scholarly journals Partial Melting of Subducted Sediments Produced Early Mesozoic Calc-alkaline Lamprophyres from Northern Guangxi Province, South China

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Hui-Min Su ◽  
Shao-Yong Jiang ◽  
Dong-Yang Zhang ◽  
Xiang-Ke Wu
Keyword(s):  
Partial Melting ◽  
South China ◽  
Guangxi Province ◽  
Calc Alkaline ◽  
Early Mesozoic ◽  
Alkaline Lamprophyres

Tectonic evolution of the Paleo-Tethys Ocean in Southwest Guangxi: evidence from acidic magmatic rocks in the Pingxiang area, SW China

2021 ◽  
Author(s):  
Wenmin Huang ◽  
Xijun Liu ◽  
Zhenglin Li ◽  
Bing Zhao ◽  
Yiying Han
Keyword(s):  
Partial Melting ◽  
South China ◽  
South China Block ◽  
Guangxi Province ◽  
The South ◽  
Crustal Rocks ◽  
The North ◽  
Early Mesozoic ◽  
Innovation Project ◽  
Tethys Ocean

<p>Early Mesozoic development of Southeast Asia involved oceanic subduction, closure, accretion and collision of discrete terranes rifted from Gondwana. South China, as an important continental terrane, is bound to the north by the Qinling-Dabie collisional orogenic belt, to the south by the Indochina Block, and to the east by the Pacific Plate. The role of continental collision and subduction during the Early Mesozoic development of South China has sparked the interest of geologists worldwide and stimulated considerable research. The Triassic tectonic history of the southwestern South China Block is marked by the Indosinian orogeny that records amalgamation of the Indochina and South China blocks during the late Permian to Triassic as a result of closure of the eastern branch of the Paleo-Tethys Ocean. In South China, there is widespread granitic magmatism, metamorphism and deformation. The closure of eastern Paleo-Tethys Ocean and subsequent collision between the South China block and Indochina Block has caused the collision zone metamorphism and formation of granites during the Permo-Triassic, with the Song Ma fault zone as the collision boundary. The Indosinian magmatism in the Pingxiang region was the magmatic products in this period. We report the new results of bulk-rock major and trace element, Nd, Hf isotopic compositions and zircon U–Pb dating of granites and rhyolites in the Pingxiang region in Guangxi Province, Southwest China, to decipher their petrogenesis and tectonic settings. The granites and rhyolitics in the Pingxiang area have low Mg<sup>#</sup> values (11.1–36.7), low Nb/Ta ratios (9.26–13.74) exhibiting a both affinity from S-type to I-type granaite. The isotopic features of these rocks show negative ε<sub>Hf</sub>(t) with the values ranging from -9.89 to -6.09, negative ε<sub>Nd</sub>(t) values ranging from -12.89 to -12.02 and T<sub>2DM</sub> values of 1.8–3.3 Ga, suggesting that the Pingxiang granites and rhyolites was derived from partial melting of paleoproterozoic crust rocks. The granites yielded <sup>206</sup>Pb/<sup>238</sup>U ages ranging from 243 to 241 Ma, and the rhyolites yielded <sup>206</sup>Pb/<sup>238</sup>U ages ranging from 247 to 245 Ma, which are both within the age range of the subduction to collision. Combine the regional geology, we suggest these granitoids and rhyolites were formed by the partial melting of crustal rocks during a transition from subduction to post-collisional environment with closure of Paleo-Tethys Ocean between the South China block and Indochina Block.</p><p>This study was financially supported by Guangxi Natural Science Foundation for Distinguished Young Scholars (2018GXNSFFA281009) and the Fifth Bagui Scholar Innovation Project of Guangxi Province (to XU Ji-feng).</p>

Late Paleozoic- Early Mesozoic tectonics of Hainan Island: Key to understanding Paleotethyan geology

2020 ◽  
Author(s):  
Huiying He ◽  
Peter Cawood ◽  
Yuejun Wang
Keyword(s):  
South China ◽  
Tectonic Evolution ◽  
Hainan Island ◽  
Igneous Rocks ◽  
Late Paleozoic ◽  
Calc Alkaline ◽  
Early Mesozoic ◽  
History Of ◽  
Back Arc ◽  
T Values

