共查询到20条相似文献，搜索用时 484 毫秒
1.
A regional magnetic survey was carried out over an area of 8000 km2 in Godavari districts of Andhra Pradesh, India, which is covered by the rocks of Eastern Ghat Mobile Belt (EGMB)viz., the Khondalitic series and Charnockites in the northern half and Permian to Mesozoic and Cenozoic sediments in the southern
half, and forms a part of the Krishna-Godavari (K-G) basin. The survey brought out a strong NE-SW trending anomaly in the
area covered by the rocks of Eastern Ghat Mobile Belt (EGMB), and a mild ENE-WSW trending anomaly in the area covered by the
sediments of the Krishna-Godavari (K-G) basin. The NE-SW trending anomaly in the northern half could be attributed to the
exposed/near surface Charnockite basement that has come closer to the surface as a result of Eastern Ghat Mobile Belt (EGMB)
tectonics. Explanation of the mild ENE-WSW trending anomaly over the sediments of the Krishna-Godavari (K-G) basin required
a faulted magnetic basement at depth downthrown towards the south. It is therefore concluded that the Charnockitic basement
together with the Khondalite group of rocks which are folded and faulted during the different phases of tectonics of Eastern
Ghat Mobile Belt (EGMB) extend into the Krishna-Godavari (K-G) basin and further, were involved in faulting during the phases
of formation and sedimentation in the Krishna-Godavari (K-G) basin. 相似文献
2.
Regional mapping of a section across the Eastern Ghats Mobile Belt (EGMB) north of the Godavari graben in Eastern Peninsular India by using Landsat Thematic Mapper data enables recognition of a number of shear zones, lineaments, and structural domes and basins. A conspicuous megashear occurs at the western boundary of the granulite facies rocks of the EGMB adjacent to the Archean granite-greenstone craton. The confinement of a suite of alkaline igneous rocks to this shear zone is a notable feature. The strike extensions of this shear belt extend through to the Elchuru alkaline complex, Prakasam District, Andhra Pradesh, and the syenite plutons of Koraput district, Orissa. The contrasting lithologies, metamorphism and structural history on either side of the shear zone suggests that it might be a Precambrian suture zone. The mesoscopic structural features in the EGMB include prominent foliation with moderate to steep dips, folds, faults/shears, S-C fabrics, pinch and swell structures and other linear fabric elements. These observations favour the consideration of drastic crustal shortening and thickening and a complex deformational sequence. The major rock units in this part of EGMB comprise garnetiferous sillimanite gneisses, quartzites and calc-granulites forming the khondalitic suite of rocks and a wide variety of charnockitic rocks. The contact of the two rock units is generally sheared and often migmatised. The structural fabric suggests two major tectonic events: an essentially horizontal tectonic regime resulting in thrust systems and associated structures, subsequently followed by strike-slip tectonics characterized by high shear strains. Features such as westward-verging thrusts, large-scale recumbent folds, major shear zones, structural domes and basins, indications of tectonic crustal shortening, extensive calc-alkali magmatism and widespread migmatization in the region are attributed to collisional processes during Proterozoic times. The spatial disposition of the EGMB and its linkage with the distribution of similar rock units during the late Precambrian time in a global tectonic scenario are discussed. 相似文献
3.
The AravallieDelhi and Satpura Mobile Belts(ADMB and SMB)and the Eastern Ghat Mobile Belt(EGMB)in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins.The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions,crustal thickening(w45 km)and high density and high conductivity rocks in upper/lower crust associated with faults/thrusts.These observations indicate convergence while domal type refectors in the lower crust suggest an extensional rifting phase.In case of the SMB,even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to w120 km across the PurnaeGodavari river faults has been traced which may be caused by fuids due to metamorphism.Subduction related intrusives of the SMB south of it and the ADMB west of it suggest NeS and EeW directed convergence and subduction during MesoeNeoproterozoic convergence.The simultaneous EeW convergence between the Bundelkhand craton and Marwar craton(Western Rajasthan)across the ADMB and the NeS convergence between the Bundelkhand craton and the Bhandara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NEeSW direction with EeW and NeS components in the two cases,respectively.This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part.The Eastern Ghat Mobile Belt(EGMB)also shows signatures of E eW directed MesoeNeoproterozoic convergence with East Antarctica similar to ADMB in north India.Foreland basins such as Vindhyan(ADMBeSMB),and Kurnool(EGMB)Supergroups of rocks were formed during this convergence.Older rocks such as Aravalli(ADMB),MahakoshaleBijawar(SMB),and Cuddapah(EGMB)Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts,plausibly formed during an earlier episode of rifting during PaleoeMesoproterozoic period.They are highly disturbed and deformed due to subsequent MesoeNeoproterozoic convergence.As these Paleoproterozoic basins are characterized by large scale basic/ultrabasic intrusives that are considerably wide spread,it is suggested that a plume/superplume might have existed under the Indian cratons at that time which was responsible for the breakup of these cratons.Further,the presence of older intrusives in these mobile belts suggests that there might have been some form of convergence also during Paleoproterozoic period. 相似文献
4.
