The identification and significance of pure sediment-derived granites

Hopkinson, Thomas; Harris, Nigel; Warren, Clare J.; Spencer, Christopher J.; Roberts, Nick M.W.; Horstwood, Matthew; Parrish, Randall R.; Eimf,

doi:10.1016/j.epsl.2017.03.018

Cited by 175 publications

(58 citation statements)

References 46 publications

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“…4C, 4D), the ECS rocks straddle the fields of syncollisional granitoids and that of volcanic arc granites, a feature characteristic of many granitoids that are neither true volcanic arc nor Himalayan type (cf. Hopkinson et al, 2017). The same pattern is displayed by the granitoids of the POS of northwest Iberia on these diagrams (cf.…”

Section: General Geochemical Features and Classification Of The Ecs Gsupporting

confidence: 52%

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

et al. 2018

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In this study we report laser ablation-inductively coupled plasma-mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347-337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.

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Section: General Geochemical Features and Classification Of The Ecs Gsupporting

confidence: 52%

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

et al. 2018

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“…Mixing model results show that the enriched mantle source of the Konglong enclaves can be a hybrid mantle consisting of the DMM and 1–2% melts derived from the Indian continental crust. Notably, the Konglong enclaves have high zircon δ 18 O values of 8.1–8.9‰ within the range of those of the Greater Himalayan Sequence and its leucogranites (6.9–12.5‰; Hopkinson et al, ), further arguing for a mantle source metasomatized by the Indian continental crust.…”

Section: Discussionmentioning

confidence: 96%

First Identification of Mafic Igneous Enclaves in Miocene Lavas of Southern Tibet With Implications for Indian Continental Subduction

Hao

Wang

Wyman

et al. 2018

Geophysical Research Letters

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The history of Indian continental subduction beneath Asian plate remains unclear. Miocene ultrapotassic rocks in southern Tibet, with extremely enriched isotopes, have often been used to trace mantle metasomatism and geodynamic processes associated with Indian continental subduction. These rocks, however, may have been contaminated by Lhasa ancient crust. Uncertainties on primary ultrapotassic magmas obscure their mantle sources. Here we report on first mafic igneous enclaves in Cenozoic lavas of southern Tibet. They consist principally of clinopyroxene, phlogopite, and sanidine and have a zircon U‐Pb age of 21.5 ± 0.3 Ma. Mineral and bulk‐rock geochemical characteristics indicate their crystallization from primary ultrapotassic magmas. Bulk‐rock Sr‐Nd, clinopyroxene Sr, and zircon O isotopes demonstrate their isotopically enriched character. Combined with precollisional basalts, we suggest that the mantle source of the enclaves was enriched by the subducted Indian continent. This study implies that the Indian continent had subducted beneath central Lhasa no later than early Miocene.

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“…However, the Th/La ratios of sediment‐derived melts are almost constant (0.3–0.4; e.g., Castro et al, ) and significantly lower than those of the Group II samples (Th/La = 0.5–1.0, Figure a). This difference, together with the low zircon δ 18 O values (5.0–7.1‰) of the Group II samples compared to the δ 18 O values of typical continental sediments as exemplified by the Great Himalayan Series (δ 18 O = 8 to 14‰) (Hopkinson et al, ; Massey, Harmon, et al, ; Massey, Reddy, et al, ), indicate that the Group II samples are unlikely derived from the partial melting of K‐rich sediments.…”

Section: Discussionmentioning

confidence: 97%

Transition From Low‐K to High‐K Calc‐Alkaline Magmatism at Approximately 84 Ma in the Eastern Pontides (NE Turkey): Magmatic Response to Slab Rollback of the Black Sea

et al. 2018

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Compositional changes of magma in space and time can be used to infer mantle dynamics and crust‐mantle interaction that are responsible for the generation of magma and evolution. This study reveals, for the first time, the presence of magma compositional transition at approximately 84 Ma in the eastern Pontides arc (NE Turkey), providing important insights into the mantle dynamics responsible for the generation of the extensive Late Cretaceous arc magmatism. The Late Cretaceous granitoids can be divided geochemically into two groups. Group I samples were emplaced at 91–86 Ma and are characterized by low K2O/Na2O, whereas Group II samples were emplaced at 83–78 Ma and display high K2O/Na2O. Group I samples have positive zircon εHf (t), whole‐rock ɛNd (t), and mantle‐like zircon δ18O, which significantly differs from the Group II samples with negative to positive εHf (t), negative whole‐rock ɛNd (t), and enhanced zircon δ18O. The Nd‐Hf‐O isotopic compositions of the Group I and II samples can be quantitatively interpreted as being derived from partial melting of the low‐K amphibolite source within the juvenile lower arc crust that incorporated 5–30% and 50–60% enriched components from the basement rocks into the magmatic systems, respectively. Considering the occurrences of regional thermal subsidence and extensional structure during the Late Cretaceous, the compositional transition from Group I to II and the coeval magmatic flare‐up represented by Group II samples can be linked with the slab rollback of the southward subducting Black Sea (Paleotethys) oceanic lithosphere.

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The identification and significance of pure sediment-derived granites

Cited by 175 publications

References 46 publications

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

First Identification of Mafic Igneous Enclaves in Miocene Lavas of Southern Tibet With Implications for Indian Continental Subduction

Transition From Low‐K to High‐K Calc‐Alkaline Magmatism at Approximately 84 Ma in the Eastern Pontides (NE Turkey): Magmatic Response to Slab Rollback of the Black Sea

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