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1.
悉尼盆地位于澳大利亚东部,Lachlan褶皱带和New England褶皱带之间。悉尼盆地从晚石炭世末到中三叠世经历了弧后扩张到前陆盆地的不同阶段:弧后扩张阶段(石炭纪)、被动热沉降阶段(早、中二叠世Berry组)和挤压挠曲负载阶段(中二叠世Broughton组—三叠纪)。此时位于悉尼盆地东侧的New England褶皱带为岛弧背景。因此,二叠纪处于弧后盆地的南悉尼盆地受弧后扩张和东侧弧前海沟俯冲的影响地震活动强烈,发育一系列与地震有关的震积岩,形成多种类型的与地震活动有关的软沉积物变形构造。南悉尼盆地二叠系的软沉积物变形包括地裂缝、震褶层、液化脉、沙火山、负荷构造、火焰构造、枕状构造、球状构造、枕状层、滑塌构造、角砾岩化等。其中地裂缝、震褶层是地震颤动直接引起的断裂和褶皱;枕状层是地震颤动引起的砂层脱水、下沉形成的;液化脉、沙火山为液化的砂层穿入地震形成的裂隙形成的;负荷构造、火焰构造、枕状构造、球状构造是受地震颤动在砂、泥岩界面上由于砂层下沉、泥层上穿形成的;滑塌构造和角砾岩化是地震引起的重力滑塌或泥石流形成的。地裂缝、震褶层、液化脉、沙火山、负荷构造、火焰构造、枕状构造、球状构造、枕状层相当于原地震积岩,而滑塌构造和角砾岩化属于异地震积岩。 相似文献
2.
楚雄弧后前陆盆地的形成及演化 总被引：15，自引：2，他引：13
楚雄盆地的性质属弧后前陆盆地,盆地剖面结构由四个带组成：（１）岩浆弧;９２）褶皱逆冲带;（３）沉降带;（４）隆起带,盆地的形成演化受两期主要应力控制：早期受来自西南向的特提期洋沿哀牢山带的俯冲影响,形成凹陷盆地,时代为晚二叠世至晚三叠世,随后应力性质发生转变,沿哀牢山一带的主应力以剪切－抗日压为主,并派生东西向的扩张运动,形成断陷盆地。 相似文献
3.
西藏措勤中——新生代沉积盆地演化 总被引：2，自引：0，他引：2
措勤盆地位于西藏冈底斯地块中西段,是在古生界褶皱基底上发展起来的一个中一新生代盆地。通过对措勤盆地内发育的构造、地层、岩石及沉积相综合分析,讨论了措勤盆地与喜马拉雅构造带和班公-怒江构造带的对应演化关系,反演了措勤盆地的地质发展历史。其演化经历了盆地基底形成阶段（D—P）、复合弧后盆地演化阶段（J—E2）和高原隆升盆地消亡三个阶段（E2-现今）。 相似文献
4.
杨宗让 《沉积与特提斯地质》2002,22(3):53-59
地处柴南缘昆中蛇绿杂岩带与羌塘地块北缘可可西里—金沙江古缝合线之间的松潘—甘孜褶皱带(包括东昆仑构造带)，其主体应属古特提斯洋晚石炭世一晚三叠世时期向其北侧的柴达木古陆南缘俯冲过程中在活动陆缘弧—沟间隙之间增生形成的一个大型弧前构造带。具有由弧前盆地沉积楔和基底增生杂岩构成的双重结构特点，其形成与冈瓦纳大陆北缘若尔盖“三角”地块的楔入及俯冲带向南迁移有关。大致经历了晚石炭世一早三叠世狭窄弧前盆地和中晚三叠世宽阔弧前盆地两个主要演化阶段。 相似文献
5.
东北地区前中生代构造演化及其与晚中生代盆地发育的关系 总被引：6，自引：1，他引：5
摘 要 东北地区前中生代构造演化可大致分为如下阶段：（1） 中、新元古代阶段;（2） 早古
生代加里东阶段;（3） 泥盆纪—早石炭世早华力西阶段;（4） 晚石炭世—三叠纪晚华力西—印
支阶段。多旋回构造演化使该区形成由多期褶皱带和多中间或边缘地块组成的 “镶嵌构造
区”并为晚中生代大型含油气盆地的发育奠定了基础。 相似文献
6.
