Tectonic evolution of the South Altyn, NW China: constraints by geochemical, zircon U–Pb and Lu–Hf isotopic analysis of the Palaeozoic granitic plutons in the Mangya area

2020 ◽  
Vol 157 (7) ◽  
pp. 1121-1143
Author(s):  
Nan Xu ◽  
Cai-lai Wu ◽  
Yuan-Hong Gao ◽  
Min Lei ◽  
Kun Zheng ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Large Scale ◽  
Isotopic Analysis ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
The South ◽  
Nw China ◽  
Ophiolitic Mélange ◽  
High K ◽  
Continental Block

AbstractThe South Altyn Orogenic Belt (SAOB) is one of the most important orogenic belts in NW China, consisting of the South Altyn Continental Block and the Apa–Mangya Ophiolitic Mélange Belt. However, its Palaeozoic tectonic evolution is still controversial. Here, we present petrological, geochemical, zircon U–Pb and Lu–Hf isotopic data for the Mangya plutons with the aim of establishing the Palaeozoic tectonic evolution. We divide the Early Palaeozoic magmatism in the Apa–Mangya Ophiolitic Mélange Belt into four episodes and propose a plate tectonic model for the formation of these rocks. During 511–494 Ma, the South Altyn Ocean (SAO) was in a spreading stage, and some shoshonite series, I-type granitic rocks were generated. From 484 to 458 Ma, the oceanic crust of the SAO subducted northward, accompanied by large-scale magmatic events resulting in the generation of vast high-K calc-alkaline series, I-type granitic rocks. During 450–433 Ma, the SAO closed, and break-off of the subducted oceanic slab occurred, with the generation of some high-K calc-alkaline series, I–S transitional type granites. The SAOB was in post-orogenic extensional environment from 419 to 404 Ma, and many A-type granites were generated.

Igneous activity in central-southern Italy: Is the subduction paradigm still valid?

2022 ◽  
Author(s):  
Michele Lustrino ◽  
Claudio Chiarabba ◽  
Eugenio Carminati
Keyword(s):  
Large Scale ◽  
Oceanic Lithosphere ◽  
Tyrrhenian Sea ◽  
Calc Alkaline ◽  
Quaternary Volcanism ◽  
High K ◽  
Igneous Activity ◽  
Lateral Extent ◽  
Subduction System ◽  
Sea Area

ABSTRACT The Pliocene–Quaternary igneous record of the Tyrrhenian Sea area features a surprisingly large range of compositions from subalkaline to ultra-alkaline and from ultrabasic to acid. These rocks, emplaced within the basin and along its margins, are characterized by strongly SiO2-undersaturated and CaO-rich to strongly SiO2-oversaturated and peraluminous compositions, with sodic to ultrapotassic alkaline and tholeiitic to calc-alkaline and high-K calc-alkaline affinities. We focused on the different models proposed to explain the famous Roman Comagmatic Region, part of the Quaternary volcanism that spreads along the eastern side of the Tyrrhenian area, in the stretched part of the Apennines thrust-and-fold belt. We reviewed data and hypotheses proposed in the literature that infer active to fossil subduction up to models that exclude subduction entirely. Many field geology observations sustain the interpretation that the evolution of the Tyrrhenian-Apennine system was related to subduction of the western margin of Adria continental lithosphere after minor recycling of oceanic lithosphere. However, the lateral extent of the subducting slab in the last millions of years, when magmatism flared up, remains debatable. The igneous activity that developed in the last millions of years along the Tyrrhenian margin is here explained as originating from a subduction-modified mantle, regardless of whether the large-scale subduction system is still active.

