Syn-collisional felsic magmatism and continental crust growth: A case study from the North Qilian Orogenic Belt at the northern margin of the Tibetan Plateau

Chen, Shuo; Niu, Yaoling; Xue, Q. K.

doi:10.1016/j.lithos.2018.03.001

Cited by 24 publications

(41 citation statements)

References 77 publications

(100 reference statements)

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“…In addition, collision-related (syncollisional or post-collisional) magmatic rocks with juvenile isotopic signatures have been reported from this orogen (Song et al, 2015;S. Chen et al, 2016bS. Chen et al, , 2018.…”

Section: Introductionmentioning

confidence: 80%

Early Paleozoic collision-related magmatism in the eastern North Qilian orogen, northern Tibet: A linkage between accretionary and collisional orogenesis

Kusky

Wilde

et al. 2018

GSA Bulletin

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Collision-related magmatism in accretionary-to-collisional orogens records a tectonic transition from early subductionaccretionary processes to collisional orogenesis, and also plays a significant role in continental growth. Here, we present an integrated study of field observations, geochemistry, whole-rock Rb-Sr and Sm-Nd isotopes, and zircon U-Pb ages and Lu-Hf isotopes for the Laohushan mafic to felsic magmatic rocks related to initial collision between the Alxa terrane and the Central Qilian block along the North Qilian orogenic belt, northeastern Tibet. The Laohushan magmatic rocks are dominated by quartz diorites (ca. 426 Ma), with minor tonalites enclosing dioritic enclaves (ca. 430 Ma) and hornblendite xenoliths (ca. 448 Ma), and some coeval dolerite dikes (ca. 427 Ma) intruded into the accretionary complex. The quartz diorites are characterized by light rare earth element (LREE)-and large ion lithophile element (LILE)-enrichment but have high field strength element (HFSE)-depleted trace element patterns and negative initial ε Nd (-1.6 to-2.9) and positive zircon initial ε Hf (+3.0 to +6.2) values. The dioritic enclaves are also characterized by LREE-enriched and HFSE-depleted patterns and have mostly negative initial ε Nd (-9.2 to +0.03) but positive zircon initial ε Hf (+3.0 to +5.9) values. These geochemical and isotopic features, together with isotopic mixing calculations, suggest that the quartz diorites were likely derived from partial melting of the lower crust dominated by accreted mafic oceanic rocks with minor sediments, whereas the dioritic enclaves originated from underplated mantlederived magmas mixed with crust-derived melts. The hornblendite xenoliths have high MgO, Cr, and Ni contents, positive Th, U, and Pb anomalies, and negative Nb, Ta, and Ti anomalies. They have negative initial ε Nd (-2.8), near chondritic zircon initial ε Hf (-0.4 to +1.4) values and an Archean Nd model age (T DM = 2.74 Ga), suggesting that the hornblendites were likely produced by partial melting of subcontinental lithospheric mantle peridotite that was metasomatized by subduction-related melts beneath the Archean-Proterozoic Alxa terrane. We propose that partial melting of the lower crust of the early Paleozoic North Qilian orogenic belt was in response to slab breakoff and asthenospheric upwelling during the initial stage of collisional orogenesis. This study demonstrates that heterogeneous magma sources, involving accretionary materials (i.e., accreted oceanic crust and sediments) and various mantle-derived components, were mixed to form the collision-related magmatic rocks. It also highlights the significance of collisionrelated magmatism in continental growth and stabilization of newly-assembled crust in accretionary-to-collisional orogens.

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Section: Introductionmentioning

confidence: 80%

Early Paleozoic collision-related magmatism in the eastern North Qilian orogen, northern Tibet: A linkage between accretionary and collisional orogenesis

Kusky

Wilde

et al. 2018

GSA Bulletin

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“…Studies on the petrogenesis of syn-collisional granitoids are important for testing this hypothesis. Our studies on syn-J o u r n a l o f P e t r o l o g y a c c e p t e d m a n u s c r i p t ( 2 0 2 0 0 3 0 5 ) collisional granitoids with mafic magmatic enclaves (MMEs) from orogens on the Tibetan Plateau and adjacent regions (e.g., Qinling, Kunlun and Qilian orogens) support this hypothesis in many aspects, including significant mantle Nd-Hf isotopic contributions to the granitoids (Huang et al, 2014(Huang et al, , 2015(Huang et al, , 2016(Huang et al, , 2017Chen et al, 2015Chen et al, , 2016Chen et al, , 2018Li et al, 2016Li et al, , 2017Duan et al, 2016;Zhang et al, 2016;Kong et al, 2017). Nevertheless, quantification is necessary in order to develop this testable hypothesis into a comprehensive theory.…”

