Metallogeny and tectonic development of the Tasman Fold Belt System in Queensland

The northern part of the Tasman Fold Belt System in Queensland comprises three segments, the Thomson, Hodgkinson- Broken River, and New England Fold Belts. The evolution of each fold belt can be traced through pre-cratonic (orogenic), transitional, and cratonic stages. The different timing of these stages within each fold belt indicates differing tectonic histories, although connecting links can be recognised between them from Late Devonian time onward. In general, orogenesis became younger from west to east towards the present continental margin. The most recent folding, confined to the New England Fold Belt, was of Early to mid-Cretaceous age. It is considered that this eastward migration of orogenic activity may reflect progressive continental accretion, although the total amount of accretion since the inception of the Tasman Fold Belt System in Cambrian time is uncertain.The Thomson Fold Belt is largely concealed beneath late Palaeozoic and Mesozoic intracratonic basin sediments. In addition, the age of the more highly deformed and metamorphosed rocks exposed in the northeast is unknown, being either Precambrian or early Palaeozoic. Therefore, the tectonic evolution of this fold belt must remain very speculative. In its early stages (Precambrian or early Palaeozoic), the Thomson Fold Belt was probably a rifted continental margin adjacent to the Early to Middle Proterozoic craton to the west and north. The presence of calc-alkaline volcanics of Late Cambrian Early Ordovician and Early-Middle Devonian age suggests that the fold belt evolved to a convergent Pacific-type continental margin. The tectonic setting of the pre-cratonic (orogenic) stage of the Hodgkinson—Broken River Fold Belt is also uncertain. Most of this fold belt consists of strongly deformed, flysch-type sediments of Silurian-Devonian age. Forearc, back-arc and rifted margin settings have all been proposed for these deposits. The transitional stage of the Hodgkinson—Broken River Fold Belt was characterised by eruption of extensive silicic continental volcanics, mainly ignimbrites, and intrusion of comagmatic granitoids in Late Carboniferous Early Permian time. An Andean-type continental margin model, with calc-alkaline volcanics erupted above a west-dipping subduction zone, has been suggested for this period. The tectonic history of the New England Fold Belt is believed to be relatively well understood. It was the site of extensive and repeated eruption of calc-alkaline volcanics from Late Silurian to Early Cretaceous time. The oldest rocks may have formed in a volcanic island arc. From the Late Devonian, the fold belt was a convergent continental margin above a west-dipping subduction zone. For Late Devonian- Early Carboniferous time, parallel belts representing continental margin volcanic arc, forearc basin, and subduction complex can be recognised.A great variety of mineral deposits, ranging in age from Late Cambrian-Early Ordovician and possibly even Precambrian to Early Cretaceous, is present in the exposed rocks of the Tasman Fold Belt System in Queensland. Volcanogenic massive sulphides and slate belt-type gold-bearing quartz veins are the most important deposits formed in the pre-cratonic (orogenic) stage of all three fold belts. The voicanogenic massive sulphides include classic Kuroko-type orebodies associated with silicic volcanics, such as those at Thalanga (Late Cambrian-Early Ordovician. Thomson Fold Belt) and at Mount Chalmers (Early Permian New England Fold Belt), and Kieslager or Besshi-type deposits related to submarine mafic volcanics, such as Peak Downs (Precambrian or early Palaeozoic, Thomson Fold Belt) and Dianne. OK and Mount Molloy (Silurian—Devonian, Hodgkinson Broken River Fold Belt). The major gold—copper orebody at Mount Morgan (Middle Devonian, New England Fold Belt), is considered to be of volcanic or subvolcanic origin, but is not a typical volcanogenic massive sulphide.The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusives of the transitional tectonic stage of the three fold belts, particularly the Late Carboniferous Early Perman of the Hodgkinson—Broken River Fold Belt and the Late Permian—Middle Triassic of the southeast Queensland part of the New England Fold Belt. In general, these deposits are small but rich. They include tin, tungsten, molybdenum and bismuth in granites and adjacent metasediments, base metals in contact meta somatic skarns, gold in volcanic breccia pipes, gold-bearing quartz veins within granitoid intrusives and in volcanic contact rocks, and low-grade disseminated porphyry-type copper and molybdenum deposits. The porphyry-type deposits occur in distinct belts related to intrusives of different ages: Devonian (Thomson Fold Belt), Late Carboniferous—Early Permian (Hodgkinson—Broken River Fold Belt). Late Permian Middle Triassic (southeast Queensland part of the New England Fold Belt), and Early Cretaceous (northern New England Fold Belt). All are too low grade to be of economic importance at present.Tertiary deep weathering events were responsible for the formation of lateritic nickel deposits on ultramafics and surficial manganese concentrations from disseminated mineralisation in cherts and jaspers.     

