Influence of slab thermal structure on basalt source regions and melting conditions: REE and HFSE constraints from the Garibaldi volcanic belt, northern Cascadia subduction system

Green, Nathan L.

doi:10.1016/j.lithos.2005.05.003

Cited by 153 publications

(52 citation statements)

References 45 publications

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“…Based on this long-held assumption, HFSE have often been used as indices that can see through the slab signature and investigate the Zheng et al, 1998;Yeo et al, 2004;Lee et al, 2005;Machado et al, 2005a). Shaded regions indicate the range of incompatible element ratios in average MORB and OIB (Green, 2006). geochemical nature of pre-subduction mantle wedge.…”

Section: Mantle Sourcementioning

confidence: 99%

Trace element and isotopic evidence for temporal changes of the mantle sources in the South Shetland Islands, Antarctica

Lee

Choe

et al. 2008

Geochem. J.

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We present Sr-Nd-Pb isotope data from the Paleocene-Eocene volcanic rocks in King George Island, South Shetland Islands, West Antarctica. We interpret these data in combination with previously published trace and isotope data for Meso-Cenozoic volcanic rocks in the South Shetland Islands to gain a better understanding of the geochemical evolution of the mantle source region. The studied rocks are from four volcanic islands and range in age from 143 to 44 Ma. They have high abundances of large ion lithophile elements and light rare earth elements relative to high field strength elements, consistent with products of subduction related magmatism. The systematic inter-island variations are recognized from a comprehensive examination of the trace elements and isotopic compositions. The degree of enrichment of Sr-Nd-Pb isotopic compositions decreases towards younger samples, while the ratios of fluid-mobile elements/ HFSE (Sr/Yb, Pb/Yb and U/Yb) gradually increase. The previous studies on these volcanic rocks concluded that the compositional variations of the South Shetland Islands volcanic suites were mainly controlled by two component mixing between altered MORB and Pacific sediments. However, we here propose that the compositional trends observed in the volcanic rocks of the South Shetland Islands can be created from the addition of a relatively constant subduction component to temporally varying heterogeneous mantle sources. The higher radiogenic Pb and Sr isotopes and lower 143 Nd/ 144 Nd ratios of the older volcanic rocks from Greenwich and Livingston islands compared to younger rocks can be explained by the significant influence of enriched previously metasomatized mantle material rather than fluids or sediment melts from the subducting slab. In contrast, the geochemical nature of the youngest King George Island volcanic rocks suggests a relatively large contribution of a slab-derived fluid component to the magma generation, but a minor role of the enriched component.

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Section: Mantle Sourcementioning

confidence: 99%

Trace element and isotopic evidence for temporal changes of the mantle sources in the South Shetland Islands, Antarctica

Lee

Choe

et al. 2008

Geochem. J.

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“…Group-I dykes shows LREE fractionated character with respect to chondrite (Sun and McDonough, 1989) and high values of some incompatible element ratios such as Th/Nb, Zr/Y, Ta/Yb and Pb/Yb (Table 3) indicating their generation from a metasomatized mantle source. Group-II dykes with nearly flat REE pattern and relatively low values of incompatible element ratios such as Th/Nb, Zr/Y,Ta/Yb and Pb/Yb (Table 3) likely to have been derived from an (Green, 2006). unmodified mantle source similar to E-MORB.…”

Section: Resultsmentioning

confidence: 99%

Newer Dolerite dykes, Jharkhand, India: a case study of magma generation, differentiation and metasomatism in a subduction zone setting

Sengupta

Ray

2012

Geochem. J.

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belong to different generations (Saha et al., 1973). The geochemical characters of these dykes are strikingly uniform over a long period of time (Bose, 2008;Mallick and Sarkar, 1994). Bose (2008) suggested that Newer Dolerite dykes generated through partial melting of subcontinental mantle which in turn was metasomatised. Mir et al. (2010) documented geochemical characteristics of these dykes similar to those of back arc extension basalts (BABB). In the studied area shear fractures which appears to act as pathways of these mafic intrusives have two dominant trends NE-SW and E-W and a subsidiary NW-SE trends. This might suggest that stress system have not an uniform direction over a long period, but it changed orientation with time. The geochemical classification of these dykes and their linking to possible tectonic settings have not yet been reported by earlier workers. In the present work, attempts have been made to classify these dykes according to their trace and REE composition. The genesis of different chemical types of Newer Dolerite dykes has been discussed in the perspective of possible tectonic setting. GEOLOGICAL SETTINGThere is a prevalent idea to consider the Singhbhum craton as a "greenstone granite terrain" (Mahadevan, The NE-SW, NW-SE and E-W trending Proterozoic Newer Dolerite dykes around Chaibasa, Jharkhand, India are found to intrude Singhbhum Granites of late Archean age. Clouded plagioclase, bastitised orthopyroxene and uralitized clinopyroxene, magnetite-ilmenite, quartz-feldspar granophyric intergrowth are the characteristic minerals present in the dolerite dykes which assign a low grade metamorphosed character to the dolerite. Both olivine normative and quartz normative varieties are observed in this suite of dykes. These dolerites have been classified into two groups on the basis of REE distribution patterns: one with LREE (Light Rare Earth Element) enriched pattern (Group I) and the other with flat REE pattern (Group II). A significant positive correlation among trace elements Nb, Zr, La, Ce for Group I dykes suggest variable degree of partial melting of the mantle source. In tectonic discrimination diagrams made with immobile incompatible trace elements Nb, Zr, Ti and Y, Group I dykes show arc-like geochemical signature while Group II dykes are similar to MORBs. Enrichment in some of the LILE and prominent depletion in Nb, P and Ti in Group I dykes suggest that the original melt was derived from a metasomatised mantle source. Group II dykes might derived from a MORB-type mantle source. Melting was triggered by volatiles in case of dykes of Group I while for the Group II dykes, melting was produced by thinning of the lithosphere and subsequent decompression.

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“…7B). The partial melting trajectories that coincide with the quartz diorite and the basaltic andesite compositions imply >5% partial melting of an enriched mantle source based upon La abundance and La/Sm ratios (e.g., Green, 2006;Zhu et al, 2009) (Fig. 8A).…”

Section: The Calc-alkaline Quartz Diorite and Basaltic Andesitementioning

confidence: 88%

Late Paleozoic calc-alkaline to shoshonitic magmatism and its geodynamic implications, Yuximolegai area, western Tianshan, Xinjiang

et al. 2012

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Influence of slab thermal structure on basalt source regions and melting conditions: REE and HFSE constraints from the Garibaldi volcanic belt, northern Cascadia subduction system

Cited by 153 publications

References 45 publications

Trace element and isotopic evidence for temporal changes of the mantle sources in the South Shetland Islands, Antarctica

Trace element and isotopic evidence for temporal changes of the mantle sources in the South Shetland Islands, Antarctica

Newer Dolerite dykes, Jharkhand, India: a case study of magma generation, differentiation and metasomatism in a subduction zone setting

Late Paleozoic calc-alkaline to shoshonitic magmatism and its geodynamic implications, Yuximolegai area, western Tianshan, Xinjiang

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