Section: Introductionmentioning

confidence: 99%

“…Comprehensive geochemical studies on both major and accessory minerals are thus necessary to genuinely understand the petrogenesis of igneous rocks (e.g., Bachmann et al, 2005;Gao et al, 2009). In this paper, we present mineral in situ trace element data on two well-characterized syn-collisional granitoid plutons, i.e., the Baojishan (BJS) and Qumushan (QMS) plutons in the North Qilian Orogen (NQO) on the northern margin of the Tibetan Plateau (Chen et al, 2015(Chen et al, , 2016(Chen et al, , 2018. Both QMS and BJS plutons have similarly abundant MMEs in sharp contact with host granitoids, while the QMS host granitoids show adakitic characteristics, which is different from the QMS MMEs or the J o u r n a l o f P e t r o l o g y a c c e p t e d m a n u s c r i p t ( 2 0 2 0 0 3 0 5 ) interpreted as resulting from fractional crystallization of primitive andesitic magmas (Chen et al, 2016), it needs quantifying by considering detailed and specific controls of different crystallized minerals in the granitoid systems.…”

Section: Introductionmentioning

confidence: 99%

Mineral Compositions of Syn-collisional Granitoids and their Implications for the Formation of Juvenile Continental Crust and Adakitic Magmatism

Xiao

Chen

Niu

et al. 2020

Journal of Petrology

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Continentalcollision zones have been proposed as primary sites of net continental crustal growth. Therefore, studies on syn-collisional granitoids with mafic magmatic enclaves (MMEs) are essential for testing this hypothesis. The Baojishan (BJS) and Qumushan (QMS) syn-collisional plutons in the North Qilian Orogen (NQO) on the northern margin of the Tibetan Plateau have abundant MMEs in sharp contact with host granitoids, sharing similar constituent minerals but with higher modal abundances of mafic minerals in MMEs. The QMS host granitoids have high Sr/Y and La/Yb ratios, showing adakitic compositions, which are differentfrom the BJS granitoids. Based on bulk-rock compositions and zircon U-Pb age-dating, recent studies on these two plutons proposed that MMEs represent cumulates crystallized early from the same magmatic system as their host granitoids, and their parental melts are best understood as andesitic magmas produced by partial melting of the underthrusting upper ocean crust upon collision with some terrigenous sediments under amphibolite facies. Here, we focus on the trace-element geochemistry of the constituent mineral phases of both MMEs and their host granitoids of the QMS and BJS plutons. Weshow that different mineral phases preferentially host different trace elements; for example, most rare earth elements (REEs and Y) reside in titanite (only found in the QMS pluton), amphibole, apatite, epidote and zircon (mostly heavy-REEs); and high-field-strength elements (HFSEs) reside in biotite, titanite, amphibole and zircon. Based on the mineral chemical data, we show that for these two plutons, MMEs are of similar cumulate origin, crystallized from primitive andesitic melts in the early stage of granitoid magmatism. The primitive andesitic melts for these syn-collisional granitoids are most likely produced by the partial melting of the oceanic crust, supporting the hypothesis of continental crustal growth considering the syn-collisional granitoids represent juvenile continental crust. As evidenced by distinct mineral compositions, the two plutons have different parental magma compositions, for example higher TiO2 content and higher Sr/Y and La/Yb ratios in the QMS parental magmas, a signature best understood as being inherited from the source. The higher TiO2 content of the parental magma for the QMS pluton leads to the common presence of titanite in the QMS pluton (absent in the BJS pluton), crystallization of which in turn controls the trace-element (REE, Y, Nb, Ta and others) systematics in the residual melts towards an adakitic signature. Therefore, parental magmas with high TiO2 content and high Sr/Y and La/Yb ratios, as well as their further fractionation of titanite, are important factors in the development of adakitic compositions, as represented by the QMS host granitoids. This model offers a new perspective on the petrogenesis of adakitic rocks. The present study further demonstrates that, in general, mineral chemistry holds essential information for revealing the petrogenesis of granitoid rocks.

