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GEOREF RECORD

The conversion tectonics from spreading to subduction; paleostress analysis of dike swarms during the subduction initiation in the Oman Ophiolite

Susumu Umino, Yuki Kusano, Atsushi Yamaji, Takahiro Fudai, Akihiro Tamura and Shoji Arai
The conversion tectonics from spreading to subduction; paleostress analysis of dike swarms during the subduction initiation in the Oman Ophiolite
Geological Society of America Bulletin (November 2019) 132 (5-6): 1333-1343

Abstract

We present paleostress analyses of dike swarms intruded during the subduction initiation in the northern Oman Ophiolite to understand the tectonomagmatic environment. Five swarms of subparallel dikes extending WNW-ESE are 1-5 km in width and are spaced every 5 km N-S. Each swarm has a core of 100% sheeted dikes 1-2 km in width, which emanated from the dunite-wherlite-clinopyroxenite-gabbronorite-diorite-tonalite complexes below and intruded through V1 and into V2 extrusive rocks. Individual dike strikes are varied but generally subparallel to the overall trend of the swarm. Paleostress analyses indicate subvertical sigma (sub 1) , approximately sigma (sub 2) , and subhorizontal sigma (sub 3) with high magma pressures, resulted in the mutually intrusive, extensional shear dikes and abrupt changes in dike strike at high angles. These occurrences suggest intrusions under a more compressive environment compared to the extensional stress field that formed the N-S-striking sheeted dikes of V1 spreading stage. Most E-W-striking dikes possess both boninitic and tholeiitic geochemistry. The latter resemble the V1 flows and dikes with affinities of mid-ocean ridge basalt. Some tholeiitic dikes strike N-S, which are mutually intrusive to E-W-striking dikes. Tholeiitic dikes are more intensely altered than boninite, suggesting their older ages. Conversion of the stress field from a N-S-running spreading axis to inextensional E-W-running rift zones associated with the change in magma geochemistry agree with the relatively compressive V2 arc above a forced subduction zone, which originated from intraoceanic thrusting caused by the clockwise rotation of a microplate including the future northern ophiolite.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 132
Serial Issue: 5-6
Title: The conversion tectonics from spreading to subduction; paleostress analysis of dike swarms during the subduction initiation in the Oman Ophiolite
Affiliation: Kanazawa University, College of Science and Engineering, Ishikawa, Japan
Pages: 1333-1343
Published: 20191112
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 68
Accession Number: 2020-000561
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020015
Illustration Description: illus. incl. 1 table, geol. sketch maps
N24°19'60" - N25°00'00", E56°00'00" - E56°30'00"
Secondary Affiliation: Geological Survey of Japan, JPN, JapanKyoto University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202001
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