FN Archimer Export Format
PT J
TI Melt hybridization and metasomatism triggered by syn-magmatic faults within the Oman ophiolite: A clue to understand the genesis of the dunitic mantle-crust transition zone
BT 
AF ROSPABé, Mathieu
   BENOIT, Mathieu
   CEULENEER, Georges
   KACZMAREK, Mary-Alix
   HODEL, Florent
AS 1:1,2;2:1;3:1;4:1;5:1;
FF 1:;2:;3:;4:;5:;
C1 Univ Toulouse, CNRS, IRD, Observ Midi Pyrenees,GET, 14 Ave E Belin, F-31400 Toulouse, France.
   Japan Agcy Marine Earth Sci & Technol JAMSTEC, Res Inst Marine Geodynam IMG, 2-15 Natsushima, Yokosuka, Kanagawa 2370061, Japan.
C2 UNIV TOULOUSE, FRANCE
   JAMSTEC, JAPAN
IF 4.823
TC 18
UR https://archimer.ifremer.fr/doc/00773/88514/94283.pdf
LA English
DT Article
DE ;Oman ophiolite;dunitic mantle-crust transition zone;syn-magmatic faulting;melt-rock reactions;high temperature hydrothermalism;melt hybridization
AB On Earth, most of the critical processes happen at the frontiers between envelopes and especially at the Moho between the mantle and the crust. Beneath oceanic spreading centers, the dunitic transition zone (DTZ) appears as a major interface between the upwelling and partially molten peridotitic mantle and the accreting gabbroic lower crust. Better constraints on the processes taking part in the DTZ allows improved understanding of the interactions between silicate melts and hydrated fluids, which act competitively to generate the petrological Moho. Here we combine mineral and whole rock major and trace element data with a structural approach along three cross-sections up to 300 m thick above the fossil Maqsad mantle diapir (Oman ophiolite) in order to understand the vertical organization of the DTZ with depth. Our results highlight that most of the faults or fractures cross-cutting the DTZ were ridge-related and active at an early, high temperature magmatic stage. Chemical variations along the cross-sections define trends with a characteristic vertical scale of few tens of meters. There is a clear correlation between the chemical variation pattern and the distribution of fault zones, not only for fluid-mobile elements but also for immobile elements such as REE and HFSE. Faults, despite displaying very limited displacements, enhanced both melt migration and extraction up to the crust and deep hydrothermal fluids introduction down to the Moho level. We propose that these faults are a vector for upwelling melt modification by hybridization, with hydrothermal fluids and/or silicic hydrous melts, and crystallization. Infiltration of these melts or fluids in the country rock governs part of the gradational evolutions recorded in composition of both the olivine matrix and interstitial phases away from faults. Finally, these faults likely control the thermal structure of the mantle-crust transition as evidenced by the spatial distribution of the crystallization products from percolating melts, organizing the transition zone into pure dunites to impregnated dunites horizons. In this context, the DTZ appears as a reactive interface that developed by the combination of three primary processes: tectonics, magmatism and deep, high temperature hydrothermal circulations. Accordingly, these features fundamentally contribute to the variable petrological and geochemical organization of the DTZ and possibly of the lower crust below oceanic spreading centers, and may be a clue to interpret part the heterogeneity observed in MORB signatures worldwide. 
PY 2019
PD JUL
SO Earth And Planetary Science Letters
SN 0012-821X
PU Elsevier
VL 516
UT 000470047100009
BP 108
EP 121
DI 10.1016/j.epsl.2019.04.004
ID 88514
ER

EF