5.
D.Malleswari K.Veeraswamy K.K.Abdul Azeez A.K.Gupta Narendra Babu Prasanta K.Patro T.Harinarayana 《地学前缘(英文版)》2019,10(5):1915-1930
Broad-band and long period magnetotelluric measurements made at 63 locations along ～500 km long Chikmagalur-Kavali profile,that cut across the Dharwar craton(DC)and Eastern Ghat Mobile Belt(EGMB)in south India,is modelled to examine the lithosphere architecture of the cratonic domain and define tectonic boundaries.The 2-D resistivity model shows moderately conductive features that intersperse a highly resistive background of crystalline rocks and spatially connect to the exposed schist belts or granitic intrusions in the DC.These features are therefore interpreted as images of fossil pathways of the volcanic emplacements associated with the greenstone belt and granite suite formation exposed in the region.A near vertical conductive feature in the upper mantle under the Chitradurga Shear Zone represents the Archean suture between the western and eastern blocks of DC.Although thick(～200 km)cratonic(highly resistive)lithosphere is preserved,significant part of the cratonic lithosphere below the western DC is modified due to plume-continental lithosphere interactions during the Cretaceous—Tertiary period.A west-verging moderately conductive feature imaged beneath EGMB lithosphere is interpreted as the remnant of the Proterozoic collision process between the Indian land mass and East Antarctica.Thin(～120 km)lithosphere is seen below the EGMB,which form the exterior margin of the India shield subsequent to its separation from East Antarctica through rifting and opening of the Indian Ocean in the Cretaceous. 相似文献
6.
This paper intends to explore whether there is an important source for monazite beach placer of the Gopalpur-Chhatrapur-Rushikulya
coast, Orissa, in the adjacent Eastern Ghat Mobile Belt (EGMB). Petrographic and mineralogical studies were conducted on all
the rock types constituting the EGMB exposed over a stretch extended up to ∼20 km landward from the estuary of the River Rushikulya
that is believed to transport the major bulk of sand to the Gopalpur-Chhatrapur-Rushikulya beach. Heavy mineral population
was concentrated using bromoform and percentages of each heavy mineral constituting the population were estimated for all
the potential source rock types. Isodynamic separation and XRD techniques were deployed for precision identification of every
heavy mineral present. The study identified the granitoid (or migmatite) basement rock as by far the major contributor of
monazite to the Chhatrapur beach sand. The study also reveals that charnockite is an important contributor of orthopyroxene
as well as garnet, although the sillimanite-garnet-quartz schist (khondalites) is also an important source for the latter.
On the other hand, garnet-quartz schist and garnet-biotite-quartz schist may also contribute substantial quantity of pyroxene
and garnet. The high grade metasedimentary rocks, in general, could be the major sources for rutile, while ilmenite, magnetite
and zircon in the beach sand have their sources perhaps in all the varieties of rocks constituting the EGMB. 相似文献
7.
