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1.
A. V. Maslov M. V. Isherskaya M. T. Krupenin V. G. Petrishcheva T. Ya. Gulyaeva N. P. Gorbunova 《Lithology and Mineral Resources》2010,45(2):172-200
Lithogeochemical features of Riphean fine-grained terrigenous rocks of the Kama-Belaya aulacogen are discussed. It is shown
that aluminosiliciclastic material delivered to the aulacogen during the Riphean was characterized by a low maturity degree.
The successively increasing K2O/Al2O3 values in the Riphean summary section correlate negatively with the CIA index values, indicating a gradually strengthening
tendency for climate aridization in erosion zones. Data on some indicator ratios of trace elements and REE systematics in
Riphean silty mudstones and shales of the Kama-Belaya aulacogen imply the involvement of mafic and ultramafic rocks, in addition
to acid igneous and metamorphic varieties, in erosion during accumulation of the Nadezhdino, Tukaevo, Ol’khovka, Usinsk, and
Priyutovo formations. Comparison of data on the composition of rocks in provenances based on the mineralogical-petrographic
study of sandstones and investigation of geochemical features of silty mudstones and shales revealed their sufficiently high
similarity. The geochemical data made it possible to specify the composition of rocks in provenances. Low Ce/Cr values in
the fine-grained terrigenous rocks of the Lower Riphean Kyrpy Group suggest their formation with a significant contribution
of erosion products of the Archean substrate, which is atypical for higher levels of the section. Thus, the Early-Middle Riphean
transition period was likely marked by substantial changes in the mineral composition of material delivered to the Kama-Belaya
aulacogen. The lack of exhalative components in the examined specimens of silty mudstones and shales points to a relatively
low permeability of the Earth’s crust in the eastern East European Platform through the entire Riphean. 相似文献
2.
Lithogeochemical features of the Vendian mudstones and silty mudstones taken from Borehole Keltma 1 in the southern part of
the Vychegda trough of the Mezen syneclise are discussed. It is shown that fine-grained clastic rocks of the Ust-Pinega, Krasavino,
and Mezen formations have similar chemical compositions, suggesting their accumulation in sufficiently similar settings. The
main part of the studied samples has K2O/Al2O3 < 0.4. This fact, in combination with the absence of TM-FM and NPM-HM correlations, indicates a significant contribution
of recycled aluminosiliciclastics in their composition. At the same time, the absence of correlation between CIA and indicator
ratios of rock composition in the paleodrainage basins, such as Th/Cr and Th/Sc, indicates that CIA and some other lithochemical
indicators appropriately reflect the paleoclimatic conditions in source areas surrounding a basin. The CIA value in most of
the analyzed samples is no more than 70. Thus, the Keltma section is similar to Upper Vendian sequences of the Kvarkush-Kamennogorsk
anticlinorium and the Shkapovo-Shikhany depression. It has been established that felsic and intermediate magmatic rocks coupled
with a significant contribution of quartz-rich sediments served as the source of fine aluminosiliciclastics for the southern
Vychegda trough during the Vendian. High Ce/Cr values in the mudstones and silty mudstones suggest that the geochemically
primitive Archean protoliths were not involved in the washout. In the SiO2-K2O/Na2O diagram, the Vendian mudstones and silty mudstones are plotted in the field of sediments of active continental margins.
Typical low values of Mo/Mn and some other redox indices in these rocks indicate that oxidizing environment predominated in
bottom waters of the sedimentation basin during the entire Vendian. Analysis of variations of the lithochemical indicators
upward the Vendian sedimentary successions in borehole Keltma 1 made it possible to divide the section into three sequences
of different lithofacies and paleontological compositions. 相似文献
3.
