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GEOREF RECORD

New perspectives on the origin of olivine-rich troctolites and associated harrisites from the Ligurian ophiolites (Italy)

Maria Rosaria Renna, Riccardo Tribuzio and Luisa Ottolini
New perspectives on the origin of olivine-rich troctolites and associated harrisites from the Ligurian ophiolites (Italy)
Journal of the Geological Society of London (July 2016) 173 (6): 916-932

Abstract

The mid-ocean ridge (MOR)-type gabbroic sequences from the Internal Ligurian ophiolites include olivine-rich troctolite lenses up to tens of metres thick. For one of these lenses, a portion of metre-scale thickness characterized by skeletal to dendritic olivines (harrisites) was observed near the contact with host gabbros. Spinels from the olivine-rich troctolites locally include Ti-pargasite to kaersutite frequently associated with phlogopite to Na-phlogopite. Spinel-hosted amphibole displays rare earth element (REE) patterns characterized by a negative Eu anomaly, thereby recording a magmatic process associated with plagioclase segregation. The amphiboles show variable depletion of light REE (LREE) relative to middle REE (MREE), and heavy REE (HREE) that are weakly enriched to depleted with respect to MREE. Crystallization of the inclusion-bearing spinels is attributed to cooling of hybrid melts that originated by interaction between primitive melts and gabbro-related melts relatively rich in SiO (sub 2) and incompatible elements. Clinopyroxene and amphibole from the harrisites show extensive variability for trace element compositions, albeit characterized by subparallel incompatible element patterns. This chemical variability was most probably acquired in response to rapid crystal growth related to undercooling of the harrisite parental melt. We propose that the melt undercooling was related to interaction of a primitive melt batch with a gabbroic crystal mush. Supplementary material: Details of the analytical technique are available at http://doi.org/10.6084/m9.figshare.c.3284312


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 173
Serial Issue: 6
Title: New perspectives on the origin of olivine-rich troctolites and associated harrisites from the Ligurian ophiolites (Italy)
Affiliation: Universita di Messina, Dipartimento di Scienze, Matematiche e Informatiche Scienze Fisiche e Scienze della Terra, Messina, Italy
Pages: 916-932
Published: 20160722
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 77
Accession Number: 2016-087155
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
N44°15'00" - N44°15'00", E09°34'00" - E09°34'00"
N44°12'00" - N44°12'00", E09°46'60" - E09°46'60"
Secondary Affiliation: Universita di Pavia, ITA, Italy
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201643
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