FN Archimer Export Format
PT J
TI Multi-scale development of a stratiform chromite ore body at the base of the dunitic mantle-crust transition zone (Maqsad diapir, Oman ophiolite): The role of repeated melt and fluid influxes
BT 
AF ROSPABé, Mathieu
   CEULENEER, Georges
   GRANIER, Nicolas
   ARAI, Shoji
   BORISOVA, Anastassia Y.
AS 1:1,2;2:1;3:1;4:3;5:1,4;
FF 1:;2:;3:;4:;5:;
C1 Univ Toulouse, CNRS, IRD, GET,Observ Midi Pyrenees, 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.
   Kanazawa Univ, Coll Sci & Engn, Dept Sci, Kanazawa, Ishikawa 9201192, Japan.
   Lomonosov Moscow State Univ, Geol Dept, Moscow 119899, Russia.
C2 UNIV TOULOUSE, FRANCE
   JAMSTEC, JAPAN
   UNIV KANAZAWA, JAPAN
   UNIV LOMONOSOV MOSCOW STATE, RUSSIA
IF 3.39
TC 17
UR https://archimer.ifremer.fr/doc/00773/88507/94284.pdf
LA English
DT Article
DE ;Oman ophiolite;Chromite;Stratiform chromitite;Melt hybridization;Dunitic mantle-crust transition zone
AB A stratiform chromite ore body crops out in the lower part of the dunitic mantle-crust transition zone (DTZ) that developed at the top of a mantle diapir in the Maqsad area in the Oman ophiolite. It is made of layers ranging in thickness from a few mm to a maximum of 3 m, and in modal composition from massive to antinodular and disseminated ore. The ore body is about 50 m thick and its lateral extent does not exceed several hundred meters. The layering dips gently to the southeast, parallel to that of the overlying gabbroic cumulates. The chromite composition is typical of a MORB kindred - moderate XCr (100 x Cr/(Cr + Al) atomic ratio), ranging from 48 to 60, and relatively high TiO2 content, ranging from about 0.3 to 0.5 wt% -, a characteristic shared by most lithologies issued from the igneous activity of the Maqsad diapir. The silicate matrix is essentially made of slightly serpentinized olivine with minor clinopyroxene and rare pargasitic amphibole, orthopyroxene and garnet. This strongly contrasts with the nature of the mineral inclusions mostly made of the assemblage amphibole-orthopyroxene-mica, enclosed in the chromite grains and represented in abundance all along the ore body whatever the ore grade. The inclusions demonstrate the involvement of a silica- and water-rich melt and/or fluid, in addition to MORB, in the early stages of chromite crystallization. The chemical composition of chromite, silicate matrix, together with the one of silicate inclusions display well-defined evolutions vertically along the stratiform chromitite. At the scale of the ore body, the compositional trends are independent of the ore concentration but the major kinks in these trends are well-correlated with levels of magmatic breccias. This shows that abrupt chemical changes can be attributed to sudden melt fluids injection events followed mainly by melt-fluid-rock interaction and in a lesser extent by quieter evolution by fractional crystallization. At the thin section scale, second order chemical variations, essentially in the Mg# (100 x Mg/(Mg + Fe2+) atomic ratio) of chromite and Fo of olivine, are clearly attributable to re equilibration between these two solid phases, possibly in the presence of an interstitial melt/fluid. 
PY 2019
PD DEC
SO Lithos
SN 0024-4937
PU Elsevier
VL 350
UT 000504504700008
DI 10.1016/j.lithos.2019.105235
ID 88507
ER

EF