scholarly journals Protracted Storage for Calc-Alkaline Andesitic Magma in Magma Chambers: Perspective from the Nageng Andesite, East Kunlun Orogen, NW China

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 198
Author(s):  
Xiao-Dong Chen ◽  
Bin Li ◽  
Chong-Bo Sun ◽  
Hong-Bing Zhou
Keyword(s):  
Magma Chamber ◽  
Basaltic Andesite ◽  
Magma Source ◽  
Calc Alkaline ◽  
Magma Chambers ◽  
Pb Isotope ◽  
Zircon Core ◽  
Nw China ◽  
East Kunlun ◽  
T Values

Calc-alkaline andesitic rocks are a major product of subduction-related magmatism at convergent margins. Where these melts are originated, how long they are stored in the magma chambers, and how they evolved is still a matter of debate. In this study, we present new data of whole-rock elemental and Sr-Nd-Pb isotope compositions, and zircon U-Pb-Th isotopes and trace element contents of Nageng (basaltic-)andesites in the East Kunlun Orogen (NW China). The similar age and whole-rock elemental and Sr-Nd-Pb isotope contents suggest that the Nageng andesite and basaltic andesite are co-magmatic. Their low initial 87Sr/86Sr (0.7084–0.7086) but negative εNd(t) values (−10.61 to −9.49) are consistent with a magma source from the juvenile mafic lower crust, possibly related to the mantle wedge with recycled sediment input. The U-Pb age gap between the zircon core (ca. 248 Ma) and rim (ca. 240 Ma) reveals a protracted magma storage (~8 Myr) prior to the volcanic eruption. When compared to the zircon rims, the zircon cores have higher Ti content and Zr/Hf and Nb/Ta ratios, but lower Hf content and light/heavy rare earth element ratios, which suggests that the parental magma was hotter and less evolved than the basaltic andesite. The plagioclase accumulation likely resulted in Al2O3-enrichment and Fe-depletion, forming the calc-alkaline signature of the Nageng (basaltic-)andesites. The magma temperature, as indicated by the zircon saturation and Ti-in-zircon thermometry, remained low (725–828 °C), and allowed for the magma chamber to survive over ~8 Myr. The decreasing εHf(t) values from zircon core (avg. 0.21, range: −1.28 to 1.32) to rim (avg. −3.68, range: −7.30 to −1.13), together with the presence of some very old xenocrystic zircons (268–856 Ma), suggest that the magma chamber had undergone extensive crustal contamination.

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.

Collision and reactivation along the South Tianshan Orogen (NW China) through late Paleozoic to Mesozoic time

2021 ◽  
Author(s):  
Yigui Han ◽  
Guochun Zhao
Keyword(s):  
Continental Collision ◽  
Orogenic Belt ◽  
Late Paleozoic ◽  
Magma Source ◽  
The South ◽  
Nw China ◽  
Magmatic Rocks ◽  
Western Tianshan ◽  
Tarim Craton ◽  
South Tianshan

<p>The South Tianshan Orogenic Belt in NW China marks the suturing site between the Tarim Craton and the Central Asian Orogenic Belt (CAOB) during late Paleozoic-Mesozoic time. Despite numerous investigations, the amalgamation history along the South Tianshan Orogen remains controversial, especially on the timing and process of the final continental collision between the Tarim Craton and the Central Tianshan (CTS)-Yili Block. We inquire into this issue on the basis of a compiled dataset across the Tarim, South Tianshan and CTS-Yili regions, comprising elemental and isotopic data of magmatic rocks and radiometric ages of regional magmatism, detrital zircons, (ultra-)high pressure metamorphism and tectonothermal events. The data support a continental collision along the South Tianshan belt in 310-300 Ma, in accord with a contemporaneous magmatic quiescence and a prominent decrease of εNd(t) and εHf(t) values of magmatic rocks in the CTS region, and a main exhumation stage of (U)HP rocks in the South Tianshan region. The collisional orogeny along the South Tianshan have most likely been influenced by a mantle plume initiated at ca. 300 Ma underneath the northern Tarim Craton, as evidenced by temporal and spatial variations of geochemical proxies tracing magma source characteristics. The new model of plume-modified collision orogeny reconciles the absence of continental-type (U)HP rocks in the orogen and the insignificant upper-plate uplift during continental collision. In the mid-Triassic (ca. 240 Ma), the Chinese western Tianshan underwent intense surface uplift and denudation, as indicated by sedimentary provenance analysis and tectonothermal events. Paleocurrent and detrital zircon age data from Triassic strata in northern Tarim suggest a provenance change from a single source of the Tarim Craton to multiple sources including the CTS-Yili Block to the north and the Western Kunlun Orogen to the south. We suggest that the mid-Triassic uplifting in Chinese western Tianshan was an intracontinental orogeny caused by far-field effects of the collision between the Tarim Craton and the Qiangtang Block. This research was financially supported by NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).</p>

scholarly journals Petrogenesis of the synplutonic high-magnesian porphyritic dykes from the mafic-granitoid plutons of the East-European Craton, Voronezh crystalline massif