The paper reports data on the lithogeochemistry of sandstones and silty mudstones from Upper Vendian sedimentary sequences in the northeastern, eastern, and southwestern peripheries of the East European Platform belonging to the so-called unfolded molasse. The sequences are dominated by wackes, arkoses, subarkoses, litharenites, and sublitharenites, i.e., chemically immature and moderately mature psammites, and can be classed with rocks produced by clastic material brought from orogens surrounding the platform. The higher TiO2, Al2O3, FeOtot, MgO, Na2O, and K2O concentrations of the psammites than those in the average cratonic Phanerozoic sandstone (APhSa) testify that the chemical maturing of the rocks was not completed. The silty mudstones accompanying the sandstones have a composition closer to those of the average cratonic Phanerozoic shale (APhSh), but this is likely explained by the fact that the rocks were produced of material brought from erosion territories of much greater area. The lithogeochemical data generally indicate that these territories were dominated by acid and intermediate magmatic rocks with variable fraction of sedimentary rocks when the Late Vendian sedimentary associations in question were produced. The distribution of certain indicator trace elements in the sandstones and silty mudstones show that the average composition of the eroded complexes was close to the composition of the post-Archean upper continental crust, but the erosion areas occasionally (in the Vychegorskii trough and the Shkapovsko-Shikhanskaya depression) contained relatively primitive source rocks. The data points of the great majority of the sandstones and silty mudstones plot in the SiO2-K2O/Na2O and F1–F2 diagrams in the fields of sediments typical of the environments of active continental margins, which is consistent with the arrangement of the data points of these rocks in the La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 diagrams. All of these features confirm that the sedimentary rocks in question affiliate with rock associations produced at an active tectonic regime. 相似文献
4.
The lithological-stratigraphic study of volcanogenic-siliceous rocks developed on the left side of the Machtovaya River, a right tributary of the Amur River, yielded the first radiolarian assemblages of the late Late Tithonian, the late Late Tithonian-early Valanginian, and the middle-late Albian age. It is established that the stratigraphic succession of volcanogenic-siliceous rocks in this area is composed of upper Tithonian-Valanginian dark red to red-brown cherts with basalts in the lower part of the section and Albian dark gray clayey cherts, olive-gray siliceous-tuffaceous argillites, and tufaceous siltstones in its upper part. The replacement of cherts by their clayey varieties likely occurred in the Aptian. The composition, structure, and age of these strata and the rocks constituting the Kiselevka-Manoma accretionary complex are different, which indicates their different tectonic origin. 相似文献
5.
Gweltaz Maho Xavier Fayoux Stphane Guillot Eduardo Garzanti Paul Capiez Georges Mascle 《Journal of Asian Earth Sciences》2006,26(6):695-707
In the Ladakh–Zanskar area, relicts of both ophiolites and paleo-accretionary prism have been preserved in the Sapi-Shergol mélange zone. The paleo-accretionary prism, related to the northward subduction of the northern Neo-Tethys beneath the Ladakh Asian margin, mainly consists of tectonic intercalations of sedimentary and blueschist facies rocks. Whole rock chemical composition data provide new constraints on the origin of both the ophiolitic and the blueschist facies rocks. The ophiolitic rocks are interpreted as relicts of the south Ladakh intra-oceanic arc that were incorporated in the accretionary prism during imbrication of the arc. The blueschist facies rocks were previously interpreted as oceanic island basalts (OIB), but our new data suggest that the protolith of some of the blueschists is a calc-alkaline igneous rock that formed in an arc environment. These blueschists most likely originated from the south Ladakh intra-oceanic arc. This arc was accreted to the southern margin of Asia during the Late Cretaceous and the buried portion was metamorphosed under blueschist facies conditions. Following oceanic subduction, the external part of the arc was obducted to form the south Ladakh ophiolites or was incorporated into the Sapi-Shergol mélange zone. The incorporation of the south Ladakh arc into the accretionary prism implies that the complete closure of the Neo-Tethys likely occurred by Eocene time. 相似文献
6.
7.
The Guarguardz Complex, basement of the Cordillera Frontal, included in the proposed Chilenia Terrane, consists of metasedimentary rocks deposited in clastic and carbonatic platforms. Turbiditic sequences point out to slope or external platform environments. According to geochemical data, the sedimentary protoliths derived through erosion of a mature cratonic continental basement. Volcanic and subvolcanic rocks with N and E-MORB signature were interbeded in the metasedimentary rocks during basin development. A compressional stage, starting with progressive deformation and metamorphism, followed this extensional stage. Continuing deformation led to the emplacement of slices of oceanic crust, conforming an accretionary prism during Late Devonian. The Guarguardz Complex and equivalent units in western Precordillera and also in the Chilean Coastal Cordillera share common evolutional stages, widely represented along the western Gondwana margin. These evidences imply that Chilenia is not an allochthonous terrane to Gondwana, but a portion of its Early Paleozoic margin. Regional configuration indicates that the Guarguardz Complex and equivalent units represent the accretionary prism of the Famatinian arc (Middle Ordovician-Late Devonian). 相似文献
8.