Metallogeny and tectonic development of the Tasman Fold Belt System in Victoria

Current evidence suggests that most of Victoria is underlain by a relatively thick (20 km +) basement of sialic composition of assumed Proterozoic age. This basement is nowhere exposed and its structural relationship with exposed Palaeozoic rocks is conjectural. This uncertainty has resulted in both ensimatic and ensialic tectonic models being proposed for Victoria during the Cambrian.Mineralization associated with Cambrian igneous activity shows a variety of styles from minor orthomagmatic chromite deposits, through Au and Cu deposits of syngenetic or epigenetic origin, to Fe---Mn, Ba occurrences of exhalative volcanogenic affiliation.Cambrian volcanism and associated sedimentation was followed by the deposition of dominantly quartz-rich turbidites with interbedded shale and siliceous units. Subsequent to the epi-Ordovician Benambran Orogeny, late Silurian crustal extension caused several rifts to open along roughly orthogonal NW and NE aligned fractures. Within these fault-bounded depressions, thick acid volcanic sequences were deposited in close association with shallow-marine sediments. Mineralization in these Upper Silurian rocks comprises polymetallic base-metal sulphide lenses and minor disseminations, at least some of which are of exhalative volcanogenic affiliation.The Silurian rifts were obliterated and their rocks strongly deformed during the Bindian (Bowning) deformation during late Silurian to early Devonian time. This in turn was followed by another episode of crustal extension and rifting, during which the formation of a broad meridional trough marks the Buchan Rift. A very thick sequence of largely subaerial bimodal volcanics is overlain by shelf limestone and mudstone. A variety of minor base metal, barite, manganese, and iron mineralization is hosted by these volcanics and shelf sediments.The mid-Devonian Tabberabberan Orogeny was followed in the Late Devonian by bimodal volcanism and granite intrusion, and “red-bed”-type non-marine sedimentation. In Central Victoria, thick bimodal volcanics were erupted into a series of cauldron subsidences and intruded by comagmatic granites. Bimodal volcanism also occurred in the Mount Howitt Province farther east, but was followed by deposition of extensive fluviatile and lacustrine sediments (mainly mudstone, sandstone, and minor conglomerate). In the Mansfield Basin, these contain minor sedimentary copper occurrences.There are four distinct episodes of granite emplacement in Victoria, namely Late Cambrian -Early Ordovician (Delamerian) in the Glenelg Zone; Early Silurian (Benambran) in the Highlands Zone; Early Devonian (Bindian) in the Grampians, Ararat-Bendigo, Highlands, and Mallacoota Zones; and Middle Devonian-Carboniferous (post Tabberabberan) in the Ararat- Bendigo, Melbourne, Howqua, and Highlands Zones. Data for the Delamerian granitoids are sketchy, but in the remaining groups S-type granitoids predominate with the exception of eastern Victoria, east of the Yalmy Fault (I-S line), where only I- and A-type granitoids occur. A variety of Sn, Mo, W deposits and prospects are associated with the Benambran and younger intrusive phases.Victoria is a major gold province which has produced nearly 2.5 × 10⁶ kg gold. Primary gold occurs in a number of geological settings including veins and disseminations spatially associated with mafic Cambrian volcanism, vein deposits in turbiditic sequences of central and eastern Victoria, veins associated with mafic and intermediate intrusives of Mid to Late Devonian age, and minor amounts associated with a variety of granitoids and porphyry dykes.     

