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1.
Geochemical studies of granitoids from Shyok tectonic zone of Khardung-Panamik section,Ladakh, India
The Shyok tectonic zone lies to the north of Ladakh magmatic arc or the Ladakh batholith in the Trans-Himalaya of Ladakh district,
J & K. Investigations were carried out on the granitoids exposed along Leh-Siachan highway between Khardung and Panamik villages.
The granitoid bodies under study are: Khardung granite (KG), Tirit granite (TG) and Panamik granite (PG) belonging to Ladakh
batholith, Shyok ophiolitic mélange and Karakoram batholith respectively. Though the granitoids belong to different litho-tectonic
units, yet they have subduction related geochemical characters typical of Andean-type granitoids. Re-melting of crustal rocks
of volcanic arc affinity has played an important role for the origin of KG rocks which are more evolved, while the TG and
PG rocks represent transitional tectonic environment from primitive to mature arc. 相似文献
2.
V. C. Thakur 《Journal of Earth System Science》1990,99(2):169-185
The Indus Tsangpo suture zone in Ladakh lies between the Phanerozoic sequence of the Zanskar Zone of Tethys Himalaya in the
south and Karakoram zone in the north. The five palaeotectonic regimes recognized in the suture zone are: The Indus palaeosubduction
complex, the Ladakh magmatic arc, the Indus arc-trench gap sedimentation, the Shyok backarc and the Post-collision molasse
sedimentation. The Ladakh magmatic arc, comprising intrusives of the Ladakh plutonic complex and extrusives of the Dras, Luzarmu
and Khardung formations, owes its origin to the subduction of the Indian oceanic plate underneath the Tibet-Karakoram block.
The Indus Formation, lower Cretaceous to middle Eocene in age, was laid down in a basin between the magmatic arc and the subduction
complex. The Shergol and Zildat ophiolitic melange belts exhibit green-schist and blue-schist facies metamorphism and show
structural geometry and deformation history dissimilar to that of the underlying and overlying formations. The melange belts
and the flysch sediments of the Nindam Formation represent a palaeosubduction complex. The Shyok suture zone consists of tectonic
slices of metamorphics of the Pangong Tso Crystallines, Cretaceous to lower Eocene volcanics and sedimentaries, together with
ultramafic and gabbro bodies and molasse sediments. This petrotectonic assemblage is interpreted as representing a back-are
basin. Post-collision molasse sedimentaries are continental deposits of Neogene age, and they occur with depositional contact
transgressing the lithological and structural boundaries. Two metamorphic belts, the Tso Morari crystalline complex and the
Pangong Tso Crystallines, flank to the south and north respectively of the Indus suture zone in Eastern Ladakh. Three generations
of fold structures and associated penetrative (and linear) structures, showing a similar deformation history of both the metamorphic
belts, are developed. The shortening structures developed as a result of collision during the postmiddle Eocene time. 相似文献
3.
In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone. 相似文献
4.
New geological observations, recent published data and U–Pb SHRIMP zircon dating from the Karakoram Mountains along the Nubra and Shyok Rivers reveal that the initial subduction of the Tethyan oceanic lithosphere took place ~ 110 Ma beneath the Paleozoic–Mesozoic platform of the southern edge of the Asian Plate. This has produced the I-type plutons within the Karakoram Batholith Complex, well before the juxtaposition of the Asian Plate along the Karakoram Shear Zone. Within this shear zone, U–Pb zircon crystallisation ages of ~ 75 Ma from mylonitised granitoids and 68 Ma from undeformed Tirit granodiorite constrain the timing of suturing of the Karakoram terrain with the Trans-Himalaya between 75 and 68 Ma. Post-shearing leucogranite was episodically generated within frontal migmatised Karakoram Metamorphic Belt and emplaced between 20 and 13 Ma within the shear zone. Presence of a low resistivity zone as a possible indication of mid-crustal partial molten crust underneath the Higher Himalaya–Ladakh–Karakoram terrains manifests the impingement of the Indian Plate along the Main Himalayan Thrust at depth.
Physical continuity of the Baltoro granite belt into the Karakoram Batholith is established as well as the continuity of the Shyok suture as the Shiquanhe Suture Zone in western Tibet through the Chushul–Dungti sector. The Karakoram Shear Zone, therefore, displays a complex geological history of movements since ~ 75 Ma and plays a very significant role in the overall India–Asia convergence, rather than merely being a strike-slip fault for eastward extrusion of a segment of Asia in Tibet. 相似文献
5.
