Chromite in the Mantle Section of the Oman Ophiolite: Implications for the Tectonic Evolution of the Oman Ophiolite     

SAVELYEVA G.N.  BATANOVA V.G. 《《地质学报》英文版》2015,89(Z2):77-78

<正>Structure and composition of the Uralian ophiolites reflect a large spectrum of geodynamic environment of their creation during Paleozoic time:from mid-ocean ridge,rift zone in continental margin,and suprasubduction spreading zone(SSZ)with resultant lherzolite or harzburgite ophiolite type(LOT and HOT).Residual  相似文献   

Crustal Evolution of Island-Arc Ultramafic Magma: Galmoenan Pyroxenite-Dunite Plutonic Complex, Koryak Highland (Far East Russia)     

BATANOVA  V. G.; PERTSEV  A. N.; KAMENETSKY  V. S.; ARISKIN  A. A.; MOCHALOV  A. G.; SOBOLEV  A. V. 《Journal of Petrology》2005,46(7):1345-1366

Alaskan-type platinum-bearing plutons and potassium-enrichedmafic to ultramafic volcanic rocks are temporally and spatiallyassociated within the Late Cretaceous–Paleocene Achaivayam–Valaginskiiintra-oceanic palaeo-arc system, allochthonously present inthe Koryak Highland and Kamchatka Peninsula (Far East Russia).The compositions of the parental magmas to the Alaskan-typecomplexes are estimated using the Galmoenan plutonic complexas an example. This complex, composed of dunites, pyroxenitesand minor gabbros, is the largest (20 km³) in the system andthe best studied owing to associated platinum placer deposits.The compositions of the principal mineral phases in the Galmoenanintrusive rocks [olivine (Fo_79–92), clinopyroxene (1–3·5wt % Al₂O₃, 0·1–0·5 wt % TiO₂), and Cr-spinel(5–15 wt % Al₂O₃ and 0·3–0·7 wt %TiO₂)] are typical of liquidus assemblages in primitive island-arcmagmas in intra-oceanic settings, and closely resemble the mineralcompositions in the Achaivayam–Valaginskii ultramaficvolcanic rocks. The temporal and spatial association of intrusiveand extrusive units, and the similarity of their mineral compositions,suggest that both suites were formed from similar parental magmas.The composition of the parental magma for the Galmoenan plutonicrocks is estimated using previously reported data for the Achaivayam–Valaginskiiultramafic volcanic rocks and phenocryst-hosted melt inclusions.Quantitative simulation of crystallization of the parental magmain the Galmoenan magma chamber shows that the compositions ofthe cumulate units are best modelled by fractional crystallizationwith periodic magma replenishment. The model calculations reproducewell the observed mineral assemblages and the trace elementabundances in clinopyroxene. Based upon the estimated compositionof the parental magmas and their mantle source, we considerthat fluxing of a highly refractory mantle wedge (similar tothe source of boninites) by chlorine-rich aqueous fluids isprimarily responsible for both high degrees of partial meltingand the geochemical characteristics of the magmas, includingtheir enrichment in platinum-group elements. KEY WORDS: subduction; platinum-group elements; clinopyroxene; trace elements; fractional crystallization; Alaskan-type plutons  相似文献