辽吉朝褶皱带古元古宙岩浆核杂岩及其大地构造意义

通过对辽吉朝古元古代褶皱带的构造演化分析,尤其对褶皱带南带内发育的典型构造组合及相应出现的岩浆活动、变质作用和为形作用的系统构造分析,提出岩浆核杂岩是古元古代褶皱带早期演化过程中形成的主要构造型式。岩浆核杂岩主要由3种成分、性质、特点及变质演化不同的构造单元构成,即核部岩浆杂岩、外部的滑覆体壳有其间的幔部顺层韧性剪切带。岩浆核杂岩的构造分析,揭示出它们形成于褶皱带早期阶段演化的伸展作用过程中。     

辽吉朝褶皱带古元古宙岩浆核杂岩及其大地构造意义

通过对辽吉朝古元古代褶皱带的构造演化分析,尤其对褶皱带南带内发育的典型构造组合及相应出现的岩浆活动、变质作用和变形作用的系统构造分析,提出岩浆核杂岩是古元古代褶皱带早期演化过程中形成的主要构造型式。岩浆核杂岩主要由3种成分、性质、特点及变质演化不同的构造单元构成,即核部岩浆杂岩、外部的滑覆体壳及其间的幔部顺层韧性剪切带。岩浆核杂岩的构造分析,揭示出它们形成于褶皱带早期阶段演化的伸展作用过程中。     

Metallogeny and tectonic development of the Tasman Fold Belt System in New South Wales

The northwestern corner of New South Wales consists of the paratectonic Late Proterozoic to Early Cambrian Adelaide Fold Belt and older rocks, which represent basement inliers in this fold belt. The rest of the state is built by the composite Late Proterozoic to Triassic Tasman Fold Belt System or Tasmanides.In New South Wales the Tasman Fold Belt System includes three fold belts: (1) the Late Proterozoic to Early Palaeozoic Kanmantoo Fold Belt; (2) the Early to Middle Palaeozoic Lachlan Fold Belt; and (3) the Early Palaeozoic to Triassic New England Fold Belt. The Late Palaeozoic to Triassic Sydney—Bowen Basin represents the foredeep of the New England Fold Belt.The Tasmanides developed in an active plate margin setting through the interaction of East Gondwanaland with the Ur-(Precambrian) and Palaeo-Pacific plates. The Tasmanides are characterized by a polyphase terrane accretion history: during the Late Proterozoic to Triassic the Tasmanides experienced three major episodes of terrane dispersal (Late Proterozoic—Cambrian, Silurian—Devonian, and Late Carboniferous—Permian) and six terrane accretionary events (Cambrian—Ordovician, Late Ordovician—Early Silurian, Middle Devonian, Carboniferous, Middle-Late Permian, and Triassic). The individual fold belts resulted from one or more accretionary events.The Kanmantoo Fold Belt has a very restricted range of mineralization and is characterized by stratabound copper deposits, whereas the Lachlan and New England Fold Belts have a great variety of metallogenic environments associated with both accretionary and dispersive tectonic episodes.The earliest deposits in the Lachlan Fold Belt are stratabound Cu and Mn deposits of Cambro-Ordovician age. In the Ordovician Cu deposits were formed in a volcanic are. In the Silurian porphyry Cu---Au deposits were formed during the late stages of development of the same volcanic are. Post-accretionary porphyry Cu---Au deposits were emplaced in the Early Devonian on the sites of the accreted volcanic arc. In the Middle to Late Silurian and Early Devonian a large number of base metal deposits originated as a result of rifting and felsic volcanism. In the Silurian and Early Devonian numerous Sn---W, Mo and base metal—Au granitoid related deposits were formed. A younger group of Mo---W and Sn deposits resulted from Early—Middle Carboniferous granitic plutonism in the eastern part of the Lachlan Fold Belt. In the Middle Devonian epithermal Au was associated with rifting and bimodal volcanism in the extreme eastern part of the Lachlan Fold Belt.In the New England Fold Belt pre-accretionary deposits comprise stratabound Cu and Mn deposits (pre-Early Devonian): stratabound Cu and Mn and ?exhalite Au deposits (Late Devonian to Early Carboniferous); and stratabound Cu, exhalite Au, and quartz—magnetite (?Late Carboniferous). S-type magmatism in the Late Carboniferous—Early Permian was responsible for vein Sn and possibly Au---As---Ag---Sb deposits. Volcanogenic base metals, when compared with the Lachlan Fold Belt, are only poorly represented, and were formed in the Early Permian. The metallogenesis of the New England Fold Belt is dominated by granitoid-related mineralization of Middle Permian to Triassic age, including Sn---W, Mo---W, and Au---Ag---As Sb deposits. Also in the Middle Permian epithermal Au---Ag mineralization was developed. During the above period of post-orogenic magmatism sizeable metahydrothermal Sb---Au(---W) and Au deposits were emplaced in major fracture and shear zones in central and eastern New England. The occurrence of antimony provides an additional distinguishing factor between the New England and Lachlan Fold Belts. In the New England Fold Belt antimony deposits are abundant whereas they are rare in the Lachlan Fold Belt. This may suggest fundamental crustal differences.     