Santosh Kumar Sita Bora Umesh K. Sharma 《Journal of the Geological Society of India》2016,87(6):737-746
New field observations on granitoids and associated lithounits in some parts of Indus-Shyok Suture Zones have been documented in order to re-establish the geological relationships between various volcano-plutonic magmatic lithounits. Careful examination of outcrops and contact relationships between the various lithounits have pin-pointed the sequence of geological events. Field features of granitoids exposed along Leh-Saboo-Khardung_La suggest multiple pulses of mafic-felsic magma interactions (mingling to mixing) with almost 25% of the mafic to hybrid magma input in the evolution of the eastern part of Ladakh batholith. Along Khardung_La-Shyok-Diskit, thick sequence of volcanic lithounits is exposed, which dominantly consist of massive basaltic andesite, porphyritic andesite, dacite and rhyolite forming Khardung Formation. On the other hand Shyok Formation, dipping opposite to the Khardung Formation, composed predominantly of meta-sedimentary lithounits and subordinate amount of volcanic materials at present exposed level. Spectacular intrusive contacts of Ladakh granitoids with metavolcanics and meta-sedimentary country rocks of Shyok Formation near Diskit can be observed, which are manifested by ubiquitous xenoliths near the marginal parts. Although the nature of granitoid melt invasion into country-rocks was relatively winty, granitoid melt has produced leucogranite-pegmatite system because of devolatization and decompression effects. Frequent xenoliths of porphyritic andesite and dacite roof pendants are being reported in Tirit granitoids, which strongly suggest sub-volcanic emplacement of granitoid melt, extensive assimilation and roof collapse of overlying volcanic materials. It is more likely that the xenoliths hosted in Tirit granitoids belong to Shyok volcanics. It is suggested that multiple pulses of coeval mafic and felsic magmatism occurred extensively and emplaced at differential crustal levels. 相似文献
6.
In situ U‐Th/Pb (LA‐ICP‐MS) monazite ages from the Hindu Kush of NW Pakistan provide new petrochronologic constraints on the tectonic evolution of the Himalaya–Karakoram–Tibet orogen. Monazites from two adjacent garnet + staurolite schist specimens yield multiple age populations that record the major Mesozoic and Cenozoic deformational, magmatic and metamorphic events along the southern margin of Eurasia. These include the accretion of the Hindu Kush–SW Pamir to Eurasia during the Late Triassic, followed by the accretion of the Karakoram terrane in the Early Jurassic. Younger Jurassic and Cretaceous ages record the development of an Andean‐style volcanic arc along the southern Eurasian margin, which ended with the docking of the Kohistan island arc and the emplacement of the Kohistan–Ladakh batholith during the Late Cretaceous. The initial Eocene collision of India with Eurasia was followed by widespread high‐temperature metamorphism and anatexis associated with crustal thickening within the Himalaya system in the Late Oligocene and Early Miocene. 相似文献
7.
《Journal of Asian Earth Sciences》2002,20(3):309-351
The Shyok Suture Zone (Northern Suture) of North Pakistan is an important Cretaceous-Tertiary suture separating the Asian continent (Karakoram) from the Cretaceous Kohistan–Ladakh oceanic arc to the south. In previously published interpretations, the Shyok Suture Zone marks either the site of subduction of a wide Tethyan ocean, or represents an Early Cretaceous intra-continental marginal basin along the southern margin of Asia. To shed light on alternative hypotheses, a sedimentological, structural and igneous geochemical study was made of a well-exposed traverse in North Pakistan, in the Skardu area (Baltistan). To the south of the Shyok Suture Zone in this area is the Ladakh Arc and its Late Cretaceous, mainly volcanogenic, sedimentary cover (Burje-La Formation). The Shyok Suture Zone extends northwards (ca. 30 km) to the late Tertiary Main Karakoram Thrust that transported Asian, mainly high-grade metamorphic rocks southwards over the suture zone.The Shyok Suture Zone is dominated by four contrasting units separated by thrusts, as follows: (1). The lowermost, Askore amphibolite, is mainly amphibolite facies meta-basites and turbiditic meta-sediments interpreted as early marginal basin rift products, or trapped Tethyan oceanic crust, metamorphosed during later arc rifting. (2). The overlying Pakora Formation is a very thick (ca. 7 km in outcrop) succession of greenschist facies volcaniclastic sandstones, redeposited limestones and subordinate basaltic–andesitic extrusives and flow breccias of at least partly Early Cretaceous age. The Pakora Formation lacks terrigenous continental detritus and is interpreted as a proximal base-of-slope apron related to rifting of the oceanic Ladakh