<p>In Southeast Asia, establishing the origin and associated tectonic setting of Late Paleozoic-Early Mesozoic igneous rocks is complicated by structural overprinting and the complex tectonic evolution of the Paleotethyan regime. Hainan Island, located at the south-eastern margin of the Paleotethys, and lacking significant tectonic overprints is a key to understand amalgamation history of the Indochina and South China blocks and to constraining the tectonic evolution of Paleotethys ocean in southeast Asia.</p><p>The Late Paleozoic-Early Mesozoic record of igneous rocks on Hainan Island includes the following. 1) ca. 350 Ma island arc andesites and ca. 330 Ma metabasites, the latter with both MORB- and arc-like geochemical affinities, positive ε<sub>Nd</sub>(t) values of +5.86 – +9.85 and rare inherited zircons with a zircon age of 1400 Ma inferred to be derived from a MORB source with the input of a slab-derived component. Together with the ~350 Ma island arc andesites, the Carboniferous tectonic environment is supposed to be a continental back-arc basin setting. 2) Late Permian gneiss granitoids (272-252 Ma) characterized by a gneissic foliation and calc-alkaline I-type geochemical affinities with negative Nb-Ta and Ti anomalies, related to metasomatized mantle wedge modified by the sediment-derived component in a continental arc setting. 3) ca. 257 Ma arc-like andesites, which further validate a subduction-related setting. 4) Peraluminious Early-Middle Triassic massive granitoids (251–243 Ma) with slightly high A/CNK ratios, δ<sup>18</sup>O values (up to 11.75 ‰) and Sr/Y ratios, inferred to have formed in a compressive regime from a mixed source of greywacke and metabasite. 5) Middle-Late Triassic (242–225 Ma) high-K calc-alkaline granitoids with high zircon temperatures (842–867°C) and geochemical signatures of A-type granites. They show slightly low whole-rock ε<sub>Nd</sub>(t) and zircon ε<sub>Hf</sub>(t) values, suggestive of the derivation from a metabasite–greywacke source in an extensional setting. 6) ca. 240 Ma gabbro-dolerites showing enrichment in LILEs, depletion in HFSEs, negative ε<sub>Nd</sub> (t)-ε<sub>Hf</sub> (t) values (−8.45 to −1.05 and −5.9 to −2.7, respectively) and crustal-like δ<sup>18</sup>O values (7.26–8.70‰), it is implied that the Hainan Island entered into post-collisional environment in response to the asthenosphere upwelling shortly after the closure of back-arc basin.</p><p>Thus, Hainan Island provides a record of Carboniferous back-arc basin opening, followed by an extended Permian–Triassic history of subduction-related consumption leading to orogenic assembly and extensional collapse between the South China and Indochina blocks. Such a tempo-spatial pattern is consistent with that along the Song Ma–Ailaoshan suture zone rather than the magmatic history of eastern South China and indicates that the Paleotethys extended west to at least Hainan Island in the Late Paleozoic-Early Mesozoic.</p>

Petrogenesis of the Early Palaeozoic granitoids from the Yunkai massif, South China block: implications for a tectonic transition from compression to extension during the Caledonian orogenic event

2017 ◽  
Vol 155 (8) ◽  
pp. 1776-1792 ◽  
Author(s):  
XIAO-FEI QIU ◽  
XIAO-MING ZHAO ◽  
HONG-MEI YANG ◽  
SHAN-SONG LU ◽  
TUO JIANG ◽  
...  
Keyword(s):  
Partial Melting ◽  
South China ◽  
Alkaline Rock ◽  
South China Block ◽  
Rock Series ◽  
Calc Alkaline ◽  
Tectonic Regime ◽  
Type Granite ◽  
Early Palaeozoic ◽  
T Values