Orogen-transverse tectonic window in the Eastern Himalayan fold belt: A superposed buckling model

The Eastern Lesser Himalayan fold-thrust belt is punctuated by a row of orogen-transverse domal tectonic windows. To evaluate their origin, a variety of thrust-stack models have been proposed, assuming that the crustal shortening occurred dominantly by brittle deformations. However, the Rangit Window (RW) in the Darjeeling-Sikkim Himalaya (DSH) shows unequivocal structural imprints of ductile deformations of multiple episodes. Based on new structural maps, coupled with outcrop-scale field observations, we recognize at least four major episodes of folding in the litho-tectonic units of DSH. The last episode has produced regionally orogen-transverse upright folds (F₄), the interference of which with the third-generation (F₃) orogen-parallel folds has shaped the large-scale structural patterns in DSH. We propose a new genetic model for the RW, invoking the mechanics of superposed buckling in the mechanically stratified litho-tectonic systems. We substantiate this superposed buckling model with results obtained from analogue experiments. The model explains contrasting F₃–F₄ interferences in the Lesser Himalayan Sequence (LHS). The lower-order (terrain-scale) folds have undergone superposed buckling in Mode 1, producing large-scale domes and basins, whereas the RW occurs as a relatively higher-order dome nested in the first-order Tista Dome. The Gondwana and the Proterozoic rocks within the RW underwent superposed buckling in Modes 3 and 4, leading to Type 2 fold interferences, as evident from their structural patterns.     

Tok-Algoma magmatic complex of the Selenga-Stanovoi Superterrain in the Central Asian fold belt: Age and tectonic setting

According to the results of U-Pb geochronological investigations, the hornblende subalkali diorite rocks making up the Tok-Algoma Complex in the eastern part of the Selenga-Stanovoi Superterrain of the Central Asian fold belt were formed in the Middle Jurassic rather than in the Middle Archean as was suggested previously. Thus, the age of the regional amphibolite facies metamorphism manifested itself in the Ust??-Gilyui rock sequence of the Stanovoi Complex and that superimposed on granitoids of the Tok-Algoma Complex is Mesozoic rather than Early Precambrian. The geochemical features of the Tok-Algoma granitoids are indicative of the fact that they were formed in the geodynamic setting of the active continental margin or a mature island arc. Hence, it is possible to suggest that the subduction processes along the southern boundary between the Selenga-Stanovoi Superterrain and the Mongolian-Okhotsk ocean basin in the Middle Jurassic resulted in the formation of a magmatic belt of over 500 km in length.     