Arc; (3). The Tectonic Melange (<300 m thick) includes serpentinised ultramafic rocks, near mid-ocean ridge-type volcanics and recrystallised radiolarian cherts, interpreted as accreted oceanic crust. (4). The Bauma–Harel Group (structurally highest) is a thick succession (several km) of Ordovician and Carboniferous to Permian–Triassic, low-grade, mixed carbonate/siliciclastic sedimentary rocks that accumulated on the south-Asian continental margin. A structurally associated turbiditic slope/basinal succession records rifting of the Karakoram continent (part of Mega–Lhasa) from Gondwana. Red clastics of inferred fluvial origin (‘molasse’) unconformably overlie the Late Palaeozoic–Triassic succession and are also intersliced with other units in the suture zone.Reconnaissance further east (north of the Shyok River) indicates the presence of redeposited volcaniclastic sediments and thick acid tuffs, derived from nearby volcanic centres, presumed to lie within the Ladakh Arc. In addition, comparison with Lower Cretaceous clastic sediments (Maium Unit) within the Northern Suture Zone, west of the Nanga Parbat syntaxis (Hunza River) reveals notable differences, including the presence of terrigenous quartz-rich conglomerates, serpentinite debris-flow deposits and a contrasting structural history.The Shyok Suture Zone in the Skardu area is interpreted to preserve the remnants of a rifted oceanic back-arc basin and components of the Asian continental margin. In the west (Hunza River), a mixed volcanogenic and terrigenous succession (Maium Unit) is interpreted to record syn-deformational infilling of a remnant back-arc basin/foreland basin prior to suturing of the Kohistan Arc with Asia (75–90 Ma). 相似文献
8.
40Ar–39Ar geochronological studies carried out on the Khardung volcanics of Ladakh, India and our earlier Ar–Ar results from the volcanics of the Shyok suture along with the available geological and geochemical data provide good constraints for post-collision evolution of the Shyok suture zone. Whole-rock samples from the Shyok volcanics yielded disturbed age-spectra and we have demonstrated earlier that the youngest tectonic event in the Shyok suture zone responsible for the thermal disturbance of these samples is Karakoram fault activation at ～14 Ma. Contrastingly whole-rock samples from the Khardung volcanics, which are in tectonic contact with these Shyok volcanics, and are exposed in the form of thick rhyolitic and ignimbritic flows, yielded undisturbed age-spectra and good plateau-ages. The whole-rock plateau-ages of two rhyolite samples are 52.8 ± 0.9 and 56.4 ± 0.4 Ma. We interpret these ages to be the time and duration of emplacement of these volcanics over thickened margin of the continental crust, which appears to be coeval with the initiation of the collision between the Indian and Asian plate. The lesser extent of post-emplacement isotopic re-equilibration in these samples unlike the Shyok volcanics indicate that these samples were present in different tectonic settings, away from the Karakoram fault, at the time of deformation in the Shyok suture zone. We propose that the two volcanic belts of contrasting nature were brought together in juxtaposition by the Karakoram strike slip faulting at ～14 Ma. 相似文献
9.
The trans-Himalayan Ladakh batholith is a result of arc magmatism caused by the northward subduction of the Tethyan oceanic lithosphere below the edge of the Eurasian plate. The batholith dominantly consists of calc-alkaline I-type granitoids which are ferromagnetic in nature with the presence of magnetite as the principal carrier of magnetic susceptibility. The mesoscopic and magnetic fabric are concordant and generally vary from WNW–ESE to ENE–WSW for different intrusions of ferromagnetic granites in different parts of the batholith. Strike of magnetic fabric is roughly parallel with the regional trend of the Ladakh batholith in the present study area and is orthogonal to the direction of India-Eurasia collision. In Khardungla and Changla section, the magnetic fabric is distributed in a sigmoidal manner. It is inferred that this sigmoidal pattern is caused by shearing due to transpression induced by oblique convergence between the two plates. U–Pb zircon geochronology of a rhyolite from the southern parts of the batholith gives a crystallization age of 71.7 ± 0.6 Ma, coeval with ~68 Ma magmatism in the northern parts of the batholith. The central part of the batholith is characterized by S-type two-mica granites, which gives much younger age of magmatism at 35.5 ± 0.5 Ma. The magnetic fabric of these two-mica granites is at a high angle to the regional trend of the batholith. It is proposed that these two-mica granites were emplaced well after the cessation of subduction and arc magmatism, along fractures that developed perpendicular to the regional strike of the batholith due to shearing. 相似文献
10.