AbstractA comprehensive geochronological and geochemical study was carried out on the gneissic monzogranites, porphyritic granodiorites and charnockites in the Gaozhou complex of the Yunkai massif in the southern part of the South China block to better understand the Early Palaeozoic tectonic regime of the South China block. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U–Pb dating of zircons indicates an age of 453.2 ± 5.1 Ma to the formation of the gneissic monzogranites, whereas the porphyritic granodiorites and charnockites were generated at 437.0 ± 1.5 Ma and 435.2 ± 2.2 Ma, respectively. The gneissic monzogranites show geochemical features consistent with the high-K, calc-alkaline rock series and are strongly peraluminous. They have SiO2contents ranging from 67.75 to 69.65 wt. % and relatively low CaO contents (1.66–1.94 wt. %). Their REE patterns are fractionated with enriched LREEs and negative Eu anomalies. The samples also show enrichment in LILEs (e.g. Rb and K) and Pb, and depletion in Sr, Ba and HFSEs (e.g. Nb, Ta, Ti and P). They haveεNd(t) values of −8.2 to −7.7. Conversely, the porphyritic granodiorites and charnockites are characterized as medium-K, calc-alkaline rock series and weakly to strongly peraluminous. They exhibit pronounced depletions in HFSEs and positive Pb anomalies. Compared to the earlier gneissic monzogranites, these rocks have relatively lower SiO2(65.50–69.36 wt. %), but higher CaO contents (3.34–4.05 wt. %), and have slightly lowerεNd(t) values (−9.1 to −8.4). Petrography and geochemical compositions of the gneissic monzogranites indicate that they are S-type granite and likely formed by partial melting of Neoproterozoic to Early Palaeozoic immature metagreywackes; whereas The porphyritic granodiorites and charnockites are A-type granite and likely derived from low degrees of partial melting of the dry, granulitic residue depleted by prior extraction of granitic melt. The new data for the Caledonian granitoids in the Yunkai massif suggest that they were formed in a post-collisional tectonic setting. They represent the earliest post-collisional alkaline magmatism reported so far in the Yunkai massif, and thus indicate a tectonic regime switch, from compression to extension, as early as the Late Ordovician to Early Silurian (~450–435 Ma).

scholarly journals Petrogenesis of a late-stage calc-alkaline granite in a giant S-type batholith: geochronology and Sr–Nd–Pb isotopes from the Nomatsaus granite (Donkerhoek batholith), Namibia

2021 ◽  
Author(s):  
S. Aspiotis ◽  
S. Jung ◽  
F. Hauff ◽  
R. L. Romer
Keyword(s):  
Partial Melting ◽  
Mineral Assemblage ◽  
Central Zone ◽  
Calc Alkaline ◽  
Pb Isotope ◽  
Alkaline Granite ◽  
Ti Oxides ◽  
Eu Anomaly ◽  
Environment Characteristic ◽  
Southern Central

AbstractThe late-tectonic 511.4 ± 0.6 Ma-old Nomatsaus intrusion (Donkerhoek batholith, Damara orogen, Namibia) consists of moderately peraluminous, magnesian, calc-alkalic to calcic granites similar to I-type granites worldwide. Major and trace-element variations and LREE and HREE concentrations in evolved rocks imply that the fractionated mineral assemblage includes biotite, Fe–Ti oxides, zircon, plagioclase and monazite. Increasing K2O abundance with increasing SiO2 suggests accumulation of K-feldspar; compatible with a small positive Eu anomaly in the most evolved rocks. In comparison with experimental data, the Nomatsaus granite was likely generated from meta-igneous sources of possibly dacitic composition that melted under water-undersaturated conditions (X H2O: 0.25–0.50) and at temperatures between 800 and 850 °C, compatible with the zircon and monazite saturation temperatures of 812 and 852 °C, respectively. The Nomatsaus granite has moderately radiogenic initial 87Sr/86Sr ratios (0.7067–0.7082), relatively radiogenic initial εNd values (− 2.9 to − 4.8) and moderately evolved Pb isotope ratios. Although initial Sr and Nd isotopic compositions of the granite do not vary with SiO2 or MgO contents, fSm/Nd and initial εNd values are negatively correlated indicating limited assimilation of crustal components during monazite-dominated fractional crystallization. The preferred petrogenetic model for the generation of the Nomatsaus granite involves a continent–continent collisional setting with stacking of crustal slices that in combination with high radioactive heat production rates heated the thickened crust, leading to the medium-P/high-T environment characteristic of the southern Central Zone of the Damara orogen. Such a setting promoted partial melting of metasedimentary sources during the initial stages of crustal heating, followed by the partial melting of meta-igneous rocks at mid-crustal levels at higher P–T conditions and relatively late in the orogenic evolution.

scholarly journals Phylogenetic model of <i>Follicucullus</i> lineages (Albaillellaria, Radiolaria) based on high-resolution biostratigraphy of the Permian Bancheng Formation, Guangxi, South China

2014 ◽  
Vol 33 (2) ◽  
pp. 179-192 ◽  
Author(s):  
Lei Zhang ◽  
Tsuyoshi Ito ◽  
Qinglai Feng ◽  
Martial Caridroit ◽  
Taniel Danelian
Keyword(s):  
High Resolution ◽  
South China ◽  
Guangxi Province ◽  
Phylogenetic Model ◽  
Stratigraphic Ranges ◽  
Abundant Genus ◽  
Radiolarian Assemblages