Scandinavian Caledonide Metallogeny in a plate tectonic perspective

Caledonian metallogeny has endowed Scandinavia with abundant metalliferous mineral resources of several genetical and compositional types, many of which have been exploited at various scales from the seventeenth century onwards. Because of this long history of exploration/exploitation, coupled with excellent exposures, the Caledonian orogen in Scandinavia can be taken as a model to illustrate the relationship between metallogenic evolution and plate tectonics. Its orogenic and metallogenic development can be related to a period of plate movements which started about 700–600?Ma ago with rifting and break-up of a Proterozoic megacontinent (Rodinia) followed by the opening-up of a wide ocean (Iapetus), and ending with collision between the Laurentian and Baltic continents (the climactic Scandian phase of orogeny) in Silurian times. Fragments of this sedimentary, magmatic and tectonic history are recorded in various autochthonous, and allochthonous units which were ultimately thrusted eastwards above the Baltic plate margin. The present consensus is that sequences deposited on the margin of the Laurentian plate are represented in the Uppermost Allochthon (UmA) mostly in northern Norway. The Neoproterozoic and Cambrian history of this margin started with the rifting of Rodinia, followed by the development of an Atlantic-type margin which was characterised by an easterly thickening, continental, shelf-wedge of basal quartz sandstones and an overlying blanket of thick carbonate banks reflecting the drift of Laurentia towards equatorial paleo-latitudes. This setting is considered to have been host to two characteristic types of stratabound-stratiform ores: massive to disseminated Zn-Pb-Cu and Cu-Zn sulphides in sedimentary and mixed sedimentary-volcanic lithologies with original ore reserves up to 5–6?Mt (Bleikvassli, Mofjellet); and numerous, laterally extensive, magnetite-hematite deposits in marble-metapelite lithologies. The economically most important of the latter group are the deposits of the Dunderlandsdal area where resources of around 500?Mt were present. Early rift basins preserved on the Baltic side of the rifted megacontinent, were filled with coarse clastites prior to establishment of a passive plate margin in Cambrian times. The passive margin was characterised by shallow marine sandstones and later bituminous Alum Shales deposited in a stable, epicontinental sea. Platform sedimentation was accompanied by local magmatic activity of rift-type tholeiitic through to carbonatitic compositions. This plate margin is presently represented in autochthonous and allochthonous sequences in the lower parts of the Caledonian nappe pile. Metalliferous mineral formation related to this time and setting was of limited importance and comprised previously worked Nb, P and Fe ores in carbonatites of the Fen Complex, vast but uneconomic resources of U, Mo, Ni and V in the Alum Shales, and minor stratabound base metal sulphides and orthomagmatic Cr and Ni-Cu-(PGE) occurrences. Continental margin and oceanic successions, probably developed along the edge of a microcontinent within the Iapetus ocean, are represented in the Gula, Støren and equivalent, sequences in the Upper Allochthon (UA), tectonostratigraphically above and west of the Baltic platform lithologies. These host many Cu-Zn sulphide ores intimately related to tholeiitic basalt units in sedimentary sequences dominated by pelitic and psammitic material, as well as bituminous shales and quartzites of possible ribbon-chert origin. Original ore reserves around 20?Mt were known at the now abandoned Tverrfjell mine and the recently closed Joma deposit. Minor Cu-Ni ores occur in subvolcanic, mafic-ultramafic intrusions. Major plate convergence is first recorded in the Middle to Late Cambrian (about 505?Ma), when subduction along the outer margin of Baltica affected rocks which are now found in or below the basal parts of the UA. The metallogenic significance of this subduction is uncertain; related magmatic and ore-forming processes have yet to be documented. The earliest subduction-related sequences of major ore-forming importance, however, are slightly younger (Early Ordovician) and are presently found in the UA and partly in the UmA. One of these is the Stekenjokk-Fundsjø arc sequence (about 490?Ma) which forms a central unit in the mountain chain, comprising bimodal, immature arc-type volcanites and high-level felsic intrusions. The sequence formed in a primary oceanic setting outboard of the Baltica plate while this lay in an approximately east-west position opposite to, and at some distance from, the Siberian plate, and was amalgamated with the Gula Complex in Ordovician times. Abundant VMS deposits are associated with thick, often graphitic, tuffites and are of the Zn-Cu type with generally high Zn/Cu ratios. The biggest known deposit (Stekenjokk-Levi) contained 26?Mt of ore, four others had individual tonnages of about 3?Mt and have been important base metal producers. Another series of arc sequences are found at higher levels in the nappe pile, in southwestern Norway, the western Trondheim Region, the western Grong District, Leka and Lyngen. Mafic or bimodal volcanic and plutonic lithologies comprise many types characteristic of immature arcs and often include ophiolitic successions. They all formed in oceanic arc-marginal basin systems on the Laurentian side of the Iapetus ocean between 500 and 480?Ma. VMS deposits of the Cu-Zn type are abundant and several of these were important base metal producers in the past. The biggest deposit is Løkken which contained 30?Mt of ore; six fall in the 1–10?Mt class and include the Skorovas and other deposits in the western Grong District and in southwest Norway. Orthomagmatic ores occur in the form of PGE mineralisation in ultramafic cumulates in the basal parts of ophiolite successions and Cu-Ni-PGE mineralisation related to high-level intrusions of boninitic affinity; none of these have hitherto been of economic significance. The immature arc-marginal basin systems near Laurentia continued to evolve and in Early to Middle Ordovician times magmatism gradually changed to predominantly calc-alkaline igneous activity characteristic of an active continental margin. Major VMS ores seem to be scarce in these sequences which are most extensively developed in central and southwest Norway. Known metalliferous deposits are predominantly iron-formations ranging from magnetite- to pyrite-dominated types with varying base-metal contents; Zn-Pb-Cu mineralisation is subordinate. Major granodioritic plutons which intruded the mature-arc sequences at an advanced stage of development (c.460?Ma) occasionally contain vein- and stockwork-type Cu-Mo mineralisation, so far with no economic significance. By the end of the Ordovician, convergence of the Laurentian and Baltic continents had resulted in considerable narrowing of the Iapetus ocean and obduction of the arc/arc-basin systems on to the edge of the Laurentian plate. Material derived from the uplifted sequences supplied detritus to the remaining, narrow, basin. At about the Ordovician/Silurian boundary these thick clastic, often calcareous, sequences and their crustal substrata were intruded by rift-type, mainly tholeiitic to alkaline magmas and minor subduction-related melts; local volcanism also accompanied this activity. This important magmatic event is interpreted to reflect a paleotectonic setting characterised by transcurrent movements and development of local transtensional regimes and fault-controlled sedimentary basins during the initial, oblique, interference of the Baltic and Laurentian plate margins. Its metallogenic manifestation is seen partly in occasional Ni-Cu deposits in mafic intrusions, including the Bruvann, Råna, deposit presently being exploited. More abundant, however, are stratabound sulphides which are associated with the volcanic rocks, or hosted in the sedimentary successions often closely related to mafic intrusions. The most important past-producers were found in the Røros and Sulitjelma districts, and included several individual deposits ranging from 1 up to nearly 9?Mt in size and dominated by Cu and Zn in highly variable proportions and grades. Partly overlapping in time with the rift-related magmatism, an array of large, mafic to granitic batholiths was emplaced in rock sequences which are presently found in the Uppermost and Upper Allochthons. This activity continued through the Late Ordovician and Early Silurian, presumably along the Laurentian plate margin in response to westward subduction of the edge of Baltica. Its metallogenic significance is limited to small and uneconomic skarn-, pegmatite- and quartz-vein mineralisation of Zn-Pb-Cu, Mo, W and Be. The ultimate collision between Laurentia and Baltica occurred during the Silurian, when the accretionary prism with granitic batholiths was obducted onto the Baltic margin. The obduction and subsequent uplift of the subducted edge of Baltica led to the formation of intramontane ORS basins in the Early and Middle Devonian. The Caledonian orogeny terminated with the deformation of the ORS basins in the Late Devonian. The collisional stage is metallogenically represented by three types of deposits, i.e. lead sandstone deposits (Pb, Zn, Ba, F and Cu), carbonate-hosted base-metal deposits, and vein deposits with variable proportions of Au, Ag, Pb, Cu, Zn, Fe, As, Sb, W, Mo and/or U. The first type, which comprises deposits with up to 5.0?Mt lead metal (Laisvall) is by far the most important economically. The vein deposits have in the past been the site for small-scale mining of precious metals and molybdenite. Although the exact timing of the different ore-forming events is poorly constrained, all types seem related to a continuous process of tectonically induced fluid flow during episodes of crustal shortening and uplift. Brief comparisons with other parts of the now-rifted Caledonian-Appalachian orogen reveal both similarities and differences in the relative importance of the ore types generated during the time span covered in the present account.     