Carbon isotope (δ13Ccarb) stratigraphy of the Early–Middle Ordovician (Tremadocian–Darriwilian) carbonate platform in the Tarim Basin, NW China: implications for global correlations

2020 ◽  
pp. 1-22 ◽  
Author(s):  
Xiaoqun Yang ◽  
Zhong Li ◽  
Tailiang Fan ◽  
Zhiqian Gao ◽  
Shuai Tang
Keyword(s):  
Sea Level ◽  
Carbon Isotope ◽  
Tarim Basin ◽  
Large Scale ◽  
Carbonate Platform ◽  
Sedimentary Environment ◽  
Isotopic Analysis ◽  
Nw China ◽  
Middle Ordovician ◽  
Positive Shift

Abstract Guided by conodont biostratigraphy and unconformities observed in the field, stable carbon isotopic analysis (δ13Ccarb) was performed on 210 samples from Lower–Middle Ordovician (Tremadocian to Darriwilian) sections and wells in the Tarim Basin, NW China. The δ13C trend in the Tarim Basin sections has three distinct characteristics: (1) from the Tremadocian to the Floian, a positive shift from −1.9 ‰ to −0.2 ‰ is observed near the boundary between the Penglaiba Formation and the Yingshan Formation; (2) from the Floian to the Dapingian, a positive shift in δ13C from −3 ‰ to −0.7 ‰ occurred under large-scale sea-level rise and a change in the sedimentary environment from a restricted platform to an open platform. Changes in the conodont type are also observed in the Tabei region; and (3) from the Dapingian to the Darriwilian, δ13C first decreased and then increased, showing a negative shift at the Dapingian–Darriwilian boundary. During the Floian, δ13C decreased in the study area, while it first decreased and then increased in other regions, which may reflect local sea-level movements in response to isostatic crustal movements. Two types of positive shift were identified at the Floian–Dapingian boundary, which likely show the effects of local factors, including a disconformity, dolomitization, and platform restriction, superimposed on the global signal of the carbon isotope. Some conodont zonations and recurrent negative excursions in Tremadocian, Floian and Dapingian stages appear to be truncated by unconformities, which are accompanied by short-term subaerial exposure due to sea-level fall and local tectonic uplift.

Geochemistry of the high-K calc-alkaline basaltic sills and dykes in the South Rhodope Massif (N Greece)

1984 ◽  
Vol 47 (3) ◽  
pp. 569-579 ◽  
Author(s):  
G. Eleftheriadis ◽  
G. Christofides ◽  
A. Kassoli-Fournaraki
Keyword(s):  
Calc Alkaline ◽  
The South ◽  
High K

scholarly journals Tectonic evolution and high-pressure rock exhumation in the Qiangtang Terrane, Central Tibet

2015 ◽  
Vol 7 (1) ◽  
pp. 329-367 ◽  
Author(s):  
Z. Zhao ◽  
P. D. Bons ◽  
G. Wang ◽  
A. Soesoo ◽  
Y. Liu
Keyword(s):  
High Pressure ◽  
Tectonic Evolution ◽  
Late Triassic ◽  
The South ◽  
Metamorphic Belt ◽  
The North ◽  
Ophiolitic Mélange ◽  
Basement Rocks ◽  
Central Tibet ◽  
Qiangtang Terrane

Abstract. Conflicting interpretations of the > 500 km long, east-west trending Qiangtang Metamorphic Belt have led to very different and contradicting models for the Permo-Triassic tectonic evolution of Central Tibet. We define two metamorphic events, one that only affected Pre-Ordovician basement rocks and one subduction-related Triassic high-pressure metamorphism event. Detailed mapping and structural analysis allowed us to define three main units that were juxtaposed due to collision of the North and South Qiangtang terranes after closure of the Ordovician-Triassic ocean that separated them. The base is formed by the Precambrian-Carboniferous basement, followed by non-metamorphic ophiolitic mélange, containing mafic rocks that range in age from the Ordovician to Middle Triassic. The top of the sequence is formed by strongly deformed sedimentary mélange that contains up to > 10 km size rafts of both un-metamorphosed Permian sediments and high-pressure blueschists. We propose that the high-pressure rocks were exhumed from underneath the South Qiangtang Terrane in an extensional setting caused by the pull of the northward subducting slab of the Shuanghu-Tethys. High-pressure rocks, sedimentary mélange and margin sediments were thrust on top of the ophiolitic mélange that was scraped off the subducting plate. Both units were subsequently thrust on top of the South Qiantang Terrane continental basement. Onset of Late Triassic sedimentation marked the end of the amalgamation of both Qiangtang terranes and the beginning of spreading between Qiantang and North Lhasa to the south, leading to the deposition of thick flysch deposits in the Jurassic.

