mixed sources (3200–550 Ma), with major contributions from Rhyacian (2170 Ma) and Ediacaran (608 Ma) sources. Minor contributions from Archaean to Tonian sources are also registered. The maximum depositional age of the Porongos palaeo-basin is established by the age range of 650–550 Ma with T_DM model ages between 2.5 and 1.3 Ga. The reworked signature (ε_Hf values = ?34 to ?4) and the characteristic crustal magma reservoirs (δ¹⁸O ≥5.3 ‰) indicate that these sediments are equivalent to Neoproterozoic granites of the Dom Feliciano Belt. The episodic depositional history started in the Cryogenian (650 Ma) and lasted until the Ediacaran (most likely 570 Ma). A magmatic event of Tonian age is recorded in rhyodacite samples interleaved with the metasedimentary rocks and dated at 773, 801, and 809 Ma. The crustal evolution of the Sul-Riograndense Shield included mountain building, folding and thrusting and flexural subsidence in the foreland. An orogenic triad is revealed as the Pelotas Batholith, the Porongos fold and thrust belt and the Camaquã Basin, all part of the Dom Feliciano Belt.  相似文献