贺兰山构造带构造—地层层序及构造演化

贺兰山构造带及邻区形成演化经历有多期叠加改造和多个伸展—聚敛旋回构造运动,形成了区域内多套构造—地层层序,因此,开展贺兰山构造带构造—地层层序及构造演化研究对深入理解其地质结构和油气勘探有着重要的意义。本文旨在综合利用野外调查、地震数据和1：50 000区域地质资料,采用野外实地调查和地震剖面精细解析相结合的方法对研究区区域不整合面的分布特征和规律进行详尽分析研究,根据区域不整合面的发育特征,建立区域地层年代格架,划分构造—地层层序,进而对盆地演化阶段进行探讨。研究表明,研究区自下至上发育Pt₂Ch-Jx/Pt₁、∈₁/An∈、C₂/O、T/P、J_1-2/An J、K₁/An K₁、E₃q—N/AnE,据此将研究区垂向上划为7个构造—地层层序：基底构造层、中元古界构造层、震旦系—奥陶系构造层、石炭系—三叠系构造层、侏罗系构造层、下白垩统构造层、新生界构造层。贺兰山构造带构造演化经历中新元古代—早古生代陆缘盆地坳陷—裂谷演化阶段;晚古生代—中三叠世陆相盆地坳陷沉积阶段;晚三叠世局部伸展;中侏罗世—早白垩世大规模逆冲推覆阶段,普遍发育多条大型北东向逆冲断裂;始新世开始进入盆—岭构造形成阶段。     

