Overlapping Sr–Nd–Hf–O isotopic compositions in Permian mafic enclaves and host granitoids in Alxa Block, NW China: Evidence for crust–mantle interaction and implications for the generation of silicic igneous provinces

Wei, Dan; Wang, Qiang; Wang, Xuan‐Ce; Liu, Yü; Wyman, Derek A.; Liu, Yongsheng

doi:10.1016/j.lithos.2015.05.016

Cited by 51 publications

(23 citation statements)

References 91 publications

(122 reference statements)

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“…Therefore, an episode of magmatism between 280 and 268 Ma took place in the Alxa Terrane, characterized by varied granitoids including quartz diorite, granodiorite, monzogranite, and syenogranite. This is consistent with previous studies that suggested a Permian magmatic event in the Alxa Terrane (e.g., Dan et al, 2014aDan et al, , 2015bLiu et al, 2016). Apart from the predominant granitoids, some 280-264 Ma ultramafic to intermediate magmatic rocks were also unveiled in the eastern part of the NLB and the middle part of the SLB L.…”

Section: Permian To Triassic Magmatic Episodes In the Alxa Terranesupporting

confidence: 92%

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

et al. 2017

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As a pivotal junction between the North China and Tarim cratons, the Alxa Terrane provides an ideal window to constrain the final closure of the middle segment of the Paleo-Asian Ocean (PAO). This study carried out petrological, whole-rock geochemical, and zircon U-Pb-Hf isotopic investigations on four major granitic plutonic complexes in the Alxa Terrane. The Bayan Nuru and Yabulai plutonic complexes are I-type granitoids that yield crystallization ages of 281-268 Ma and 277-270 Ma, respectively, with negative zircon ε Hf (t) values (−11.5 to −3.2), primarily sourced from the Neoproterozoic rocks in the region. The Nuergai granitoids yield crystallization ages of 281-268 Ma and show I-type affinities and positive zircon ε Hf (t) values (+1.6 to +6.4), indicating an origin related to magma mixing. Emplaced at ca. 241 Ma, the Oliji granitoids display varying zircon ε Hf (t) values from −0.9 to +11.5, which necessitate a predominant source of mantle-derived materials. A compilation of zircon ε Hf (t) and whole-rock ε Nd (t) values of the magmatic rocks in the Alxa Terrane illustrates a decreasing trend from the Late Carboniferous to the Early Permian and an increasing trend during Middle Permian to Triassic time. The marked shift with a large variation of zircon ε Hf (t) and whole-rock ε Nd (t) values at 280-265 Ma indicates a tectonic switch from subduction to post-collision tectonic regimes in the Alxa Terrane, marking the final closure of the middle segment of the PAO. Comparable isotope variations are also identified from 260 to 245 Ma magmatic counterparts on the northern margin of the North China Craton, hence suggesting a progressively eastward closure of the PAO.

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Section: Permian To Triassic Magmatic Episodes In the Alxa Terranesupporting

confidence: 92%

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

et al. 2017

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“…Large volumes of granitoids intruding into the metamorphic rocks have ages ranging from Late Silurian to Middle‐Late Triassic (Z. Z. Wang et al, ), with most of them clustering in a relatively short period (circa 290–270 Ma, Dan, Li, Wang, Tang, et al, ; Dan et al, ; Geng & Zhou, ; Q. Liu, Zhao, Han, Eizenhofer, Zhu, Hou, & Zhang, ; Q. Liu, Zhao, Han, Eizenhofer, Zhu, Hou, Zhang, & Wang, ; Zhang et al, ). In the northern part of the Nuru‐Langshan Tectonic Zone, ultramafic‐mafic rocks occur, hosted in Precambrian gneisses in the Bijiertai, Honggueryulin, and Diebusige areas.…”

