Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

scholarly journals Geochronology and Sr–Nd–Hf isotope constraints on the petrogenesis of teschenites from the type-locality in the Outer Western Carpathians

2019 ◽  
Vol 70 (3) ◽  
pp. 222-240 ◽  
Author(s):  
Irena Brunarska ◽  
Robert Anczkiewicz
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Mantle Metasomatism ◽  
Alkaline Magmatism ◽  
Asthenospheric Mantle ◽  
Depleted Mantle ◽  
Outer Western Carpathians ◽  
Wide Range ◽  
Mantle Component

Abstract The Teschenite Association Rocks (TAR) in the Outer Western Carpathian (OWC) flysch form a classic suite of alkaline intrusions where teschenite and picrite were first defined. They represent continental intraplate volcanism that produced a wide range of melano- to mesocratic rocks emplaced during the Early Cretaceous rifting within the southern margin of the European Plate. Geochemical modelling indicates that they may be a product of ~2–5 % partial melting of the metasomatised, asthenospheric mantle. The variations in REE (low / heavy REE content, LaN/YbN = 11–34) are consistent with deep melting of garnet peridotite. Initial ε(Nd)i = 5.0–6.3 and ε(Hf)i = 4.9–10.0 preclude the significant mature crust involvement. Instead, a linear array formed by the 143Nd/144Nd and 176Hf/177Hf isotopic ratios points to a genesis from the mixed, HIMU–OIB source with the more depleted, MORB-type component. Mantle metasomatism was most likely caused by the Variscan subduction–collision processes as indicated by the depleted mantle Nd model ages. The isotope and trace element ratios of the TAR resemble the European Asthenospheric Reservoir (EAR) — the common mantle end-member for the widespread Cenozoic volcanic rocks in Europe. This confirms a long-term existence of the EAR mantle component beneath the Central Europe, at least since the Early Cretaceous. In situ laser-ablation ICP-MS U–Pb dating of titanite indicates short duration of mafic alkaline magmatism in the OWC, lasting from 123.7 ± 2.1 to 117.9 ± 1.8 Ma. Emplacement of the TAR is correlated with the maximum lithospheric thinning that triggered adiabatic decompression and partial melting of the upwelling asthenospheric mantle. Magmatism ceased most likely due to transition to the dominantly compressive regime associated with the major stress field reorganization directly preceding the Carpathian– Alpine Orogeny.

Geochemistry and petrogenesis of the Early Cretaceous high-K calc-alkaline volcanic rocks in the northern part of Yishu fault, East China

2020 ◽  
Vol 36 (11) ◽  
pp. 3265-3286
Author(s):  
MENG FanChao ◽  
◽  
QU ZhiJing ◽  
CUI Yan ◽  
CHEN Yong ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
East China ◽  
Calc Alkaline ◽  
High K

The eruptive history, magmatic evolution, and influence of glacial ice at long-lived Akutan volcano, eastern Aleutian Islands, Alaska, USA

2020 ◽  
Author(s):  
Michelle L. Coombs ◽  
Brian R. Jicha
Keyword(s):  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Geochemical Data ◽  
Mantle Melting ◽  
Aleutian Island ◽  
Evolutionary Trend ◽  
Eruptive Activity ◽  
Calc Alkaline ◽  
Wide Range ◽  
Magma System

New 40Ar/39Ar and whole-rock geochemical data are used to develop a detailed eruptive chronology for Akutan volcano, Akutan Island, Alaska, USA, in the eastern Aleutian island arc. Akutan Island (166°W, 54.1°N) is the site of long-lived volcanism and the entire island comprises volcanic rocks as old as 3.3 Ma. Our current study is on the 225 km2 western half of the island, where our results show that the focus of volcanism has shifted over the last ∼700 k.y., and that on occasion, multiple volcanic centers have been active over the same period, including within the Holocene. Incremental heating experiments resulted in 56 40Ar/39Ar plateau ages and span 2.3 Ma to 9.2 ka. Eruptive products of all units are primarily tholeiitic and medium-K, and range from basalt to dacite. Rare calc-alkaline lavas show evidence suggesting their formation via mixing of mafic and evolved magmas, not via crystallization-derived differentiation through the calc-alkaline trend. Earliest lavas are broadly dispersed and are almost exclusively mafic with high and variable La/Yb ratios that are likely the result of low degrees of partial mantle melting. Holocene lavas all fall along a single tholeiitic, basalt-to-dacite evolutionary trend and have among the lowest La/Yb ratios, which favors higher degrees of mantle melting and is consistent with the increased magma flux during this time. A suite of xenoliths, spanning a wide range of compositions, are found in the deposits of the 1.6 ka caldera-forming eruption. They are interpreted to represent completely crystallized liquids or the crystal residuum from tholeiitic fractional crystallization of the active Akutan magma system. The new geochronologic and geochemical data are used along with existing geodetic and seismic interpretations from the island to develop a conceptual model of the active Akutan magma system. Collectively, these data are consistent with hot, dry magmas that are likely stored at 5−10 km depth prior to eruption. The prolonged eruptive activity at Akutan has also allowed us to evaluate patterns in lava-ice interactions through time as our new data and observations suggest that the influence of glaciation on eruptive activity, and possible magma composition, is more pronounced at Akutan than has been observed for other well-studied Aleutian volcanoes to the west.

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