Abstract. High-resolution sampling was performed on four Permian sections in Guangxi Province, South China (Gujingling, Sanpaoling, Guoyuan and Yutouling sections). We report abundant and well-preserved Guadalupian–Lopingian radiolarian assemblages, with 25 species belonging to three genera of the order Albaillellaria. Among them, the most abundant genus is Follicucullus with 17 species: F. bipartitus, F. charveti, F. sp. cf. F. charveti, F. dilatatus, F. falx, F. sp. cf. F. falx, F. guangxiensis, F. hamatus, F. monacanthus, F. sp. cf. F. monacanthus, F. orthogonus, F. sp. cf. F. orthogonus, F. porrectus, F. scholasticus, F. sp. cf. F. scholasticus, F. ventricosus and F. sp. cf. F. ventricosus. On the basis of composite stratigraphic ranges, this study suggests four Interval Zones in ascending order, namely F. monacanthus, F. porrectus, F. scholasticus and F. charveti Interval Zones. We provide a phylogenetic model for Follicucullus based on their morphological affinities and stratigraphic distribution. The genus Follicucullus originated from Pseudoalbaillella fusiformis, with F. monacanthus as the forerunner species from which two contemporary species then radiated: F. dilatatus and F. porrectus. Follicucullus porrectus is a long-lasting species, it is abundant in our material and several Follicucullus lineages originated from it. In terms of evolution it is considered to be the ancestor of a number of Follicucullus species.

Dynamic patterns of latest Proterozoic-Palaeozoic-early Mesozoic marine biodiversity in South China

2007 ◽  
Vol 42 (3-4) ◽  
pp. 431-454 ◽  
Author(s):  
Rong Jiayu ◽  
Fan Junxuan ◽  
Arnold I. Miller ◽  
Li Guoxiang
Keyword(s):  
South China ◽  
Marine Biodiversity ◽  
Early Mesozoic ◽  
Dynamic Patterns

Geochemistry and Sr–Nd isotopic composition of Eocene lamphrophyre dykes, southeastern British Columbia

2003 ◽  
Vol 40 (6) ◽  
pp. 853-864 ◽  
Author(s):  
J H Sevigny ◽  
R J Thériault
Keyword(s):  
British Columbia ◽  
Limited Range ◽  
Calc Alkaline ◽  
Lithospheric Thinning ◽  
Enriched Mantle ◽  
Mantle Enrichment ◽  
Mantle Reservoir ◽  
Geochemical Analyses ◽  
Alkaline Lamprophyres

Mineral compositions, geochemical analyses, and Sr–Nd isotopic compositions are reported for alkaline and calc-alkaline lamprophyres collected along the southern margin of the Valhalla Complex, southeastern British Columbia. The lamprophyres were emplaced during Eocene extension and lithospheric thinning associated with tectonic denudation of the Valhalla Complex. SiO2 contents range from 44.4–51.6 wt.%, K2O from 1.3–3.7 wt.%, and volatile contents (H2O + CO2 + SO3) from 0.8–4.6 wt.%. MgO and Cr contents are 9.5–7.6 wt.% and 540–130 ppm, respectively, for samples with Mg#s between 0.69 and 0.65. Chrondrite-normalized rare-earth element patterns are strongly fractionated with Cen = 120–375 and Ybn = 8.4–12.7. Alkaline lamprophyres contain biotite ± kaersutite ± calcic plagioclase and exhibit a limited range in initial 87Sr/86Sr (0.7051–0.7057), initial εNd (–3.7 to –4.3), and TDM (766–796 Ma). Calc-alkaline lamprophyres contain F-rich phlogopite and sodic plagioclase, and exhibit a wider range in initial 87Sr/86Sr (0.7064–0.7090), initial εNd (–6.3 to –11.9), and TDM (917–1,614 Ma). Alkaline lamprophyres are interpreted as uncontaminated melts derived from a long-term, volatile, and incompatible element-enriched mantle reservoir. Mantle enrichment coincided with continental rifting of western North America (ca. 760 Ma). The enriched mantle reservoir remained isolated for ~700 Ma. Lamprophyres were generated by partial melting of the mantle reservoir in response to adiabatic decompression and lithospheric thinning during Eocene extension.

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