2019 ◽  
Vol 64 (4) ◽  
pp. 356-371
Author(s):  
R. A. Terentiev
Keyword(s):  
Trace Elements ◽  
Magma Chamber ◽  
Earth Element ◽  
Parent Magma ◽  
Chrome Spinel ◽  
Calc Alkaline ◽  
East European ◽  
Fine Grained ◽  
Mineral Inclusions ◽  
Metasomatized Mantle

This paper documents the data on high-Mg porphyrite dykes (PDs) from the mafic to felsic (~2.09 Ma) plutons of Elan complex (EC). The low-thickness (first centimeters) synplutonic dykes are characterized by sharp straight contacts without visible chilling zones, in contrast to the larger (up to 119 m) dykes that have gradual transitions. The dykes are fresh, porphyritic (bronzite, Al-enstatite, labradorite) and has fine-grained mainly quartzo-feldspathic (+biotite, sulfides, accessories, ±hypersthene) matrix. Based on geochemistry data the PDs are intermediate rocks (SiO2 = 58.9–60.3 wt. %) and plot into calc-alkaline series with high magnesian of whole rock (Mg# ~0.7) and felsic (68.9–70.2 wt. %) matrix (Mg# ~0.5). The PDs show differentiated rare-earth element patterns with negligible Eu anomalies. The bronzite phenocrysts varying sizes are characterized by block zoning and contain irregular inclusions of olivine (Mg# ~0.85), clinopyroxene (Mg# ~0.88), phlogopite (Mg# up to 0.94), labradorite, chrome spinel, graphite and sulfides. The Al-enstatite phenocrysts are practically sterile with respect to trace elements and mineral inclusions. The geochemical features as well as diffusion zones, reaction rims, and resorbed faces of the phenocrysts such as orthopyroxene and plagioclase indicate processes of recrystallization and/or partial dissolution of nonequilibrium crystals in the melt and indicate intratelluric nature of the dyke phenocrysts that cores are inherited from the EC derivatives/cumulate. The mineral thermometry estimates are: (1) the parent magma starting temperatures of 1200–1400 °С and (2) the EC crystallization temperatures 1080–1155 °С, (3) the PD emplacement temperatures 910–1070 °С. The petrogenetic model supposes the generation of EC high-temperature magmas similar to boninites from an upper metasomatized mantle. The melt is contaminated with continental crust lithologies. It implies the half-way evolved magma chamber in the crust. The PD melt, as a result of ending of the half-way magma chamber evolution, was emplaced into the still unheated EC plutons.

scholarly journals Genesis of the volcanic-related Be-U-Mo Baiyanghe deposit, West Junggar (NW China), constrained by mineralogical, trace element and U-Pb isotope signatures of the primary U mineralisation

2021 ◽  
Vol 128 ◽  
pp. 103921
Author(s):  
Christophe Bonnetti ◽  
Xiaodong Liu ◽  
Julien Mercadier ◽  
Michel Cuney ◽  
Bin Wu ◽  
...  
Keyword(s):  
Trace Element ◽  
Pb Isotope ◽  
Nw China ◽  
West Junggar

scholarly journals Geochronological and Geochemical Constraints on the Origin of the Hutouya Polymetallic Skarn Deposit in the East Kunlun Orogenic Belt, NW China

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1136
Author(s):  
Hongchang Gao ◽  
Fengyue Sun ◽  
Bile Li ◽  
Ye Qian ◽  
Li Wang ◽  
...  
Keyword(s):  
Lower Crust ◽  
Inductively Coupled Plasma ◽  
Orogenic Belt ◽  
Granitic Rocks ◽  
Skarn Deposit ◽  
Nw China ◽  
Inductively Coupled ◽  
East Kunlun ◽  
Ore Minerals ◽  
East Kunlun Orogenic Belt