《Precambrian Research》2001,105(2-4):143-164
New fieldwork, map interpretation, petrography and single zircon U–Pb geochronology has allowed the identification of different crustal blocks in the Paamiut region, in the southern portion of the West Greenland Archaean Craton. Changes of metamorphic grade from only amphibolite facies to granulite facies (some subsequently retrogressed) corresponds with zones of Archaean high strain ductile deformation ± mylonites. U–Pb zircon dates are presented for the TTG (tonalite, trondhjemite, granodiorite) protoliths from each block in the Paamiut region, and the southern portion of the previously identified Tasiusarsuaq terrane lying to the north. The southern part of the Tasiusarsuaq terrane contains 2880–2860 Ma TTG rocks and underwent amphibolite facies metamorphism. Structurally underneath the Tasiusarsuaq terrane to the south is the Sioraq block containing 2870–2830 Ma TTG rocks partly retrogressed from granulite facies. Structurally underneath and to the south is the Paamiut block, dominated by 2850–2770 Ma granodioritic rocks that have only undergone amphibolite facies metamorphism. Also structurally overlying the Paamiut block, but cropping out separately from the Sioraq block, is the Neria block. This appears to be dominated by 2940–2920 Ma gneisses that have been totally retrogressed from granulite facies and strongly deformed. In the southernmost part of the region the Neria block overlies the greenschist to lowermost amphibolite facies Sermiligaarsuk block that contains the ⩾2945 Ma Tartoq Group. Rocks from all the blocks record ancient loss of Pb from zircons and some new zircon growth at 2820 Ma, interpreted to indicate a high grade metamorphic event at that time, including granulite facies metamorphism in the Sioraq and Neria blocks. The blocks of different metamorphic grade are interpreted to have moved to their current positions after the 2820 Ma metamorphism, explaining the change in metamorphic history across some mylonites and ductile shear zones which deform and retrogress granulite facies textures. The juxtaposed blocks and their contacts were subsequently folded under amphibolite facies conditions. The contacts are cut by undeformed Palaeoproterozoic dolerite dykes which post-date amphibolite facies metamorphism. These results, together with previously published data from the Godthåbsfjord region (north of Paamiut) shows that the North Atlantic Craton in West Greenland from Ivittuut in the south to Maniitsoq in the north (∼550 km) consists of a mosaic of ductile fault-bounded packages that attained their present relative positions in the late Archaean. 相似文献
8.
《Journal of Asian Earth Sciences》2011,40(6):537-550
The Eastern Ghats Frontal Thrust (EGFT) demarcates the boundary between the Archaean/Paleoproterozoic cratonic rocks to the west, and the Meso/Neoproterozoic granulites of the Eastern Ghats Mobile Belt (EGMB) to the east. At Jeypore (Orissa, India), mafic schists and granites of the cratonic domain document a spatial increase in the metamorphic grade from greenschist facies (garnet, clinozoisite – absent varieties) in the foreland to amphibolite facies (clinozoisite- and garnet-bearing variants) progressively closer to the EGFT. Across the EGFT, the enderbite–charnockite gneisses and mafic granulites of EGMB preserves a high-grade granulite facies history; amphibolite facies overprinting in the enderbite–charnockite gneisses at the cratonic fringe is restricted to multi-layered growth of progressively Al, Ti – poor hornblende at the expense of pyroxene and plagioclase. In associated mafic granulites, the granulite facies gneissic layering is truncated by sub-centimeter wide shear bands defined by synkinematic hornblende + quartz intergrowth, with post-kinematic garnet stabilized at the expense of hornblende and plagioclase. Proximal to the contact, these granulites of the Eastern Ghats rocks are intruded by dolerite dykes. In the metadolerites, the igneous assemblage of pyroxene–plagioclase is replaced by intergrown hornblende + quartz ± calcite that define the thrust-related fabric and are in turn mantled by coronal garnet overgrowth, while scapolite is stabilized at the expense of recrystallized plagioclase and calcite. Petrogenetic grid considerations and thermobarometry of the metamorphic assemblages in metadolerites intrusive into granulites and mafic schists within the craton confirm that the rocks across the EGFT experienced prograde heating (Tmax value ∼650–700 °C at P ∼ 6–8 kbar) along the prograde arm of a seemingly clockwise P–T path. Since the dolerites were emplaced post-dating the granulite facies metamorphism, the prograde heating is correlated with renewed metamorphism of the granulites proximal to the EGFT. A review of available age data from rocks neighboring the EGFT suggests that the prograde heating of the cratonic granites and the re-heating of the Eastern Ghats granulites are Pan – African in age. The re-heating may relate to an Early Paleozoic Pan-Gondwanic crustal amalgamation of older terrains or reactivation along an old suture. 相似文献
9.
