کد مقاله کد نشریه سال انتشار مقاله انگلیسی ترجمه فارسی نسخه تمام متن
4716124 1638683 2014 27 صفحه PDF سفارش دهید دانلود رایگان
عنوان انگلیسی مقاله ISI
Episodic magmatism at 105 Ma in the Kinki district, SW Japan: Petrogenesis of Nb-rich lamprophyres and adakites, and geodynamic implications
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موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Episodic magmatism at 105 Ma in the Kinki district, SW Japan: Petrogenesis of Nb-rich lamprophyres and adakites, and geodynamic implications
چکیده انگلیسی


• The ca. 105 Ma episodic magmatism and its geodynamic implications are described.
• A model of Early Cretaceous slab rollback beneath the forearc is proposed.
• The accompanying asthenosphere upwelling formed a transitory thermal anomaly.
• The thermal anomaly induced a melting of oceanic crust to form adakitic granitoids.
• Melting of metasomatized mantle wedge produced lamprophyre.

Cretaceous episodic magmatism produced Nb-rich lamprophyres and adakitic granitoids in the Kinki district of SW Japan. K–Ar dating of minerals from the lamprophyres, adakites, and hornblende peridotite xenoliths yielded ages of 109–99 Ma, indicating a short-lived episodic magmatism. The lamprophyres generally display primitive high-Mg basaltic to basaltic andesite compositions with high Mg# and high Cr and Ni contents that preclude substantial differentiation. Some high-Nb basalt (HNB) and Nb-enriched basalt (NEB) compositions also occur. The lamprophyres have high large-ion lithophile element (LILE) and high field-strength element (HFSE) contents and variable (La/Yb)n ratios, and can be divided into high-(La/Yb)n (12.5–22.1) and low-(La/Yb)n (3.6–6.1) groups. The former contains nepheline-normative rocks with positive initial εNd(T) values, whereas the latter contains hypersthene-normative subalkaline rocks with negative initial εNd(T) values. The adakitic granitoids have relatively high TiO2, Nb, and Ta contents compared to more typical high-silica adakites elsewhere, indicating that they were produced by high temperatures (ca. 920 to 970 °C) during slab melting.Early Cretaceous slab rollback and the accompanying asthenospheric upwelling at 105 Ma could form a transitory thermal anomaly, and hence induce melting of the subducted slab to form adakitic granitoids, and produce metasomatized wedge mantle to form the lamprophyres. The high-(La/Yb)n lamprophyres originated from small degrees of partial melting of an enriched metasomatized mantle wedge within the garnet stability field at depths of ≥ 70 km, whereas the low-(La/Yb)n lamprophyres originated from a different mantle source by a comparatively larger degree of partial melting in a relatively shallow part of the mantle wedge. The magmatic diversity of the Kyoto lamprophyres thus derives primarily from a heterogeneous mantle source that has been variably affected by the results of subduction.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 184–187, January 2014, Pages 105–131
نویسندگان
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