Section: Regional Tectonicsmentioning

confidence: 99%

Final Subduction Processes of the Paleo‐Asian Ocean in the Alxa Tectonic Belt (NW China): Constraints From Field and Chronological Data of Permian Arc‐Related Volcano‐Sedimentary Rocks

et al. 2018

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The timing of final subduction and closure of the Paleo-Asian Ocean (PAO) is controversial.Located in a key position within the southern Central Asian Orogenic Belt, the Alxa Tectonic Belt (ATB) provides a crucial window to evaluate the final subduction processes of the PAO. This study presents field and geochronological data for Permian volcano-sedimentary rocks from the southwestern ATB. Field observations revealed a syntectonic unconformity between the Middle and Upper Permian strata. Detrital zircon U-Pb analyses show a major peak at~273 Ma and a subordinate peak at~440 Ma for the Middle Permian sample. The Upper Permian samples show consistently unimodal age spectra with single peaks at 261 and~263 Ma, respectively. The Permian zircons from the analyzed samples yield predominately positive ε Hf (t) values, indicating major juvenile magmatic processes mixed with limited recycled Precambrian basement. The diagnostic zircon U-Pb-Hf isotopic characteristics and ubiquitous intermediate and felsic volcanic detritus in these rocks indicate rapid sediments accumulation sourced from a proximal magmatic terrane in a suprasubduction zone environment. The Paleozoic zircon U-Pb age peaks from this study are comparable to those for the Permian arc-related sediments along the Solonker Suture Zone, thus linking the Alxa active margin with the northern margin of the North China Craton during Middle-Late Permian times. Our study thus provides key constraints for the final subduction processes of the PAO, documented within the ATB, before the terminal amalgamation of the southern Central Asian Orogenic Belt.

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“…The cognate origin model for crystallization of the MMEs from a coeval magma that gave rise to the host granitoids accounts for similar mineral assemblage and similarities in chemical and isotopic compo- sitions between enclaves and their hosts (e.g., Borodina, 1977, 1991;Dodge and Kistler, 1990;Pin et al, 1990;Dorais et al, 1997;Dahlquist, 2002;Donaire et al, 2005;Ilbeyli and Pearce, 2005;Chen et al, 2007;Shellnutt et al, 2010;Esna-Ashari et al, 2011;Flood and Shaw, 2014). In hybridism or magma mixing and/or mingling model for origin of the MMEs within the granitic pluton, the mineral, chemical, and isotopic similarities between enclaves and their hosts are commonly interpreted in terms of complete thermal and chemical equilibration between coeval, compositionally contrasted magmas in a slowly cooling plutonic body (e.g., Holden et al, 1991;Barbarin and Didier, 1992;van der Laan and Wyllie, 1993;Barbarin, 2005;Kaygusuz and Aydınçakır, 2009;Xiong et al, 2012;Zi et al, 2012;Dan et al, 2015;Ghaffari and Rashidnejad-Omran, 2015). However, others interpreted these similarities as evidence for cognate origin of the MMEs from a coeval magma that gave rise to the host granitoids (e.g., Borodina, 1977, 1991;Dodge and Kistler, 1990;Pin et al, 1990;Dorais et al, 1997;Dahlquist, 2002;Donaire et al, 2005;Ilbeyli and Pearce, 2005;Chen et al, 2007;Shellnutt et al, 2010;Esna-Ashari et al, 2011;Niu et al, 2013;Flood and Shaw, 2014;Huang et al, 2014;…”

Section: Implications For Origin Of the Mmes In Calc-alkaline Granitoidsmentioning

confidence: 99%

“…Several models have been proposed for the ori gin of MMEs in granitic rocks: (1) a hybrid or magma mixing and/or mingling model arguing that MMEs represent extraneous mafic magma blobs likely produced from the mantle that have mingled or partly mixed with felsic magmas derived from the crust or felsic magmas derived by fractional crystallization (e.g., Didier, 1973;Reid et al, 1983;Vernon, 1983Vernon, , 1984Vernon, , 1990Vernon, , 2014Cantagrel et al, 1984;Eberz and Nicholls, 1988;Vernon et al, 1988; Barbarin, 1990;Castro et al, 1990aCastro et al, , 1990bDorais et al, 1990;Fourcade and Javoy, 1991;Holden et al, 1991;Orsini et al, 1991;Poli and Tommasini, 1991;Elburg and Nicholls, 1995;Stimac et al, 1995;Elburg, 1996aElburg, , 1996bMaas et al, 1997;Collins et al, 2000;Ratajeski et al, 2001;Perugini et al, 2003;Tepper and Kuehner, 2004;Ilbeyli and Pearce, 2005;Kocak, 2006;Chen et al, 2009a;Qin et al, 2010;Sun et al, 2010;Perugini and Poli, 2012;Xiong et al, 2012;Zi et al, 2012;Clemens and Elburg, 2013;Dan et al, 2015); (2) a restitic origin model interpreted the enclaves as refractory pods of the source rock of the granitoid (e.g., White and Chappell, 1977;…”