Ophiolites of the Afrika Mys Block of the Kamchatsky Mys Peninsula, eastern Kamchatka, are a fragment of an accretionary prism that formed in the Late Cretaceous-Eocene on the southern side of the Kronotsky island arc as a result of its collision with the Smagino volcanic uplift that arose at the post-Neocomian time on the subducting plate. On the basis of the geologic, geochemical, and paleomagnetic data available to date, it is established that ophiolites are heterogeneous in their origin and were formed in different geodynamic settings that changed progressively with time. The heterogeneous structure of ophiolites displays the evolution of a fragment of the oceanic lithosphere, which was not submerged into subduction zone, from its origination in the spreading center via transformation under conditions of the plume-related volcanic uplift to the involvement in the structure of the Kronotsky island arc, which is currently a constituent of the accretionary system of Kamchatka. The reconstruction of ophiolites tectonically fragmented in the accretionary prism allows recognition of (1) derivatives of an ocean ridge (ultramafic-gabbro-basaltic complex of the Mount Olen’ya Massif) conjugated with a transform fault and volcanosedimentary rocks of the Smagino volcanic uplift (cover of the oceanic crust) and (2) a fragment of the lithospheric mantle (ultramafic rocks of the Lake Stolbovoe Massif) exhumed in the process of collision and genetically related to the evolution of the volcanic uplift. In the course of evolution of the Kronotsky island arc, all these elements were overlapped by tephrogenic turbidites (Pikezh Formation) and quartz-feldspar graywackes (Pikezh Sandstone) that were involved in the accretionary prism as well. The paleotectonic reconstructions broadly support the petrologic conclusions about the complementary nature of different igneous complexes and ascertain the temporal sequence of events. 相似文献
9.
The results of study of the Ishkinino Co-Cu massive sulfide deposit hosted in ultramafic rocks of the Main Ural Fault Zone are discussed. The ore field is localized in a fragment of Early Devonian accretionary prism composed of oceanic and island-arc tectonic sheets. The antiform structure of the ore field was formed at the collision stage in the Late Devonian. The primary ore was deposited near the bottom in the environment of the accretionary prism at the island-arc stage of evolution, whereas the superimposed ore mineralization was related to the collision stage. The primary ore is composed of massive, stringer-disseminated, and clastic varieties with two mineral assemblages of sulfides and oxides. The superimposed stringer-disseminated ore mineralization is represented by Co-Ni-Fe arsenides and sulfoarsenides, native gold, Bi and Te minerals, and late sulfides and oxides. Loellingite, safflorite, rammelsbergite, and krutovite were identified in the massive sulfide ore for the first time in the Urals. The geochemical attributes of Co-Ni minerals serve as indicators of superimposed processes. Chromites contained in rocks and ore correspond to Cr-spinel of suprasubduction ultramafic rocks in chemical composition. It is suggested that sulfide ore may be found in the accretionary prisms of the presently active island arcs composed of ultramafic sheets. 相似文献
10.
广西南部凭祥中三叠世沉积盆地构造环境——来自岩相学和碎屑岩地球化学的证据 总被引：2，自引：0，他引：2
岩相学特征表明,广西凭祥盆地砾岩可分为颗粒支撑和基质支撑2种,砾石成分主要为生物碎屑灰岩,其次为砂岩和泥岩。盆地砂岩主要由成分成熟度和结构成熟度较低的亚岩屑(杂)砂岩和岩屑(杂)砂岩组成,物源区为碰撞造山带或再旋回造山带。碎屑岩地球化学特征表明,凭祥中三叠世盆地中的砂岩和泥岩样品SiO2含量为61.71%~74.85%,接近于上地壳的平均值。具有高的K2O/Na2O值(6.50~0.51)和高的TFe2O3+MgO含量(7.29%~10.31%),TFe2O3/K2O值为2.05%~5.54%,矿物稳定性较差。稀土元素标准化配分曲线呈现出轻稀土元素富集、重稀土元素平坦和明显的Eu、Ce负异常特征,类似于上地壳和典型的太古宙页岩,具有海相沉积的特征。砂岩风化蚀变指数CIA高(71~88),Th/U值为3.68~9.53,表明砂岩和泥岩经历了较强的风化作用。砂岩物源区判别图表明,凭祥盆地物源与酸性岛弧具明显的亲缘性,增生楔和活动陆缘是主要的物源区。这些特征综合表明,凭祥盆地是一个伴随古特提斯分支洋盆闭合、经强烈构造改造的残余弧前盆地。 相似文献
11.