中亚造山带西南缘东天山觉罗塔格造山带广泛发育石炭纪火山岩，这些石炭纪火山岩的成因和构造历史一直是该区域地质问题争论的焦点.通过对东天山觉罗塔格造山带石炭纪基性火山岩详细的岩石学、地球化学、锆石U-Pb年代学和Sr-Nd同位素研究，获得了如下认识:（1）东天山觉罗塔格造山带石炭纪基性火山岩分为两期爆发，早期爆发时间为336 Ma，晚期爆发时间为320 Ma.早期336 Ma基性火山岩由玄武岩、玄武安山岩及同成分的火山碎屑岩组成，显示出弧火山岩属性；晚期320 Ma基性火山岩主要由玄武岩和玄武安山岩组成，包括Ⅰ型火山岩和Ⅱ型火山岩，Ⅰ型显示出大洋中脊玄武岩属性，Ⅱ型显示出弧玄武岩特征.（2）石炭纪基性火山岩中发现的大量捕获锆石（371~3 106 Ma）年龄谱系与中天山地块显示为相似的特征，表明它们在石炭纪之前可能同属一个板块，也指示早古生代地壳可能参与了成岩过程.（3）该区域石炭纪火山岩与现今存在的Okinawa Trough和Mariana Trough弧后盆地玄武岩（BABB）很相似，从弧玄武岩向洋中脊玄武岩的演变，反映了石炭纪中天山北部弧后盆地的发展.因此推断早石炭世火山岩为弧后盆地初始裂开阶段的产物，而晚石炭世火山岩为弧后盆地弧后扩张阶段的产物.早石炭世晚期的初始裂开和晚石炭世早期的弧后扩张表明天山洋的俯冲最终结束于晚石炭世末期，包括主大洋和弧后盆地最终关闭，而最终关闭的位置很可能位于中天山以南. 相似文献
7.
楚雄盆地处于中国云南省中部，位于扬子板块西南缘，南西界以红河断裂为界与哀牢山造山带相连，北西界为程海断裂，东边为绿汁江断裂。盆地基底包括结晶基底和褶皱基底双重结构。盆地内发育了中三叠世以后的沉积盖层，西部中三叠世和晚三叠世早、中期为海相沉积，晚期为海陆交互相和陆相沉积；盆地东部为陆相沉积。侏罗—白垩纪整个盆地为巨厚的陆相沉积。楚雄盆地的构造格架分为４个带：（１）哀牢山造山带；（２）褶皱逆冲带；（３）中部沉降带；（４）东部隆起带。盆地形成与演化分为六个阶段：（１）被动大陆边缘沉降阶段；（２）拉张热隆起边缘——裂谷盆地阶段；（３）沟－弧－盆系阶段；（４）残洋－周缘前陆盆地阶段；（５）走滑－拉张盆地阶段；（６）走滑－挤压－改造阶段。楚雄盆地的形成与演化体现了盆地动力学性质转化和复合，在多种动力系统作用下或经过多旋回构造阶段产生了复式盆地 相似文献
8.
右江三叠纪弧后盆地沉积特征及盆地演化 总被引：17，自引：0，他引：17
早二叠世后由干软防海槽褶皱成山及金沙江—哀牢山俯冲消减带的形成，使右江地区东部软防褶皱带前缘形成前陆盆地，广大西部滇黔桂地区形成弧后边缘海盆地．弧后盆地经历晚二叠世—早三叠世扩张裂陷，有较强火山活动，以基性熔岩流及安山质火山碎悄流沉积，具有初始洋壳化性质；中三叠世强烈蚴陷，以陆源碎屑浊流沉积为主，中三叠世末广大地区回返褶皱成山，盆地向西推移，晚三叠世形成狭窄的北东向萎缩坳陷盆地，卡尼期末充填隆起，盆地关闭。右江弧后盆地的关闭经历了突变式回返褶皱和渐变隆起上升两种不同的构造作用． 相似文献
9.
10.