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“…The Qilian orogen underwent a complex orogenic process in the Early Paleozoic (e.g., Xiao et al, 2009a;Song et al, 2013;Huang et al, 2014aHuang et al, , 2014bHuang et al, , 2015aHuang et al, , 2015bHuang et al, , 2016Wu et al, 2016Wu et al, , 2017Liu et al, 2018aLiu et al, , 2018bZuza et al, 2018;Chen et al, 2018). In the past two decades, the petrogenesis and tectonic settings of different types of igneous rocks in the Qilian orogen have been widely studied (e.g., Song et al, 2013;Tseng et al, 2009;Wu et al, 2009;Huang et al, 2014aHuang et al, , 2015aTung et al, 2016;Wang et al, 2017;Zuza et al, 2018;Chen et al, 2018). However, several important firstorder problems regarding the development of the Qilian orogeny remain unresolved.…”

Section: Introductionmentioning

confidence: 99%

“…Early Paleozoic intrusive rocks are widespread in this region. We have completed detailed (1:50,000 scale) geological mapping around this area for five years, and it is an ideal place to study the tectonic evolution of the North Qilian Ocean and the relationship between the Qilian and its neighboring terranes during the Early Paleozoic (Feng and He, 1996;Wu et al, 2016Wu et al, , 2017Liu et al, 2018a;Zuza et al, 2018;Chen et al, 2018). In this paper, newly acquired U-Pb zircon ages and geochemical data are presented for intrusive rock samples collected from the study area.…”

Section: Introductionmentioning

confidence: 99%

Petrogenesis and tectonic significance of Early Paleozoic magmatism in the northern margin of the Qilian block, northeastern Tibetan Plateau

Liu

Song

et al. 2019

Lithosphere

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Abundant Early Paleozoic magmatism is preserved in northern Tibet and has important implications for continental crustal growth in response to continental collisions. To better constrain the evolution of the northern margin of the Tibetan Plateau and the resulting closure of the North Qilian Ocean, we conducted an integrated investigation involving U-Th-Pb zircon geochronology, whole-rock geochemistry, and syntheses of existing data sets across the North Qilian orogenic belt. Zircon U-Pb dating indicates that the Early Paleozoic intrusive rocks in the study area can be divided into two stages: 460-480 Ma and 440 Ma. The 478-480 Ma meta gabbro-diorite samples belong to the calc-alkaline series and show a fractional crystallization trend in the Harker diagrams. These samples have relatively high La/Nb (2.08-3.26) and low La/Ba (0.05-0.06) ratios, indicating a subduction-modified continental-lithospheric mantle source. The 460-480 Ma meta-granite samples are I-type and classified as high-K calc-alkaline series. Both the meta gabbro-diorite and meta-granite samples are characterized by negative Nb, Ta, and Ti anomalies and enriched LILEs, and showing arc signatures that may be related to the southward subduction of the North Qilian oceanic crust. The 441 Ma hornblende syenite samples have high contents of alkalis (K 2 O +Na 2 O = 7.80%-12.07%) and belong to the alkaline series, suggesting an extensional geological setting. The 440 Ma syenogranite samples are classified as high Ba-Sr granites and belong to the shoshonitic series. The syenogranite samples were most likely generated by partial melting of lithospheric mantle that had been metasomatized by slab-derived fluids, and mixed by the crust derived granitic magmas during the ascent of the magma. Both the hornblende syenite (441 Ma) and the syenogranite (440 Ma) samples were emplaced in a postcollisional tectonic setting associated with the closure process of the North Qilian Ocean.

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Syn-collisional felsic magmatism and continental crust growth: A case study from the North Qilian Orogenic Belt at the northern margin of the Tibetan Plateau

Cited by 24 publications

References 77 publications

Early Paleozoic collision-related magmatism in the eastern North Qilian orogen, northern Tibet: A linkage between accretionary and collisional orogenesis

Early Paleozoic collision-related magmatism in the eastern North Qilian orogen, northern Tibet: A linkage between accretionary and collisional orogenesis

Mineral Compositions of Syn-collisional Granitoids and their Implications for the Formation of Juvenile Continental Crust and Adakitic Magmatism

Petrogenesis and tectonic significance of Early Paleozoic magmatism in the northern margin of the Qilian block, northeastern Tibetan Plateau

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