The Makran accretionary prism in southeastern Iran contains extensive Mesozoic zones of melange and large intact ophiolites, representing remnants of the Tethys oceanic crust that was subducted beneath Eurasia. To the north of the Makran accretionary prism lies the Jaz Murian depression which is a subduction-related back-arc basin. The Band-e-Zeyarat/Dar Anar ophiolite is one of the ophiolite complexes; it is located on the west side of the Makran accretionary prism and Jaz Murian depression, and is bounded by two major fault systems. The principal rock units of this complex are a gabbro sequence which includes low- and high-level gabbros, an extensive sheeted diabase dike sequence, late intrusive rocks which consist largely of trondhjemites and diorites, and volcanic rocks which are largely pillow basalts interbedded with pelagic sedimentary rocks, including radiolarian chert. Chondrite- and primitive-mantle-normalized incompatible trace element data and age-corrected Nd, Pb, and Sr isotopic data indicate that the Band-e-Zeyarat/Dar Anar ophiolite was derived from a midocean ridge basalt-like mantle source. The isotopic data also reveal that the source for basalts was Indian-Ocean-type mantle. Based on the rare earth element (REE) data and small isotopic range, all the rocks from the Band-e-Zeyarat/Dar Anar ophiolite are cogenetic and were derived by fractionation from melts with a composition similar to average E-MORB; fractionation was controlled by the removal of clinopyroxene, hornblende and plagioclase. Three 40Ar–39Ar plateau ages of 140.7±2.2, 142.9±3.5 and 141.7±1.0 Ma, and five previously published K–Ar ages ranging from 121±4 to 146±5 Ma for the hornblende gabbros suggest that rocks from this ophiolite were formed during the Late Jurassic–Early Cretaceous. Plate reconstructions suggest that the rocks of this complex appear to be approximately contemporaneous with the Masirah ophiolite which has crystallization age of (150 Ma). Like Masirah, the rocks from the Band-e-Zeyarat/Dar Anar ophiolite complex represent southern Tethyan ocean crust that was formed distinctly earlier than crust preserved in the 90–100 Ma Bitlis-Zagros ophiolites (including the Samail ophiolite). 相似文献
12.
QK-1天然气水合物钻探试验井位于西藏羌塘盆地毕洛错地区,主要钻遇中侏罗统夏里组粉砂质泥岩和布曲组灰岩。其有机质丰度、有机质类型、有机质成熟度等有机地球化学特征表明,南羌塘地区中侏罗统烃源岩的有机质丰度偏低,夏里组泥岩TOC介于0.26%~0.38%之间,达到差-中烃源岩标准,而布曲组灰岩TOC介于0.02%~0.08%之间,仅局部达到差烃源岩标准;两个组的烃源岩有机质类型主要为Ⅱ2型及Ⅲ型,较利于天然气的生成,其中夏里组的生气能力优于布曲组;该区烃源岩热演化程度较高,Ro为1.31%~1.63%之间,均达到高成熟阶段,而夏里组有可能已进入干气阶段。基于冻土区天然气水合物成藏条件分析,综合考虑夏里组烃源岩及沉积厚度特征,认为中侏罗统夏里组具备良好的天然气水合物勘探前景。 相似文献
13.
14.
I. K. Kozakov E. B. Salnikova V. P. Kovach I. V. Anisimova A. M. Fedoseenko S. Z. Yakovleva 《Stratigraphy and Geological Correlation》2013,21(5):482-495
The Early Caledonian folded area of Central Asia comprises a variety of continental crust fragments with Early to Late Precambrian crystalline basement. Crystalline rocks, which form part of the Songino block, outcrop at the junction between the Dzabkhan and Tuva-Mongolian terranes. The Bayannur zone in the southern part of the Songino block contains the Bayannur migmatite-gneiss and Kholbonur terrigenous-metavolcanic metamorphic complexes. Previous studies provide the 802 ± 6 Ma age for the regional metamorphism and folding within the Bayannur complex. On the basis of the minimum Nd model age of 1.5 Ga, gneisses from this complex cannot be regarded as Early Precambrian. Two main rock associations were distinguished in the Kholbonur complex. Mafic metavolcanics compose the dominant lithology of the first rock association, whereas the second association comprises terrigenous-volcanic and predominantly terrigenous suites. The rocks of the predominantly terrigenous suite, including mudstones, sandstones, and conglomerates, are interpreted to derive from the Late Riphean accretionary prism. The lithology and composition of metaterrigenous rocks suggest that they were possibly derived from erosion of a volcanic arc. The upper age limit of this suite is constrained by postkinematic granites (790 ± 3 Ma; U-Pb zircon), the lower age is given by plagiogranite (874 ± 3 Ma; U-Pb zircon) from comglomerate pebbles. Therefore, the timing of deposition of this terrigenous suite can be bracketed by the 874–790 Ma time interval. These ages and compositional features of the Kholbonur complex terrigenous rocks suggest that the convergence took place at around 870–880 Ma and thus it can be correlated with the divergent processes between the blocks of continental crust composing the supercontinent Rodinia. 相似文献
15.