A PETROLOGICAL OVERVIEW OF THE KOHISTAN MAGMATIC ARC, NW HIMALAYA, N. PAKISTAN1 TahirkheliRAK ,MattauerM .ProustF ,etal.1979.In :GeodynamicsofPakistan[C].FarahA ,DeJongKA ,eds.GeolSurvPakistan ,Quetta ,1979.12 5～ 130 .
2 CowardMP ,WindleyBF ,BroughtonRD ,etal.In :CollisionTectonics[C]..CowardMP ,RiesAC ,eds.GeolSoc,London ,SpecPub ,1986 ,19:2 0 3～ 2 19.
3 BardJP ,MaluskiH ,MattePh ,etal.GeolBull ,PeshawarUniversity ,1980 ,13:87～ 93.
… 相似文献
11.
Shelf, forereef and basin margin (slope) olistoliths (Exotic blocks of limestone) of Permian–Jurassic age are tectonically juxtaposed within the Triassic to Eocene age pre-orogenic, deep abyssal plain turbidites of the Lamayuru. The pre-collision tectonic setting and depositional environment of the limestone olistoliths can be reconstructed from within the neighbouring Zanskar range. The disorganized Ophiolitic Melange Zone, an association of different tectonic rock slivers of Jurassic–Eocene age, is tectonically underlain by the overthrusted Lamayuru Formation and tectonically overlain by the Nindam Formation. Tectonic slivers of Late Jurassic–Early Cretaceous age red radiolarian cherts represent a characteristic lithotectonic unit of the Ophiolitic Melange Zone, those occurring near the contact zone with the Lamayuru Formation, were deposited within the neo-Tethyan deep-ocean floor of the Indian passive margin below the carbonate compensation depth. These tectonic slivers accumulated along the northern margin of the Indus–Yarlung Suture Zone of the Ladakh Indian Himalaya during subduction accretion associated with the initial convergence of the Indian plate beneath the Eurasian plate. 相似文献
12.
STRUCTURAL AND THERMAL EVOLUTION OF THE SOUTH ASIAN CONTINENTAL MARGIN ALONG THE KARAKORAM AND HINDU KUSH RANGES,NORTH PAKISTAN 相似文献
13.
GENESIS OF COPPER MINERALIZATION IN THE WESTERN KOHISTAN ISLAND ARC TERRANE,NW HIMALAYA—HINDUKUSH, N. PAKISTAN 总被引：1，自引：0，他引：1
GENESIS OF COPPER MINERALIZATION IN THE WESTERN KOHISTAN ISLAND ARC TERRANE,NW HIMALAYA—HINDUKUSH, N. PAKISTAN 相似文献
14.
Oliver Jagoutz Max W. Schmidt Andreas Enggist Jean-Pierre Burg Dawood Hamid Shahid Hussain 《Contributions to Mineralogy and Petrology》2013,166(4):1099-1118
We present the geochemistry and intrusion pressures of granitoids from the Kohistan batholith, which represents, together with the intruded volcanic and sedimentary units, the middle and upper arc crust of the Kohistan paleo-island arc. Based on Al-in-hornblende barometry, the batholith records intrusion pressures from ~0.2 GPa in the north (where the volcano-sedimentary cover is intruded) to max. ~0.9 GPa in the southeast. The Al-in-hornblende barometry demonstrates that the Kohistan batholith represents a complete cross section across an arc batholith, reaching from the top at ~8–9 km depth (north) to its bottom at 25–35 km (south-central to southeast). Despite the complete outcropping and accessibility of the entire batholith, there is no observable compositional stratification across the batholith. The geochemical characteristics of the granitoids define three groups. Group 1 is characterized by strongly enriched incompatible elements and unfractionated middle rare earth elements (MREE)/heavy rare earth element patterns (HREE); Group 2 has enriched incompatible element concentrations similar to Group 1 but strongly fractionated MREE/HREE. Group 3 is characterized by only a limited incompatible element enrichment and unfractionated MREE/HREE. The origin of the different groups can be modeled through a relatively hydrous (Group 1 and 2) and of a less hydrous (Group 3) fractional crystallization line from a primitive basaltic parent at different pressures. Appropriate mafic/ultramafic cumulates that explain the chemical characteristics of each group are preserved at the base of the arc. The Kohistan batholith strengthens the conclusion that hydrous fractionation is the most important mechanism to form volumetrically significant amounts of granitoids in arcs. The Kohistan Group 2 granitoids have essentially identical trace element characteristics as Archean tonalite–trondhjemite–granodiorite (TTG) suites. Based on these observations, it is most likely that similar to the Group 2 rocks in the Kohistan arc, TTG gneisses were to a large part formed by hydrous high-pressure differentiation of primitive arc magmas in subduction zones. 相似文献
15.
