Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

F. Hervé; F. Greene; R. J. Pankhurst

doi:10.1016/0895-9811(94)90012-4

Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

F. Hervé, F. Greene, R. J. Pankhurst

Engineering School

Research output: Contribution to journal › Article › peer-review

11 Citations (Scopus)

Abstract

A 15 km² body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic mélange as determined by illite crystallinity studies. Isotopic modification of the RbSr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S₂ foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.

Original language	English
Pages (from-to)	263-270
Number of pages	8
Journal	Journal of South American Earth Sciences
Volume	7
Issue number	3-4
DOIs	https://doi.org/10.1016/0895-9811(94)90012-4
Publication status	Published - 1994

ASJC Scopus subject areas

Geology
Earth-Surface Processes

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10.1016/0895-9811(94)90012-4

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@article{6d2e0028264444859bdacd7f9b4b4638,

title = "Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile",

abstract = "A 15 km2 body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic m{\'e}lange as determined by illite crystallinity studies. Isotopic modification of the RbSr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S2 foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.",

author = "F. Herv{\'e} and F. Greene and Pankhurst, {R. J.}",

note = "Funding Information: AcknowledgmentswThe field work was supported by FONDECYT Grants 0914 and 1181 to FH. A JICA (Japan International Cooperation Agency) scholarship to FG allowed the microprobe analysis at the Geological Survey of Japan. E. Godoy, L. L6pez, E. Nelson, and R. Forsythe made useful suggestions that improved the text. Prof. Hubert Miller made the arrangements for the whole rock geochemical analyses to be carried out at the University of Miinchen. E Eggers and D. Morata assisted with the computer chemistry plots. Rb-Sr isotopic data were obtained at the NERC Isotope Geosciences Laboratory (NIGL), Nottingham, UK, with the approval of Dr. R. Harmon, and this paper is recorded as NIGL Publication N ° 66. FH also acknowledges help received at the Laboratoire de Petrologie, Universit6 d'Aix Marseille III during an European Community scholarship. This paper is a contribution to the International Geological Correlation Program Project N'279 ({"}Terranes of Latin America{"}).",

year = "1994",

doi = "10.1016/0895-9811(94)90012-4",

language = "English",

volume = "7",

pages = "263--270",

journal = "Journal of South American Earth Sciences",

issn = "0895-9811",

publisher = "Elsevier BV",

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T1 - Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

AU - Hervé, F.

AU - Greene, F.

AU - Pankhurst, R. J.

N1 - Funding Information: AcknowledgmentswThe field work was supported by FONDECYT Grants 0914 and 1181 to FH. A JICA (Japan International Cooperation Agency) scholarship to FG allowed the microprobe analysis at the Geological Survey of Japan. E. Godoy, L. L6pez, E. Nelson, and R. Forsythe made useful suggestions that improved the text. Prof. Hubert Miller made the arrangements for the whole rock geochemical analyses to be carried out at the University of Miinchen. E Eggers and D. Morata assisted with the computer chemistry plots. Rb-Sr isotopic data were obtained at the NERC Isotope Geosciences Laboratory (NIGL), Nottingham, UK, with the approval of Dr. R. Harmon, and this paper is recorded as NIGL Publication N ° 66. FH also acknowledges help received at the Laboratoire de Petrologie, Universit6 d'Aix Marseille III during an European Community scholarship. This paper is a contribution to the International Geological Correlation Program Project N'279 ("Terranes of Latin America").

PY - 1994

Y1 - 1994

N2 - A 15 km2 body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic mélange as determined by illite crystallinity studies. Isotopic modification of the RbSr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S2 foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.

AB - A 15 km2 body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic mélange as determined by illite crystallinity studies. Isotopic modification of the RbSr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S2 foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.

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U2 - 10.1016/0895-9811(94)90012-4

DO - 10.1016/0895-9811(94)90012-4

M3 - Article

AN - SCOPUS:0028579166

SN - 0895-9811

VL - 7

SP - 263

EP - 270

JO - Journal of South American Earth Sciences

JF - Journal of South American Earth Sciences

IS - 3-4

ER -

Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

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