贺兰山构造带构造—地层层序及构造演化

贺兰山构造带及邻区形成演化经历有多期叠加改造和多个伸展—聚敛旋回构造运动,形成了区域内多套构造—地层层序,因此,开展贺兰山构造带构造—地层层序及构造演化研究对深入理解其地质结构和油气勘探有着重要的意义。本文旨在综合利用野外调查、地震数据和1：50 000区域地质资料,采用野外实地调查和地震剖面精细解析相结合的方法对研究区区域不整合面的分布特征和规律进行详尽分析研究,根据区域不整合面的发育特征,建立区域地层年代格架,划分构造—地层层序,进而对盆地演化阶段进行探讨。研究表明,研究区自下至上发育Pt2Ch-Jx/Pt1、∈1/An ∈、C2/O、T/P、J1-2/An J、K1/An K1、E3q—N/AnE,据此将研究区垂向上划为7个构造—地层层序：基底构造层、中元古界构造层、震旦系—奥陶系构造层、石炭系—三叠系构造层、侏罗系构造层、下白垩统构造层、新生界构造层。贺兰山构造带构造演化经历中新元古代—早古生代陆缘盆地坳陷—裂谷演化阶段;晚古生代—中三叠世陆相盆地坳陷沉积阶段;晚三叠世局部伸展;中侏罗世—早白垩世大规模逆冲推覆阶段,普遍发育多条大型北东向逆冲断裂;始新世开始进入盆—岭构造形成阶段。     

Basement-cover relations in the Appalachian fold and thrust belt

The external massifs along the Appalachian orogen include Precambrian basement rocks with attached cover. To the northwest (cratonward), in the Appalachian foreland fold and thrust belt, Palaeozoic sedimentary rocks, but no basement rocks, are exposed; that belt was the subject of the classic debate about thin-skinned (deformed cover rocks detached from undeformed basement) and thick-skinned (basement deformed with attached cover) structural styles. Presently available data indicate detached cover rocks and thin-skinned style in the fold and thrust belt: large-scale thrusting occurred late in the orogenic history. In the external basement massifs, late Precambrian graben-fill sedimentary and volcanic rocks indicate early basement faults; and within the craton, steep basement faults bound graben blocks of Cambrian age. Distribution of known basement faults suggests that basement rocks beneath the fold and thrust belt may also be faulted. Local episodic synsedimentary structural movement through much of the Palaeozoic is documented by stratigraphy in the fold and thrust belt. Axes of early synsedimentary structures are approximately coincident with axes of late folds and thrust fault ramps, but stratigraphic data show that magnitude of the early structures was much less than that of the late structures. These relations suggest the interpretation that early low-magnitude structures formed in cover rocks over basement faults and that the early structures, or the basement faults, significantly influenced the geometry of later detachment structures during large-scale horizontal translation.     

东天山古生代斑岩铜矿床成矿规律和构造背景

东天山铜成矿带是中亚成矿域的重要组成部分, 发育土屋、延东大型铜矿, 三岔口、玉海中型铜矿, 赤湖、福兴、灵龙、玉带和四顶黑山等小型铜矿床。其中的斑岩铜矿带主要沿大南湖-头苏泉岛弧带近东西向展布, 其成岩作用集中于志留纪和石炭纪, 而成矿峰期为石炭纪。东天山斑岩铜矿带赋矿围岩包括火山岩、花岗岩和沉积岩, 围岩蚀变主要有黑云母-磁铁矿化、绢英岩化和青磐岩化, 钾化相对较弱。成矿岩体主要为中酸性钙碱性花岗岩, 富集大离子亲石元素, 亏损高场强元素, 具有高Sr/Y比值, 显示典型的岛弧岩浆岩和埃达克质特征。成矿流体早阶段发育大量含子晶的高盐度包裹体, 为H₂O-NaCl±CO₂体系, 氢氧硫同位素显示明显的岩浆热液特征。锶钕铪同位素表明成矿岩体具有新生地壳和亏损地幔混合来源。东天山斑岩铜矿带形成于古天山洋的多期次俯冲造山, 因而具有多期叠加成矿的特征。石炭纪钙碱性岩浆岩是下一步找矿的主要目标, 后期构造叠加可能导致富矿体的形成。