桐柏-大别山区高压变质相的构造配置 总被引：18，自引：3，他引：15
作为华北和扬子陆块间的碰撞造山带桐柏大别山区以发育高压、超高压变质带为特征,从南到北变质相从低级到高级,代表俯冲带深度不同的变质产物,整体形成高压变质相系列。不过现今各变质相岩石的分布极受后期地壳规模的伸展构造控制,大别杂岩的穹隆作用更使高压变质相带的空间分布复杂化。超高压变质岩今日多呈大小不等的块体嵌布于相对低压的大别杂岩之内,造山带根部物质的热软化,使许多深层地幔物质得以像挤牙膏一样挤出于大别杂岩内。它们之中广泛发育着减压退变质的显微结构,与大别杂岩内一些麻粒岩相表壳岩所保存的减压退变质证迹一样,同是挤出作用和碰撞后隆升的构造证迹。高压相系的发育使南桐柏山和大别山迥然不同于桐商（ 商丹） 断裂以北的北秦岭北淮阳变质带。新近发表的同位素年代学（４０Ａｒ ３９ Ａｒ） 资料：３１６ ～４３４ Ｍａ ,已证明北秦岭是古生代变质带,它与桐柏－ 大别印支期碰撞造山带差异甚大。这两个变质地温梯度差异甚大的变质地体的拼合,说明华北和扬子陆块碰撞的主缝合带是商丹－ 桐商断裂带 相似文献
10.
大别山北大别杂岩的大地构造属性 总被引：12，自引：1，他引：11
北大别杂岩主要由花岗质片麻岩及斜长角闪岩组成 ,含有不同类型、大小不等的麻粒岩岩块和变质超镁铁质岩块 ,侵入有大量白垩纪花岗岩和辉石 -辉长岩类。其中的花岗质片麻岩、斜长角闪岩具有岛弧环境的岩石地球化学特征 ,代表拼贴于扬子陆块北缘的新元古代古岛弧。北大别杂岩北可与庐镇关群相连 ,南俯于超高压变质岩之下 ,在三叠纪扬子陆块与华北陆块的碰撞过程中 ,曾与超高压变质岩一起俯冲到地幔深度并经受榴辉岩相变质作用 ,然后在折返过程中叠加了麻粒岩相及角闪岩相变质作用 ,是扬子陆块北缘陆壳俯冲基底的一部分 相似文献
11.
In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and amphibolite facies rocks of the Rengali Province.At present,the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin,and in the Rengali Province to the north.Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB(wt15 mGal),through the basin(w 10 mGal),into the Rengali Province(w 15 mGal).The data are consistent with the reportedly uncompensated nature of the EGMB,and indicate that the crust below the Rengali Province has a cratonic gravity signature.The contact between the two domains with distinct sub-surface structure,inferred from gravity data,coincides with the North Orissa Boundary Fault(NOBF)that defnes the northern boundary of the Talchir Basin.Post-Gondwana faults are also localized along the northern margin of the basin,and present-day seismic tremors also have epicenters close to the NOBF.This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary,and continues to be susceptible to seismic activity even at the present-day. 相似文献
12.
Abstract: The Karlapat bauxite deposit occurs in the Eastern Ghat Group of rocks in Orissa and has developed in the khondalites. Mineralogical and physical observations on bore hole samples reflect the presence of a maximum of six weathered zones from top to bottom. These zones are termed as topsoil, siliceous laterite, ferruginous laterite, bauxite, lithomarge and altered khondalite. Four-dimensional trend surface models are developed for the data of 45 and 36 bore holes from north and south blocks, respectively, on Al2 O3 and SiO2 to delineate the zones of metallurgical grade bauxite (SiO2 5 % and Al2 O3 40 %). The results indicate about 15 m thickness of bauxite in the north block while it could be up to 20 m thick in the south block, leaving about 10 m of lat-erites at the top of each block. High grade bauxite (>47 % Al2 O3 ) is also encountered at specific locations. 相似文献
13.