I. P. Voinova 《Russian Journal of Pacific Geology》2016,10(3):230-238
The results of study of the volcanic rocks of the Khabarovsk accretionary complex, a fragment of the Jurassic accretionary prism of the Sikhote Alin orogenic belt (the southern part of the Russian Far East), are presented. The volcanic rocks are associated with the Lower Permian limestones in the mélange blocks and Triassic layered cherts. The petrography, petrochemistry, and geochemistry of the rocks are characterized and their geodynamic formation conditions are deduced. The volcanic rocks include oceanic plume basalts of two types: (i) OIB-like intraplate basalts formed on the oceanic islands and guyots in the Permian and Triassic and (ii) T(transitional)-MORBs (the least enriched basalts of the E-MORB type) formed on the midoceanic ridge in the Permian. In addition to basalts, the mélange hosts suprasubduction dacitic tuff lavas. 相似文献
16.
Yujiro Ogawa Ryota Mori Toshiaki Tsunogae Yildirim Dilek Ron Harris 《International Geology Review》2015,57(5-8):824-842
Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes. 相似文献
17.
The island of Ishigaki Jima, located in the western part of the southern Ryukyu Arc, Japan, is underlain by a basement comprising the Tumuru and Fu-saki formations. The former is a pelitic glaucophane schist with a metamorphic age of 220–190 Ma, and the latter is a weakly metamorphosed accretionary complex, composed mainly of chert, mudstone and sandstone with minor amounts of limestone and mafic rocks. The Fu-saki Formation was weakly metamorphosed at ∼140 Ma. Latest Carboniferous–Early Jurassic microfossils have been obtained from the limestones, cherts and siliceous mudstones of this formation, but no fossils have been collected from the phyllitic mudstones. The radiolarian fauna of the phyllitic mudstones described herein indicates a late Pliensbachian–early Toarcian (Early Jurassic) age. This result, when combined with existing data, enables the reconstruction of an oceanic plate stratigraphy, showing a succession of (in ascending order) Upper Carboniferous–Triassic cherts, Sinemurian–lower Pliensbachian siliceous mudstones and upper Pliensbachian–lower Toarcian phyllitic mudstones and sandstones. The radiolarians from the phyllitic mudstones are important in constraining the timing of the accretion of the Fu-saki Formation to the base of the Tumuru Formation. 相似文献
18.
Ji'en Zhang Wenjiao Xiao Chunming Han Songjian Ao Chao Yuan Min Sun Hongyan Geng Guochun Zhao Qianqian Guo Chong Ma 《Gondwana Research》2011,19(4):958-974
The Karamay area, situated in the eastern part of Western Junggar, Southern Altaids, contains an ophiolitic mélange with ultramafic rocks, gabbro, basalt, chert and limestone, which show typical block-in-matrix structures, and coherent turbidites and tuffs. These lithological associations are interpreted as incoherent and coherent series formed in an accretionary complex. On the basis of detailed field mapping and analyses of the asymmetry of imbricate thrusts, duplexes, tilted structures, shear band cleavages, and the NW-verging inclined to overturned folds, we conclude that the overall movement in the accretionary complex was top-to-the-NW. The youngest tuff involved in the deformation contains detrital zircons that have a U–Pb age (LA-MC ICP-MS) of 308 ± 7 Ma. 39Ar–40Ar resistance furnace step-heating of amphibole separates from a diorite dike, which cuts the folded and imbricated rocks in the accretionary prism, yielded a plateau age of 307 ± 2 Ma. Consequently, the age of the deformation in the prism is tightly constrained at 307–308 Ma, implying that the deformation occurred in an extremely short time-span during SE-ward subduction. Combined contemporaneous occurrence of Baogutu adakite, high-Mg, Sr-enriched and Y-poor dioritic dikes, Miaoergou charnockite, and Maliya mafic rocks, we further suggest the accretionary complex was cut by near-trench volcanic rocks and plutons possibly due to interaction with a spreading ridge. 相似文献
19.