Section: Introductionmentioning

confidence: 99%

Cogenetic origin of mafic microgranular enclaves in calc-alkaline granitoids: The Permian plutons in the northern North China Block

Zhang

Zhao

2017

Geosphere

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Mafic microgranular (microgranitoid) enclaves (MMEs) with fineto medium-grain-size igneous microstructures are abundant in Permian gran itoid plutons in the northern North China Block (NCB). They are mainly dioritic in composition with SiO 2 contents from 51.0 wt% to 62.7 wt% and are contiguous with their host granitoids (SiO 2 = 60.4-68.4 wt%). Their main mineral assemblage of plagioclase (oligoclase and andesine), hornblende, biotite, K-feldspar, and quartz is similar to that of their host granitoids but with different mineral proportions. Zircon laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb dating, hornblende-plagioclase thermobarometry, and Ti-in-zircon thermometry results show that the crystallization ages and pressure-temperature (P-T) conditions of the MMEs in each Permian granitoid pluton are very similar to those of their host granitoids, indicating simultaneous crystallization at the middle to upper crustal levels. Petrographical, geochemical, and Sr-Nd-Hf isotopic data show that the source areas of the Permian granitoid plutons in the northern NCB are temporally and spatially different and magma mixing was likely involved during formation of some granitoid plutons. However, the whole-rock Sr-Nd and zircon Hf isotopic compositions of the MMEs in each pluton are very similar to those of their host granitoids, indicating complete isotopic equilibration between the host granitoids and their enclaves. Combined with similar mineral assemblage and mineral chemistry between the MMEs and their host granitoids and absence of coeval mantle-derived rocks in or nearby the plutons, we confirm that the MMEs were crystallized from a coeval magma that gave rise to the host granitoids, and not by mixing and/or mingling between mantle-derived mafic and crustal-derived felsic magmas or by synplutonic injections of mafic magma into the host granitoid magma. We conclude that magma isotopic equilibration between host granitoids and their enclaves was achieved prior to emplacement and the magma mixing process during formation of some Permian granitoid plutons occurred mainly in the melting, assimilation, storage, and homogenization (MASH) zone in the lowermost crust or mantle-crust transition, not in the magma conduits or chambers at middle to upper crustal levels. A two-stage model that includes rapid cooling within the cogenetic host granitoid magma operating at pluton margins to form solid to sub-solid dioritic rocks and crystal accumulations of the host granitoid magma at the bottom of the pluton to form cumulates, and dioritic rocks and cumulates then fragmentated and interacted with progressive evolved host granitoid magma to change their shapes and orientations is proposed for origin of the MMEs in the Permian granitoid plutons in the northern NCB. This model may be more widely applicable to the generation of many MMEs in granitic rocks, especially where no direct evidence exists for the presence of mafic magmas coeval with granitoids and where there is a lack of isotopic contrast between...

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Overlapping Sr–Nd–Hf–O isotopic compositions in Permian mafic enclaves and host granitoids in Alxa Block, NW China: Evidence for crust–mantle interaction and implications for the generation of silicic igneous provinces

Cited by 51 publications

References 91 publications

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

Final Subduction Processes of the Paleo‐Asian Ocean in the Alxa Tectonic Belt (NW China): Constraints From Field and Chronological Data of Permian Arc‐Related Volcano‐Sedimentary Rocks

Cogenetic origin of mafic microgranular enclaves in calc-alkaline granitoids: The Permian plutons in the northern North China Block

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