西藏羌塘盆地的构造沉积特征及演化 总被引：11，自引：0，他引：11
西藏羌塘盆地是特提斯构造域内晚古生代—中生代海相复合盆地。经历了晚古生代板块构造演化阶段、中生代板块构造演化阶段和新生代抬升剥蚀阶段 ,形成了晚古生代大陆边缘盆地、中生代南羌塘被动大陆边缘和北羌塘弧后盆地以及晚侏罗世之后的构造地貌盆地。受多期构造运动作用 ,盆地从北向南形成了北缘冲褶带、北羌塘变形带、中央碰撞隆起带、南羌塘变形带和南缘冲断带五个构造单元。变形由坳陷边缘到中心逐渐减弱 ,侏罗山式褶皱样式 ,反映出盖层浅层滑脱的变形特征 相似文献
11.
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. 相似文献
12.
华南印支期碰撞造山--十万大山盆地构造和沉积学证据 总被引：27，自引：9，他引：18
十万大山盆地是云开造山带前陆地区的一个窄长的晚二叠世—中三叠世沉积盆地,位于扬子与华夏陆块拼接位置的西南端。十万大山盆地晚二叠世—中三叠世沉积由巨厚的磨拉石建造组成,并构成多个向上变粗和向上变细的构造-地层层序。云开造山带及前陆冲断带上泥盆统至下二叠统中发育了大量的印支期形成的薄皮褶皱和冲断构造。这些指示扬子和华夏陆块在印支期发生了强烈陆内碰撞与会聚及前陆盆地的沉积作用。P2 /P1 之间的不整合面是伸展构造向挤压构造转换的转换面,为华南印支期碰撞挤压造山或活化造山的序幕。T3 /T2 之间不整合面是挤压构造向伸展构造转换的转换面,是印支期活化挤压造山结束的界面,标志着晚二叠世开始的碰撞造山作用的结束。华南内部晚二叠世—中三叠世构造运动性质及转换与当时华南南缘存在的古特提斯洋的闭合及印支板块与华南陆块的碰撞作用有关。 相似文献
13.
The Late Permian–early Middle Triassic strata of the northern West Qinling area, northeastern Tibetan Plateau, are composed of sediment gravity flow deposits. Detailed sedimentary facies analysis indicates these strata were deposited in three successive deep-marine environments. The Late Permian–early Early Triassic strata of the Maomaolong Formation and the lowest part of the Longwuhe Formation define a NW–SE trending proximal slope environment. Facies of the Early Triassic strata composing the middle and upper Longwuhe Formation are consistent with deposition in a base-of-slope apron environment, whereas facies of the Middle Triassic Anisian age Gulangdi Formation are more closely associated with a base-of-slope fan depositional environment. The lithofacies and the spatial–temporal changes in paleocurrent data from these strata suggest the opening of a continental margin back-arc basin system during Late Permian to early Middle Triassic time in the northern West Qinling. U–Pb zircon ages for geochemically varied igneous rocks with diabasic through granitic compositions intruded into these deep-marine strata range from 250 to 234 Ma. These observations are consistent with extensional back-arc basin development and rifting between the Permian–Triassic Eastern Kunlun arc and North China block during the continent–continent collision and underthrusting of the South China block northward beneath the Qinling terrane of the North China block. Deep-marine sedimentation ended in the northern West Qinling by the Middle Triassic Ladinian age, but started in the southern West Qinling and Songpan-Ganzi to the south. We attribute these observations to southward directed rollback of Paleo-Tethys oceanic lithosphere, continued attenuation of the West Qinling on the upper plate, local post-rift isostatic compensation in the northern West Qinling area, and continued opening of a back-arc basin in the southern West Qinling and Songpan-Ganzi. Rollback and back-arc basin development during Late Permian to early Middle Triassic time in the West Qinling area explains: the truncated map pattern of the Eastern Kunlun arc, the age difference of deep-marine sediment gravity flow deposits between the Late Permian–early Middle Triassic northern West Qinling and the late Middle Triassic–Late Triassic southern West Qinling and Songpan-Ganzi, and the discontinuous trace of ophiolitic rocks associated with the Anyemaqen-Kunlun suture. 相似文献
14.