S. V. Zyabrev 《Russian Journal of Pacific Geology》2011,5(4):313-335
The East Sakhalin accretionary wedge is a part of the Cretaceous-Paleogene accretionary system, which developed on the eastern
Asian margin in response to subduction of the Pacific oceanic plates. Its formation was related to the evolution of the Early
Cretaceous Kem-Samarga island volcanic arc and Late Cretaceous-Paleogene East Sikhote Alin continental-margin volcanic belt.
The structure, litho-, and biostratigraphy of the accretionary wedge were investigated in the central part of the East Sakhalin
Mountains along two profiles approximately 40 km long crossing the Nabil and Rymnik zones. The general structure of the examined
part of the accretionary wedge represents a system of numerous east-vergent tectonic slices. These tectonic slices. tens to
hundreds of meters thick. are composed of various siliciclastic rocks, which were formed at the convergent plate boundary,
and subordinate oceanic pelagic cherts and basalts, and hemipelagic siliceous and tuffaceous-siliceous mudstones. The siliciclastic
deposits include trench-fill mudstones and turbidites and draping sediments. The structure of the accretionary wedge was presumably
formed owing to off-scraping and tectonic underplating. The off-scraped and tectonically underplated fragments were probably
tectonically juxtaposed along out-of-sequence thrusts with draping deposits. The radiolarian fauna was used to constrain the
ages of rocks and time of the accretion episodes in different parts of the accretionary wedge. The defined radiolarian assemblages
were correlated with the radiolarian scale for the Tethyan region using the method of unitary associations. In the Nabil zone,
the age of pelagic sediments is estimated to have lasted from the Late Jurassic to Early Cretaceous (Barremian); that of hemipelagic
sediments, from the early Aptian to middle Albian; and trench-fill and draping deposits of the accretionary complex date back
to the middle-late Albian. In the Rymnik zone, the respective ages of cherts, hemipelagic sediments, and trench facies with
draping deposits have been determined as Late Jurassic to Early Cretaceous (middle Albian), middle Aptian-middle Cenomanian,
and middle-late Cenomanian. East of the rear toward the frontal parts of the accretionary wedge, stratigraphic boundaries
between sediments of different lithology become successively younger. Timing of accretion episodes is based on the age of
trench-fill and draping sediments of the accretionary wedge. The accretion occurred in a period lasting from the terminal
Aptian to the middle Albian in the western part of the Nabil zone and in the middle Cenomanian in the eastern part of the
Rymnik zone. The western part of the Nabil zone accreted synchronously with the Kiselevka-Manoma accretionary wedge located
westerward on the continent. These accretionary wedges presumably formed along a single convergent plate margin, with the
Sakhalin accretionary system located to the south of the Kiselevka-Manoma terrane in the Albian. 相似文献
20.
Edoardo Barbero Luca Pandolfi Morteza Delavari Asghar Dolati Emilio Saccani Rita Catanzariti Valeria Luciani Marco Chiari Michele Marroni 《地学前缘(英文版)》2021,12(3):101106
The Durkan Complex is a key tectonic element of the Makran accretionary prism (SE Iran) and it has been interpreted as representing a continental margin succession. We present here a multidisciplinary study of the western Durkan Complex, which is based on new geological, stratigraphic, biostratigraphic data, as well as geochemical data of the volcanic and meta-volcanic rocks forming this complex. Our data show that this complex consists of distinct tectonic slices showing both non-metamorphic and very low-grade metamorphic deformed successions. Stratigraphic and biostratigraphic data allow us to recognize three types of successions. Type-I is composed by a Coniacian – early Campanian pelagic succession with intercalation of pillow lavas and minor volcaniclastic rocks. Type-II succession includes a volcanic sequence passing to a volcano-sedimentary sequence with Cenomanian pelagic limestones, followed by a hemipelagic sequence. This succession is characterized by abundant mass-transport deposits. Type-III succession includes volcanic and volcano-sedimentary sequences, which are stratigraphically covered by a Cenomanian platform succession. The latter is locally followed by a hemipelagic sequence. The volcanic rocks in the different successions show alkaline geochemical affinity, suggesting an origin from an oceanic within-plate setting. Our new results indicate that the western Durkan Complex represents fragments of seamounts tectonically incorporated in the Makran accretionary wedge during the latest Late Cretaceous–Paleocene. We propose that incorporation of seamounts in the frontal prism caused a shortening of the whole convergent margin and possibly contributed to controlling the deformation style in the Makran Accretionary Wedge during Late Cretaceous–Paleocene times. 相似文献