在新疆北部准噶尔板块与阿尔泰造山带的缝合带即阿尔曼泰-扎河坝蛇绿混杂岩带附近,沿乌伦古河南岸分布一条碱性花岗岩带。它们形成的时代为292-309Ma,是阿尔泰地区海西期继同碰撞s型花岗岩类、碰撞后抬升Ⅰ型花岗岩类之后的最后一次岩浆活动的产物。这些碱性花岗岩以出现霓石、钠铁闪石、高硅、高碱、低钙、低镁、富集高场强元素为特征,属于典型的A型花岗岩。碱性花岗岩是海西期岩浆旋回的最后产物,活动时间很短暂,在空间上与蛇绿岩带伴生,为后造山A型碱性花岗岩(PA型),是阿尔泰海西期造山运动结束的重要标志。 相似文献
16.
In North Xinjiang there is an alkali granite belt extending in the NW-SE direction along the southern band of the Ulungur River and running parallel to the suture zone,i.e.,Aermantai-Zhaheba Ophiolitic Melange Zone ,between the Junggar Plate and the Altay Orogenic Belt.Whole -rock Rb-Sr isochron ages of the Ulungur alkali granites are within the range of 292-309Ma, showing that they were genetically connected with the latest episode of Hercynian magmatism subsequent to the syncollision S-type and post-collision uplifting I-type granitoids in the Altay region .The alkali granites are miner-alogically characterized by the occurrence of aegirine and arfvedsonite and chemically by high silicon and alkali,low calcium and magnesium and abundant high-field elements, being typical A-type granites .The alkali granites were formed in the final stage of the Hercynian calc-alkaline magmatic cycle in a very short period of time .They are in line with the post-orogenic A-type(PA-type)granites, implying that the tectonic regime was changed from compression to extension. 相似文献
17.
Santosh Kumar 《Journal of the Geological Society of India》2010,76(1):5-25
Felsic magmatisms in the north of Indus-Tsangpo Suture Zone (ITSZ) in Ladakh range of northwest Indian Himalaya, referred
herein Ladakh granitoids (LG), and associated magmatic rocks constitute the bulk of the Ladakh batholith. They have been characterized
as Andean-type, calc-alkaline, largely metaluminous (I-type) to a few peraluminous (S-type) granitoids derived from partial
melting of subducting materials. The LG can be broadly classified into coarsegrained facies with abundant mafics (hbl-bt),
medium-grained facies with low content of mafics, and fine-grained leucocratic facies with very low amount of mafics. Mesocratic
to melanocratic, rounded to elliptical, fine to medium grained, mafic to hybrid microgranular enclaves (ME) are ubiquitous
in medium to coarse-grained LG. ME are absent or rare in the leucocratic variety of LG. In this paper different types of ME,
and their field relation and microstructures with respect to felsic host LG are documented from northwestern, central, southeastern
parts of the Ladakh batholith. Rounded to elongate ME of variable sizes (a few cm to metres across, mostly d<30 cm) commonly
having sharp, crenulate, and occasionally diffuse contacts of ME with felsic host LG suggest that several pulses of crystal-charged
mafic and felsic magmas coexisted, hybridized, and co-mingled into subvolcanic settings. Occurrence of composite ME (several
small mafic ME enclosed into large porphyritic ME) strongly point to multiple mafic to hybrid magma intrusions into partly
crystalline LG magma chambers. Synplutonic mafic dykes disrupted to form subrounded to angular (brecciated) mafic ME swarms
commonly disposed in strike-length suggest mafic magma injections at waning stage of felsic magma evolution with large rheological
contrasts. Pillowing of mafic melt against leucocratic (aplitic) residual melt strongly suggests mafic magma intrusion in