西南三江地区洋板块地层特征及构造演化 总被引：3，自引：3，他引：0
以大地构造研究为主导,初步梳理了三江地区洋板块地层系统的分布及其构造演化规律。本文阐述了三江地区经历原-古特提斯大洋连续演化、分阶段拼贴增生至最终俯冲消亡的地质演化历程。甘孜-理塘弧后洋盆于早石炭世打开,二叠纪—中三叠世进入顶峰扩张期,晚三叠世洋盆萎缩引起向西俯冲,最终在晚三叠世末局部地区保留残留海。哀牢山弧后洋盆不晚于早石炭世形成,早石炭世—早二叠世整体扩张发育,早二叠世末或晚二叠世初开始向西俯冲,晚三叠世最终完全关闭。金沙江洋盆早石炭世时已扩张成洋,到早二叠世晚期开始俯冲,石炭纪—早二叠世早期是金沙江洋盆扩张的主体时期,早二叠世晚期至早、中三叠世俯冲消亡。澜沧江弧后洋盆中晚泥盆世开始扩张,在石炭纪—早二叠世发育为成熟洋盆,早二叠世晚期洋内俯冲形成洋内弧,晚二叠世—早、中三叠世双向俯冲消亡。昌宁-孟连洋为特提斯洋主带,具有原-古特提斯洋连续演化的地质记录,晚奥陶世开始向东俯冲消减,二叠纪末、早三叠世发生弧-陆碰撞作用,昌宁-孟连洋盆闭合。 相似文献
15.
A. Van Heeswijck 《Australian Journal of Earth Sciences》2013,60(3):417-426
Upper Carboniferous to Lower Permian sedimentary rocks extend along the periphery of the northern Sydney Basin, a sub‐basin of the Sydney‐Gunnedah‐Bowen Basin complex. The basin contains basal basalts and volcanic sediments deposited in a nascent rift zone. This rift zone was created through crustal thinning during trench rollback on the eastern edge of the New England Orogen. Thermal subsidence created accommodation for predominantly marine Dalwood Group sediments. Clastic sedimentation then occurred in the Maitland‐Cessnock‐Greta Coalfield and Cranky Corner Basin during the Early Permian. This occurred on a broad shelf undergoing renewed thermal subsidence on the margin of a rift flank of the Tamworth Belt of the southern New England Orogen. Braidplain fans prograded or aggraded in two depositional sequences. The first sequence commences near the top of the Farley Formation and includes part of the Greta Coal Measures, while the second sequence includes the majority of the Greta Coal Measures and basal Branxton Formation. Thin, areally restricted mires formed during interludes in a high sedimentation regime in the lowstand systems tracts. As base‐level rose, areally extensive mires developed on the transgressive surface of both sequences. A paludal to estuarine facies changed to a shallow‐marine facies as the braidplain was transgressed. The transgressive systems tracts continued to develop with rising relative sea‐level. Renewed uplift in the hinterland resulted in the erosion of part of the transgressive systems tract and all of the highstand systems tract of the lower sequence. In the upper sequence a reduction in relative sea‐level rise saw the development of a deltaic to nearshore shelf highstand systems tract. Extensional dynamics caused a fall in relative base‐level and the development of a sequence boundary in the Branxton Formation. Finally, renewed thermal subsidence created accommodation for the overlying, predominantly marine Maitland Group. 相似文献
16.
C.G. Murray 《Ore Geology Reviews》1986,1(2-4)
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. 相似文献
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In a 60 Ma interval between the Late Carboniferous and the Late Permian, the magmatic arc associated with the cordilleran-type New England Fold Belt in northeast New South Wales shifted eastward and changed in trend from north–northwest to north. The eastern margin of the earlier (Devonian–Late Carboniferous) arc is marked by a sequence of calcalkaline lava flows, tuffs and coarse volcaniclastic sedimentary rocks preserved in the west of the Fold Belt. The younger arc (Late Permian–Triassic) is marked by I-type calcalkaline granitoids and comagmatic volcanic rocks emplaced mostly in the earlier forearc, but extending into the southern Sydney Basin, in the former backarc region. The growth of the younger arc was accompanied by widespread compressional deformation that stabilised the New England Fold Belt. During the transitional interval, two suites of S-type granitoids were emplaced, the Hillgrove Suite at about 305 Ma during an episode of compressive deformation and regional metamorphism, and the Bundarra Suite at about 280 Ma, during the later stages of an extensional episode. Isotopic and REE data indicate that both suites resulted from the partial melting of young silicic sedimentary rocks, probably part of the Carboniferous accretionary subduction complex, with heat supplied by the rise of asthenospheric material. Both mafic and silicic volcanic activity were widespread within and behind the Fold Belt from the onset of rifting (ca. 295 Ma) until the reestablishment of the arc. These volcanic rocks range in composition from MORB-like to calcalkaline and alkaline. The termination of the earlier arc, and the subsequent widespread and diverse igneous activity are considered to have resulted from the shallow breakoff of the downgoing plate, which allowed the rise of asthenosphere through a widening lithospheric gap. In this setting, division of the igneous rocks into pre-, syn-, and post-collisional groups is of limited value. 相似文献