scholarly journals Zircon U–Pb geochronology and geochemistry of granitic rocks in central Mongolia

2020 ◽  
Vol 50 ◽  
pp. 23-44
Author(s):  
Boldbaatar Dolzodmaa ◽  
Yasuhito Osanai ◽  
Nobuhiko Nakano ◽  
Tatsuro Adachi
Keyword(s):  
Tectonic Setting ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Central Mongolia ◽  
Central Asian ◽  
High K ◽  
Three Stages ◽  
Late Neoproterozoic

The Central Asian Orogenic Belt had been formed by amalgamation of voluminous subduction–accretionary complexes during the Late Neoproterozoic to the Mesozoic period. Mongolia is situated in the center of this belt. This study presents new zircon U–Pb geochronological, whole-rock major and trace element data for granitoids within central Mongolia and discusses the tectonic setting and evolution of these granitic magmas during their formation and emplacement. The zircon U–Pb ages indicate that the magmatism can be divided into three stages: the 564–532 Ma Baidrag granitoids, the 269–248 and 238–237 Ma Khangai granitoids. The 564–532 Ma Baidrag granitoids are adakitic, have an I-type affinity, and were emplaced into metamorphic rocks. In comparison, the 269–248 Ma granitoids have high-K, calc-alkaline, granodioritic compositions and are I-type granites, whereas the associated the 238–237 Ma granites have an A-type affinity. The 564–532 Ma Baidrag and 269–248 Ma Khangai granitoids also both have volcanic arc-type affinities, whereas the 238–237 Ma granites formed in a post-collisional tectonic setting. These geochronological and geochemical results suggest that arc magmatism occurred at the 564–532 Ma which might be the oldest magmatic activity in central Mongolia. Between the Baidrag and the Khangai, there might be paleo-ocean and the oceanic plate subducted beneath the Khangai and produced voluminous granite bodies during the 269–248 Ma. After the closure of the paleo-ocean, the post collisional granitoids were formed at the 238–237 Ma based on the result of later granitoids in the Khangai area.

scholarly journals Petrology and mineral chemistry of peraluminous Marziyan granites, Sanandaj-Sirjan metamorphic belt (NW Iran)

2015 ◽  
Vol 66 (5) ◽  
pp. 361-374 ◽  
Author(s):  
Esmaiel Darvishi ◽  
Mahmoud Khalili ◽  
Roy Beavers ◽  
Mohammad Sayari
Keyword(s):  
Mineral Chemistry ◽  
White Mica ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Metamorphic Belt ◽  
Nw Iran ◽  
The North ◽  
Continental Plate ◽  
High K ◽  
Type Granite

AbstractThe Marziyan granites are located in the north of Azna and crop out in the Sanandaj-Sirjan metamorphic belt. These rocks contain minerals such as quartz, K-feldspars, plagioclase, biotite, muscovite, garnet, tourmaline and minor sillimanite. The mineral chemistry of biotite indicates Fe-rich (siderophyllite), low TiO2, high Al2O3, and low MgO nature, suggesting considerable Al concentration in the source magma. These biotites crystallized from peraluminous S-type granite magma belonging to the ilmenite series. The white mica is rich in alumina and has muscovite composition. The peraluminous nature of these rocks is manifested by their remarkably high SiO2, Al2O3and high molar A/CNK (> 1.1) ratio. The latter feature is reflected by the presence of garnet and muscovite. All field observations, petrography, mineral chemistry and petrology evidence indicate a peraluminous, S-type nature of the Marziyan granitic rocks that formed by partial melting of metapelite rocks in the mid to upper crust possibly under vapour-absent conditions. These rocks display geochemical characteristics that span the medium to high-K and calc-alkaline nature and profound chemical features typical of syn-collisional magmatism during collision of the Afro-Arabian continental plate and the Central Iranian microplate.