nearly-crystallized condition of pluton. Although common mineral asemblages (hblbt-pl-kfs-qtz-ap-zrn-mt±ilm) of ME (diorite,
quartzdiorite) and host LG (granodiorite, monzogranite) may relate to their cogenetic relation, fine to medium grained porphyritic
(hybrid) nature and lack of cumulate texture of ME strongly oppose cognate origin for ME. Presence of plagioclase xenocrysts,
quartz ocelli and accicular apatite in porphyritic ME strongly indicate mingling and undercooling of hybridized ME globules
into relatively crystal-charged cooler host LG magma. Grain size differences of some ME, except to those of porphyritic ones,
appear related to varying degrees of undercooling of ME most likely controlled by their variable sizes. Several smaller ME,
however, lack fine-grained chilled margin probably because of their likely disaggregation from a large size ME during the
course of progressive hybridization (mingling to mixing) leaving behind trails of mafic schlieren. Field and microstructural
evidences at least suggest that Ladakh granitoids and their microgranular enclaves are products of multistage magma mingling
and mixing processes concomitant fractional differentiation of several batches of mafic and felsic magmas formed in open magma
chamber(s) of subduction setting. 相似文献
18.
Coronas and high-P veins in metagabbros of the Kohistan island arc, northern Pakistan: evidence for crustal thickening during cooling 总被引：2，自引：0，他引：2
Abstract The E-W-trending Kohistan terrane in the NW Himalaya is a sandwich of a magmatic arc between the collided Karakoram (Asian) and Indian plates. The southern part of the Kohistan arc is principally made up of amphibolites derived from volcanic and plutonic rocks of Early Cretaceous age. Gabbroic relics in the amphibolites display calc-alkaline character, and their mineralogy is similar to low-P plutonic rocks reported from modern and ancient island arcs. The largest of these relics, occurring along the southern margin of the amphibolite belt near Khwaza Khela, is subcircular in outline and is about 1 km across. It consists of cumulate gabbros and related rocks displaying a record of cooling and crustal thickening. Primary olivine and anorthite reacted to produce coronas consisting of two pyroxenes +Mg-Fe2+ -Al spinel ± tschermakitic hornblende at about 800° C, 5.5–7.5 kbar. This thermotectonic event is of regional extent and may be related to the overthrusting of the Karakoram plate onto the Kohistan arc some 85 Ma ago, or even earlier. Later the gabbros were locally traversed by veins containing high-P assemblages: garnet, kyanite, zoisite, paragonite, oligoclase, calcite, scapolite and quartz ° Chlorite ° Corundum ± diopside. Formed in the range 510–600° C, and 10–12 kbar, these suggest further thickening and cooling of the crust before its uplift during the Tertiary. This paper presents microprobe data on the minerals, and discusses the tectonic implications of the coronitic and vein assemblages in the gabbros. 相似文献
19.
新疆阿拉套山花岗岩类的岩石化学 总被引：6，自引：0，他引：6
新疆阿拉套山南坡东西向展布的花岗岩石的岩石化学研究表明，本区同时存在Ｉ型和Ｓ型两种类型的花岗岩，其分布受构造环境控制，靠近古板块缝合线为Ｉ型花岗岩分布区、远离古板块缝合线为Ｓ型花岗岩分布区。源岩性质和作用强弱等因素可能是造成岩石化学成分差异的原因。 相似文献
20.
北秦岭漂池岩体的源区特征及其形成的构造环境 总被引：12，自引：0，他引：12
北秦岭漂池花岗质岩基为早古生代岩浆活动的产物，岩石类型主要为二云母花岗岩。通过主要元素，微量元素及Ｎｄ，Ｓｒ，Ｏ同位素特征的分析，其成因类型为Ｓ型花岗岩，地物质来自壳源碎屑物，研究表明，秦岭群片麻岩类是形成漂池岩体的主要源岩，结合区域地质背景分析，岩体并不形成于板块碰撞环境，而形成北秦岭早古生代活动大陆边缘，受板块俯冲作用的动力学影响所诱发的陆缘地壳物质熔融的产物，因此，漂池岩体形成的构造类型是活 相似文献