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A.B. Cadle B. Cairncross A.D.M. Christie D.L. Roberts 《International Journal of Coal Geology》1993,23(1-4)
The coal-bearing sediments and coal seams of the Karoo Basin, Southern Africa are described and discussed. The Karoo Basin is bounded on its southern margin by the Cape Fold Belt, onlaps onto the Kaapvaal Craton in the north and is classified as a foreland basin. Coal seams are present within the Early Permian Vryheid Formation and the Triassic Molteno Formation.The peats of the Vryheid Formation accumulated within swamps in a cool temperate climatic regime. Lower and upper delta plain, back-barrier and fluvial environments were associated with peat formation. Thick, laterally extensive coal seams have preferentially accumulated in fluvial environments. The coals are in general inertinite-rich and high in ash. However, increasing vitrinite and decreasing ash contents within seams occur from west to east across the coalfields. The Triassic Molteno coal seams accumulated with aerially restricted swamps in fluvial environments. These Molteno coals are thin, laterally impersistent, vitrinite-rich and shaly, and formed under a warm temperate climatic regime.Palaeoclimate, depositional systems, differential subsidence and basin tectonics influence to varying degrees, the maceral content, thickness and lateral extent of coal seams. However, the geographic position of peat-forming swamps within a foreland basin, coupled with basin tectonics and differential subsidence are envisaged as the primary controls on coal parameters. The Permian coals are situated in proximal positions on the passive margin of the foreland basin. Here, subsidence was limited which enhanced oxidation of organic matter and hence the formation of inertinitic coals. The coals in this tectonic setting are thick and laterally extensive. The Triassci coals are situated within the tectonically active foreland basin margin. Rapid subsidence and sedimentation rates occurred during peat formation which resulted in the preservation of thin, laterally impersistent, high ash, vitrinite-rich, shaly coals. 相似文献
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The Malay Peninsula is characterised by three north–south belts, the Western, Central, and Eastern belts based on distinct differences in stratigraphy, structure, magmatism, geophysical signatures and geological evolution. The Western Belt forms part of the Sibumasu Terrane, derived from the NW Australian Gondwana margin in the late Early Permian. The Central and Eastern Belts represent the Sukhothai Arc constructed in the Late Carboniferous–Early Permian on the margin of the Indochina Block (derived from the Gondwana margin in the Early Devonian). This arc was then separated from Indochina by back-arc spreading in the Permian. The Bentong-Raub suture zone forms the boundary between the Sibumasu Terrane (Western Belt) and Sukhothai Arc (Central and Eastern Belts) and preserves remnants of the Devonian–Permian main Palaeo-Tethys ocean basin destroyed by subduction beneath the Indochina Block/Sukhothai Arc, which produced the Permian–Triassic andesitic volcanism and I-Type granitoids observed in the Central and Eastern Belts of the Malay Peninsula. The collision between Sibumasu and the Sukhothai Arc began in Early Triassic times and was completed by the Late Triassic. Triassic cherts, turbidites and conglomerates of the Semanggol “Formation” were deposited in a fore-deep basin constructed on the leading edge of Sibumasu and the uplifted accretionary complex. Collisional crustal thickening, coupled with slab break off and rising hot asthenosphere produced the Main Range Late Triassic-earliest Jurassic S-Type granitoids that intrude the Western Belt and Bentong-Raub suture zone. The Sukhothai back-arc basin opened in the Early Permian and collapsed and closed in the Middle–Late Triassic. Marine sedimentation ceased in the Late Triassic in the Malay Peninsula due to tectonic and isostatic uplift, and Jurassic–Cretaceous continental red beds form a cover sequence. A significant Late Cretaceous tectono-thermal event affected the Peninsula with major faulting, granitoid intrusion and re-setting of palaeomagnetic signatures. 相似文献