     

Style and timing of tectonic deformation across the Bou Arada-El Fahs troughs system,Northeast Tunisia: integration in the structural evolution of Atlas fold and thrust belt

The Bou Arada-El Fahs troughs system is a particularly E-W trending collapsed structure with the manifestation of normal-to-strike-slip faults. A combined multi-source and multi-scalar structural and geophysical investigation provides important insights on the geometry and the kinematics evolution of trough systems in the Atlas of Tunisia. New data, as well as a reappraisal of available data show that the studied troughs system is established during three main successive events: the Oligocene-Miocene, the Tortonian, and the Plio-Quaternary events. The goal of this paper is to present the structural evolution of the study area, on a pre-structured substratum. The structural evolution progressed from an extensional event, manifested by the formation of grabens, passing by an episode of reactivation of faults related troughs in strike-slip motion during the Atlas compression accompanied by an en-échelon folding in foot wall and hanging wall. These results acquired and presented in the following order: We will initially present the geological context by integrating and correlating the lithostratigraphic data. We continue by examining the geometry and kinematics of structure-related troughs via the detailed geological mapping, the interpretation of available 2D seismic data, and the interpretation of processed fault slip data. This integrated geological and geophysical study allows a better understanding of the BETS, and makes it possible to propose a new geometrical and kinetic model of the establishment of trough structure in the Tunisian Atlas.     

扎格罗斯褶皱冲断带构造变形特征

扎格罗斯褶皱冲断带是扎格罗斯碰撞造山带的前陆褶皱冲断带, 也是波斯湾周缘前陆盆地的楔顶带, 自北东到南西垂直于构造线方向可分为高扎格罗斯冲断带和扎格罗斯简单褶皱带, 自北西到南东沿构造线方向可分为洛雷斯坦区(Lorestan)、迪兹富勒湾区(Dezful Embayment)和法尔斯区(Fars)。扎格罗斯褶皱冲断带的形成始于晚白垩世阿拉伯板块的洋壳向北俯冲到欧亚板块之下, 褶皱冲断构造从北东部缝合带向南西方向伸展, 并在上新世基本定型。本文选取了横切扎格罗斯褶皱冲断带的3条地质剖面和两条局部地震剖面进行构造变形分析。剖面分析显示研究区垂向上由一条大滑脱面将扎格罗斯褶皱冲断带剖面分为上、下两个构造层, 褶皱冲断变形从北东到南西向由强变弱。研究区发育走滑、挤压和拉张3种构造变形, 挤压构造变形占主导地位。挤压构造变形又包括滑脱褶皱、断展褶皱、断弯褶皱和双重构造等。     

川东南褶皱带洞岩铅锌矿床闪锌矿Rb-Sr同位素测年及其构造变形时代

重庆西阳县洞岩铅锌矿床位于川东南褶皱带中,为一中低温热液铅锌矿床,预测Zn金属量10.14万t。矿(化)体主要沿NNE向、NWW向断层呈脉状分布,或沿层间破碎带呈似层状分布。赋矿围岩为奥陶系碳酸盐岩。川东南褶皱带中这一类型铅锌矿床的形成时代以及与NNE向断层相互关系研究薄弱。本文运用闪锌矿Rb-Sr同位素测年方法,测得洞岩铅锌矿床成矿年龄为(157.7±3.3) Ma,表明该矿床的主成矿阶段年龄为晚侏罗世。闪锌矿(87Sr/86Sr)i值为0.71347,远高于早期及同期沉积碳酸盐比值,可能与大气淡水加入有关。川东南褶皱带为推覆-滑脱的薄皮构造,褶皱变形的主要时期为中晚侏罗世的燕山运动早期。洞岩闪锌矿的Rb-Sr等线年龄与上述构造变形时代一致,说明矿床的形成与早燕山构造变形事件有关。