Stable isotope geochemistry of marbles from the coesite UHP terrains of Dabieshan and Sulu, China 总被引：21，自引：0，他引：21
Marbles from Dabieshan and Sulu, China, suffered ultra high pressure (UHP) metamorphism in the coesite–eclogite facies at approximately 700°C and 30 kbars during Triassic continental collision and subduction. The marbles range in isotopic composition from +7 to +25 δ18OVSMOW and from 0 to +6 δ13CVPDB. High δ13C values are representative of unmodified protoliths and are similar to those of 13C-enriched Sinian carbonate rocks from the Yangtze craton. High oxygen isotope ratios reflect pristine protoliths but the low values may have been caused by infiltration of low 18O meteoric water during diagenesis and dolomitization, by fracture-controlled infiltration of water during subduction, by metamorphic mineral reactions, or by a combination of these processes. No evidence of regional isotopic transport during UHP metamorphism has been found. Sampling on scales of 1 to 100 m shows marbles to be inhomogeneous in both carbon and oxygen isotopes. Only samples separated by less than 10 cm have equilibrated oxygen and carbon isotope compositions. Limited isotopic equilibration between adjacent rocks is consistent with the preservation of unaltered UHP minerals and indicates that the metamorphic fluid–rock system was rock-dominated during and following peak metamorphism. A freely flowing, pervasive fluid phase was not present during UHP metamorphism. There is no evidence of isotopic exchange between marble and the upper mantle into which it was subducted. Correlation of geochemical similarities of UHP marbles with Sinian limestones implies that the subducted edge of the Yangtze craton extends at least as far north as the coesite–eclogite facies rocks of Dabieshan. Deposition of protolith carbonates may have taken place in a cold climate either preceding or following but not coincident with Neoproterozoic glaciation. 相似文献
14.
大别地区的变质作用及与碰撞造山过程的关系 总被引：3，自引：0，他引：3
大别造山带从南到北可分为５个变质构造单元：扬子北缘蓝片岩带、突松变质杂岩带、南大虽碰撞杂岩带、北大别变质杂岩带和北淮阳变质带。各个变质构造单元中不同岩石的变质作用可划分为３种类型：（１）超高压型。以含柯石英（及金刚石）的榴辉岩为代表,仅见于南大别碰撞杂岩带中,这类岩石的ＰＴ轨迹反映洋壳Ｂ型俯冲的特点。（２）高压型。见于大别山南部的蓝片岩带、宿松变质杂岩带和南大别杂岩中的变质沉积岩及部分片麻岩中,与 相似文献
15.
东昆仑前寒武纪基底变质岩系的锆石SHRIMP年龄及其构造意义 总被引：29，自引：1，他引：28
东昆仑地区有一系列前寒武纪变质基底岩系出露 ,这些基底岩块可以划分为两类 :北部基底以太古宙—古元古代的白沙河岩群和中元古代的小庙岩群为代表 ,南部基底以古、中元古代苦海杂岩为代表。对北部基底岩系小庙岩群变质碎屑岩系的锆石U PbSHRIMP年龄分析结果显示小庙岩群(Pt2 x)碎屑物源区是年龄大于 2 4亿年的岩石 ,2 4～ 2 5亿年的碎屑锆石的群组年龄很可能反映了小庙岩群源区的一期变质作用时间。个别 32亿年的碎屑锆石年龄指示源区存在古太古代的陆核。变质锆石及深熔成因的锆石给出的 10 35～ 10 74Ma群组年龄是小庙岩群的主期构造热事件时间 ,反映以清水泉蛇绿岩为代表的中元古代洋盆的闭合和南北不同基底块体的愈合 ,是Rodinia大陆聚合事件在东昆仑地区的表现。 相似文献
16.
鄂尔多斯盆地延长组长7沉积期物源分析及母岩类型研究 总被引：2，自引：0，他引：2
通过对鄂尔多斯盆地延长组长7砂岩的类型、轻重矿物特征、重矿物聚类分析及泥岩的地化特征研究,并结合盆地周边源区露头剖面的岩性组合资料,讨论了长7沉积期的物源方向,恢复各源区母岩性质。经研究表明:鄂尔多斯盆地长7沉积期存在五个方向物源,东北、西南为主要的物源方向,西北、南部作为次要物源方向;其中东北源区母岩以中基性岩浆岩、高级变质岩为主,西南源区母岩以白云岩、浅变质岩为主,西北源区母岩以沉积岩为主,浅变质岩次之,南部源区母岩以含灰岩、碎屑岩为主,浅变质岩次之;另外经讨论证实西部存在局限的物源供给区,母岩主要为白云岩。 相似文献
17.