The Hutouya polymetallic skarn deposit lies in the Qimantagh area of the East Kunlun Orogenic Belt, NW China. Skarnization and mineralization at the deposit are closely associated with contemporary felsic intrusions. In this paper, zircon U-Pb ages and zircon Hf isotope as well as whole-rock geochemical and whole-rock Sr-Nd isotope data are reported for intrusive rocks and crystal tuff of the Elashan Formation in the Hutouya area. Moreover, Re-Os ages and S-Pb isotopes are also reported for the ore minerals in the Hutouya deposit. The Zircon laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U-Pb age of granodiorite and Re-Os isochron age of molybdenite suggest that mineralizations occurred at ca. 227 Ma and that the granodiorite and molybdenite are closely related petrogenetically. All the granitoids in the Hutouya deposit are high-K calc-alkaline and metaluminous to weakly peraluminous I-type granitoids. Among them, the ore-forming granitoids were derived by the mixing of crust-derived (either juvenile or ancient mature lower crust) and mantle-derived magmas, whereas the non-ore-related granite porphyry was generated by the partial melting of a single ancient mature lower crust. The magmas of all the granitoids underwent extensive fractionation–crystallization during the process of rising and emplacement. The sulfur of the analyzed samples from the northern and middle zone of Hutouya deposit (including No. II, III, IV, and VI ore belts) belongs to deep magmatic sulfur, while the sulfur of samples from the southern zone of Hutouya deposit (No. VII ore belt) includes not only deep magmatic sulfur but also a contribution of strata sulfur. All the ore mineral samples in the Hutouya deposit have similar Pb compositions that are consistently derived from a mixed source of upper crust and mantle. Tectonic discrimination diagrams indicate a post-collisional setting for all granitic rocks of the Hutouya skarn deposit, which is therefore considered a product of a the post-collision extensional system and is consistent with other porphyry-skarn deposits within the East Kunlun Orogenic Belt.

Oxygen-Hafnium-Neodymium Isotope Constraints on the Origin of the Talnakh Ultramafic-Mafic Intrusion (Norilsk Province, Russia)

2020 ◽  
Vol 115 (6) ◽  
pp. 1195-1212 ◽  
Author(s):  
Kreshimir N. Malitch ◽  
Elena A. Belousova ◽  
William L. Griffin ◽  
Laure Martin ◽  
Inna Yu. Badanina ◽  
...  
Keyword(s):  
Crustal Contamination ◽  
Ultramafic Rocks ◽  
Magma Chambers ◽  
Nd Isotope ◽  
Crustal Component ◽  
Depleted Mantle ◽  
Magma Sources ◽  
A Minor ◽  
T Values

Abstract The ultramafic-mafic Talnakh intrusion in the Norilsk province (Russia) hosts one of the world’s major platinum group element (PGE)-Cu-Ni sulfide deposits. This study employed a multitechnique approach, including in situ Hf-O isotope analyses of zircon combined with whole-rock Nd isotope data, in order to gain new insights into genesis of the Talnakh economic intrusion. Zircons from gabbrodiorite, gabbroic rocks of the layered series, and ultramafic rocks have similar mantle-like mean δ18O values (5.39 ± 0.49‰, n = 27; 5.64 ± 0.48‰, n = 34; and 5.28 ± 0.34‰, n = 7, respectively), consistent with a mantle-derived origin for the primary magma(s) parental to the Talnakh intrusion. In contrast, a sulfide-bearing taxitic-textured troctolite from the basal part of intrusion has high δ18O (mean of 6.50‰, n = 3), indicating the possible involvement of a crustal component during the formation of sulfide-bearing taxitic-textured rocks. The Hf isotope compositions of zircon from different rocks of the Talnakh intrusion show significant variations, with ɛHf(t) values ranging from –3.2 to 9.8 for gabbrodiorite, from –4.3 to 11.6 for unmineralized layered-sequence gabbroic rocks, from 2.3 to 12 for mineralized ultramafic rocks, and from –3.5 to 8.8 for mineralized taxitic-textured rocks at the base of the intrusion. The significant range in the initial 176Hf/177Hf values is ascribed to interaction of distinct magma sources during formation of the Talnakh intrusion. These include (1) a juvenile source equivalent to the depleted mantle, (2) a subcontinental lithospheric source, and (3) a minor crustal component. Initial whole-rock Nd isotope compositions of the mineralized taxitic-textured rocks from the base of the intrusion (mean ɛNd(t) = –1.5 ± 1.8) differ from the other rocks, which have relatively restricted ranges in initial ɛNd (mean ɛNd = 0.9 ± 0.2). The major set of ɛNd values around 1.0 at Talnakh is attributed to limited crustal contamination, presumably in deep magma chambers, whereas the smaller set of negative ɛNd values in taxitic-textured rocks is consistent with greater involvement of a crustal component and reflects an interaction with the wall rocks during emplacement.

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