Origin of Early Cretaceous high-K calc-alkaline granitoids, western Tibet: implications for the evolution of the Tethys in NW China

2013 ◽  
Vol 56 (1) ◽  
pp. 88-103 ◽  
Author(s):  
Yao-Hui Jiang ◽  
Zheng Liu ◽  
Ru-Ya Jia ◽  
Shi-Yong Liao ◽  
Peng Zhao ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Calc Alkaline ◽  
Nw China ◽  
High K

scholarly journals Geology and Mineralization of the Bald Hill Molybdenum Occurrence, Buller District, West Nelson, New Zealand

2021 ◽  
Author(s):  
◽  
Allan John Eggers
Keyword(s):  
Large Scale ◽  
Granitic Rocks ◽  
Calc Alkaline ◽  
Southeastern Australia ◽  
Lower Ordovician ◽  
Isotopic Analyses ◽  
Intrusive Rocks ◽  
Normative Quartz ◽  
Granite Batholith ◽  
High Level

<p>Molybdenite mineralization occurs within the Bald Hill Prospect (West Nelson) in brecciated and hornfelsed Greenland Group slates and metagreywackes and associated quartz trondhjemite porphyry minor intrusions (Lyell Porphyry). Potassium argon (K-Ar) ages of the Lyell Porphyry, several granites forming part of the adjacent Karamea Granite batholith (Bald Hill Granites) and mineralized hornfelsic country rocks fall in the range 102-120 Ma (mid-Cretaceous). Adjacent lower Ordovician Greenland Group slates yielded four K-Ar ages in the range 112-226 Ma indicating partial argon outgassing of these older metasediments. The Bald Hill Granites and the Lyell Porphyry granitic rocks belong to separate petrogenic provinces. Bald Hill Granites forming the western margin of the Karamea Granite batholith occur as a suite of foliated, medium-grained, muscovite-bearing leucogranites, pink microgranites and biotite-granites. Chemically these rocks are peraluminous-potash granites with 72-75% SiO2, MgONa2O with Rb > Sr and always contain more than 30% normative quartz and 3% normative corundum. In contrast, the Lyell Porphyry rocks intruding both Greenland Group and Bald Hill Granite country rocks, form a series of small, high-level plutons and cross-cutting dykes of quartz trondhjemite, granodiorite, quartz diorite, lamprophyre and quartz-bearing gabbroporphyry. Chemically the Lyell Porphyry intrusive rocks are soda-rich calc-alkaline granitoids containing 46-70% SiO2, >1% MgO, >2.2% CaO, with Na2O>K2O and Sr>Rb with less than 28% normative quartz and less than 2% normative corundum. From their studies of granite batholiths in southeastern Australia, Chappell and White (1974) recognise two contrasting granitoid types called I-type and S-type granites. The Lyell Porphyry and several other intrusive stocks associated with molybdenum mineralization in West Nelson and North Westland are shown to correspond to I-type granites, in contrast to the Karamea batholith granites (including Bald Hill Granites) which conform to S-type granites. Sulphur isotopic analyses of mineralization for ten molybdenum prospects in West Nelson indicate uniformly high temperatures of mineralization in the range 400° to 500°C, with a probable magmatic source for sulphur. The Bald Hill and other S-type granites forming the Karamea batholith were probably formed by the ultrametamorphism of crustal sedimentary material. The Lyell Porphyry and other molybdenum-bearing calc-alkaline intrusive stocks represent melt phases of deeper origin intruding the overlying granites and sediments. The emplacement of these stocks appears to equate with north-south lineaments and large scale circular features in the granite terranes of West Nelson. The geological setting, age, petrological characteristics and molybdenite mineralization of the Lyell Porphyry and Bald Hill Granites are similar to that of other West Nelson occurrences. All are associated with mid-Cretaceous minor granitic porphyry intrusions, emplaced in Paleozoic metasediments, close to the margins of the Karamea and Separation Point batholiths.</p>

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