Marine magnetic anomalies along three representative profiles falling between shelf break and continent–ocean boundary in the offshore Krishna–Godavari basin were quantitatively interpreted for understanding the nature and structure of the magnetic basement using inversion technique. The interpretation of the anomalies shows that the magnetic basement lies deeper than the base of the sediments, i.e., acoustic basement identified by the seismic studies. This interpretation also shows that the magnetic basement is faulted along the NW–SE direction with the upthrown side lying to the north of the anomaly trend of this region. The coincidence of magnetizations observed through the present interpretation with that of charnockites of neighbouring EGMB and onshore K–G basin areas indicates that EGMB geology (charnockites, granitic gneiss, etc.) extends up to COB in the offshore K–G basin. 相似文献
18.
Chen Nengsong Zhang Kexin Wang Guocan Hou Guangjiu Zhu Yunhai Faculty of Earth Sciences China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1998,9(3)
ＴｈｅＣｅｎｔｒａｌＭｏｕｎｔａｉｎＲａｎｇｅｓｏｆＣｈｉｎａ,ｗｈｉｃｈｏｃｕｐｙｔｈｅｃｅｎｔｒａｌｐａｒｔｏｆＣｈｉｎａ,ｃｏｍｐｒｉｓｅｍａｉｎｌｙｔｈｅＤａｂｉｅＭｏｕｎ－ｔａｉｎｓｉｎｔｈｅｅａｓｔ,ｔｈｅＱｉｎｌｉｎｇＭｏｕｎｔａｉｎｓ... 相似文献
19.
The Xes-Xen dating of zircons from rocks of the Rayner Complex of the Enderby Land at the Molodezhnaya Station area (coast of the Alasheyev Bight) yielded age estimates of 550 ± 50 and 1040 ± 30 Ma. The metamorphic rocks of the Rayner Complex record two main events: first, the crystallization of the magmatic protoliths of charnockitic and enderbitic gneisses and, second, superimposed structural and metamorphic alterations under conditions transitional from the amphibolite to granulite facies (metamorphism manifested regionally in the rocks of the Rayner Complex). The most reliable Xes-Xen age estimates for magmatic zircons from the charnockitic and enderbitic gneisses correspond to the Grenville stage of the development of the Rayner Complex (～1.0 Ga). The Xe isotopic systematics of metamorphic zircons reflect a pan-African stage in the evolution of the Rayner Complex (600–550 Ma). Pan-African events are reflected in the U-Xe isotope system in two cases: if metamorphic zircons crystallized at the same time (which probably resulted in the formation of a plateau in the Xes-Xen age spectrum) and if the initial isotopic systems were disturbed (which resulted in a decrease in apparent age toward low-temperature gas fractions). It is important that secondary alterations and a decrease in apparent ages to 600–550 Ma affected only those components (i.e., caused xenon release only from those traps) that were unstable under the maximum metamorphic temperatures and yielded T cl values lower than 750°C (conditions transitional from the amphibolite to granulite facies). At a higher xenon retention, “primary” isotopic systems are preserved. Consequently, the age of metamorphism transitional between the amphibolite and granulite facies can be estimated at 600–550 Ma on the basis of Xes-Xen dating. In general, the results of our study indicate that the age of regional metamorphism of the Rayner complex at the Molodezhnaya area is approximately 600–550 Ma rather than ～1.0 Ga, as was previously supposed. 相似文献
20.
The relation between alkaline magmatism and tectonism has been a contentious issue, particularly for the Precambrian continental
regions. Alkaline complexes at the southwestern margin of Eastern Ghats belt, India, have been interpreted as rift-valley
magmatism. However, those complexes occurring in granulite ensemble in the interior segments of the Eastern Ghats belt could
not possibly be related to the rift-system, assumed for the western margin of the Eastern Ghats belt. Koraput complex was
emplaced in a pull-apart structure, dominated by magmatic fabrics and geochemically similar to a fractionated alkaline complex,
compatible with an alkalibasalt series. Rairakhol complex, on the other hand, shows dominantly solid-state deformation fabrics
and geochemically similar to a fractionated calc-alkaline suite. Isotopic data for the Koraput complex indicate ca. 917 Ma
alkaline magmatism from a depleted mantle source and postcrystalline thermal overprint at ca. 745 Ma, also recorded from sheared
metapelitic country rocks. The calc-alkaline magmatism of the Rairakhol complex occurred around 938 Ma, from an enriched mantle
source, closely following Grenvillian granulite facies imprint in the charnockitic country rocks. 相似文献