气候变化领域集成服务门户(CCPortal): Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR)

CCPortal

DOI	10.1016/j.tecto.2021.229001
	Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR)
	Ferrando C.; Basch V.; Ildefonse B.; Deans J.; Sanfilippo A.; Barou F.; France L.
发表日期	2021
ISSN	00401951
卷号	815
英文摘要	The exposure of gabbroic sequences at Oceanic Core Complexes (OCC) along ultraslow- to slow-spreading ridges permits the study of the processes forming the lower oceanic crust. On top of the Atlantis Bank OCC along the ultraslow-spreading Southwest Indian Ridge, IODP Expedition 360 drilled Hole U1473A, mainly composed of primitive olivine gabbros interspersed with more evolved Ti-Fe oxide-bearing gabbros and minor felsic veins. These rocks record a complex history of protracted magmatism during continuous uplift and deformation of the gabbroic sequence. Extensive crystal-plastic deformation is dominantly recorded in the shallower sections of the drillhole, whereas the deeper sections better preserve primary magmatic features. We focus on microstructures, including intra-crystalline deformation of rock-forming minerals, and plagioclase crystallographic preferred orientations of olivine gabbros lacking evidence for exhumation-related crystal plastic deformation, to gain insights on the relationship between compaction, melt migration and melt accumulation during the early magmatic history of this section of lower oceanic crust. Olivine gabbros are characterized by ubiquitous grain-size variations, from coarse- to fine-grained intervals. Minerals in coarse-grained intervals show intra-crystalline deformation, while fine-grained crystals lack internal strain. Bent coarse-grained plagioclase associated with weak magmatic foliation and lack of lineation suggest that the coarse-grained intervals were deformed under weak compaction. On the other hand, crystallographic preferred orientations of undeformed fine-grained plagioclase show weak lineations, likely indicative of non-coaxial strain. We thereby infer that the coarse-grained intervals underwent ongoing weak compaction from the stage of olivine + plagioclase ± clinopyroxene crystal mush to the melt-poor stage, and that this process likely aided melt extraction and accumulation in discrete melt-rich zones where crystals orientated in the direction of magmatic flow. Crystallization of melts in the melt-rich zones ultimately formed the fine-grained intervals at different depths in Hole U1473A. This indicates that processes of compaction can lead to local chemical and grain-size heterogeneities in a lower crustal section, while had a minor role in the melt movement at larger scales (e.g., the whole crystal mush) within the oceanic crust. © 2021 Elsevier B.V.
关键词	EBSD analyses Magmatic fabrics Melt migration Oceanic olivine gabbro Plagioclase crystallographic preferred orientation Ultraslow-spreading oceanic crust
英文关键词	Binary alloys; Compaction; Crystals; Extraction; Feldspar; Grain size and shape; Infill drilling; Iron alloys; Iron oxides; Microstructure; Olivine; Plastic deformation; Structural geology; Titanium alloys; Titanium oxides; Crystal plastic deformations; Crystallographic preferred orientations; Grain size variation; Oceanic core-complexes; Rock-forming minerals; Slow-spreading ridges; Southwest Indian Ridge; Ultra-slow spreading; Crystal orientation; Trachinotus falcatus
语种	英语
来源期刊	Tectonophysics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/207973
作者单位	Université de Lorraine, CNRS, CRPG, Nancy, France; Dipartimento di Scienze della Terra e dell'Ambiente, Università degli Studi di Pavia, Pavia, Italy; Géosciences Montpellier, Université de Montpellier, CNRS, Montpellier, France; School of Biological, Environmental, and Earth Sciences, University of Southern MississippiMS, United States
推荐引用方式 GB/T 7714	Ferrando C.,Basch V.,Ildefonse B.,et al. Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR)[J],2021,815.
APA	Ferrando C..,Basch V..,Ildefonse B..,Deans J..,Sanfilippo A..,...&France L..(2021).Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR).Tectonophysics,815.
MLA	Ferrando C.,et al."Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR)".Tectonophysics 815(2021).