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First Discovery of a Nonophiolite-Type Spinel Lherzolite Xenolith in the Back-Arc Basin of the Mariana Island Arc System
Oceanology ( IF 1 ) Pub Date : 2020-10-09 , DOI: 10.1134/s0001437020040128
A. V. Koloskov , V. A. Rashidov , V. V. Ananyev

Abstract

The first sampling of mantle horizons underlying the ophiolite peridotite complex of the Mariana back-arc basin was carried out based on a spinel lherzolite xenolith in basanites from the submarine Esmeralda Volcano. The paper shows significant differences between the bulk, petrological, geochemical, and mineralogical compositions of this xenolith and similar characteristics of ophiolite peridotites dredged from the Central Trough of the north part of the Mariana Trench, on the west wall of one of the fault zones of the Santa Rosa Bank Fault (southern part of the trough), and ultramafic rocks dredged from the Conical and Torishima seamounts in the fore-arc part of the Mariana and Idzu-Bonin Island Arc Systems. Using different geothermometers and geobarometers, we revealed the PT conditions for the formation of Esmeralda xenolith’s mineral paragenesis. The optimal temperature is 950–1050°C and the pressure is 13–15 kbar. These parameters significantly exceed those suggested for the compared ophiolite peridotites.



中文翻译:

在马里亚纳岛弧系统的后弧盆地中首次发现了非蛇绿岩型尖晶石斜纹沸石异岩。

摘要

马里亚纳后弧盆地蛇绿岩橄榄岩复合体下面的地幔层位的首次采样是基于海底埃斯梅拉达火山中的玄武岩中的尖晶石锂铁矿异岩。本文显示了该异岩的体积,岩石学,地球化学和矿物学组成之间的显着差异,以及从马里亚纳海沟北部北部中部海槽挖出的蛇绿橄榄岩橄榄岩的相似特征,该断层之一位于西伯利亚断层带的西壁上。圣罗莎银行断层(海槽的南部),以及从马里亚纳群岛和伊祖-波宁岛弧系前弧部分的圆锥形和鸟岛海山挖出的超镁铁质岩石。使用不同的地热仪和地压仪,我们揭示了Esmeralda xenolith矿物共生形成的PT条件。最佳温度为950–1050°C,压力为13–15 kbar。这些参数大大超过建议的蛇绿岩橄榄岩建议的参数。

更新日期:2020-10-11
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