Yan, Quanshu; Zhang, Pingyang; Metcalfe, Ian; Liu, Yanguang; Wu, Shiying; Shi, Xuefa

Author(s)

Yan, Quanshu

Zhang, Pingyang

Metcalfe, Ian

Liu, Yanguang

Wu, Shiying

Shi, Xuefa

Publication Date

2019

Abstract

The Mariana Trough, a relatively simple intra-oceanic back-arc basin, is ideal for investigating magmatic processes and mantle- crust interaction in a subduction setting. We present new major- and trace element compositions for 31 basaltic lava and glass samples from the Mariana Trough back-arc spreading center. The studied lavas include phenocrysts of plagioclase, olivine and pyroxene. Major element compositions show that these lavas range from tholeiitic basalt to basaltic andesite, and belong to a sub- alkali tholeiitic series produced by fluid-influenced fractional crystallization of primary basaltic melts. Trace element composi- tions show that these lavas are transitional between typical normal mid-ocean ridge basalts (MORB) and island arc basalt (IAB), and are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs). Trace element ratios, e.g., Ba/Th, Pb/Ce, Th/Nd, La/Sm, Th/Nb, Ba/Nb and Th/Nb, indicate that the mantle from which these lavas were derived underwent modification resulting from the addition of multiple subduction components. Some typical trace element ratios (e.g., Ba/Nb- total subduction component, Ba/Th- shallow subduction, and Th/Nb-deep subduction component) from our new data and the literature suggest that a latitudinal variation exists in addition to subduction components, and indicates a more complex and heterogeneous distribution of subduction components in the Mariana back-arc region. We suggest that, (1) compared to back-arc locations at 18° N and 15.5° N, lavas from back-arc locations at 17° N indicate higher levels of modification by hydrous fluid released from the subducted slab, and (2) compared to back-arc locations at 17° N and 15.5° N, petrogenesis of lavas from back-arc locations at 18° N indicates a greater influence of sediment melt.

Citation

Mineralogy and Petrology, 113(6), p. 803-820

ISSN

1438-1168

0930-0708

Link

https://hdl.handle.net/1959.11/28736

Publisher

Springer Wien

Title

Geochemistry of axial lavas from the mid-and southern Mariana Trough, and implications for back-arc magmatic processes

Type of document

Journal Article

Entity Type

Publication

Author(s)	Yan, Quanshu Zhang, Pingyang Metcalfe, Ian Liu, Yanguang Wu, Shiying Shi, Xuefa
Publication Date	2019
Abstract	The Mariana Trough, a relatively simple intra-oceanic back-arc basin, is ideal for investigating magmatic processes and mantle- crust interaction in a subduction setting. We present new major- and trace element compositions for 31 basaltic lava and glass samples from the Mariana Trough back-arc spreading center. The studied lavas include phenocrysts of plagioclase, olivine and pyroxene. Major element compositions show that these lavas range from tholeiitic basalt to basaltic andesite, and belong to a sub- alkali tholeiitic series produced by fluid-influenced fractional crystallization of primary basaltic melts. Trace element composi- tions show that these lavas are transitional between typical normal mid-ocean ridge basalts (MORB) and island arc basalt (IAB), and are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs). Trace element ratios, e.g., Ba/Th, Pb/Ce, Th/Nd, La/Sm, Th/Nb, Ba/Nb and Th/Nb, indicate that the mantle from which these lavas were derived underwent modification resulting from the addition of multiple subduction components. Some typical trace element ratios (e.g., Ba/Nb- total subduction component, Ba/Th- shallow subduction, and Th/Nb-deep subduction component) from our new data and the literature suggest that a latitudinal variation exists in addition to subduction components, and indicates a more complex and heterogeneous distribution of subduction components in the Mariana back-arc region. We suggest that, (1) compared to back-arc locations at 18° N and 15.5° N, lavas from back-arc locations at 17° N indicate higher levels of modification by hydrous fluid released from the subducted slab, and (2) compared to back-arc locations at 17° N and 15.5° N, petrogenesis of lavas from back-arc locations at 18° N indicates a greater influence of sediment melt.
Citation	Mineralogy and Petrology, 113(6), p. 803-820
ISSN	1438-1168 0930-0708
Link	https://hdl.handle.net/1959.11/28736
Publisher	Springer Wien
Title	Geochemistry of axial lavas from the mid-and southern Mariana Trough, and implications for back-arc magmatic processes
Type of document	Journal Article
Entity Type	Publication

Geochemistry of axial lavas from the mid-and southern Mariana Trough, and implications for back-arc magmatic processes

Files: