scholarly journals Mineral Chemistry of Sahneh-Harsin Peridotites; Evidences for Partial Melting on Mantle Peridotite over the Subduction Zone

2018 ◽  
Vol 3 (2) ◽  
pp. 225-240
Author(s):  
Fatemeh Nouri Sandiani ◽  
Hossein Azizi ◽  
◽  
Keyword(s):  
Partial Melting ◽  
Subduction Zone ◽  
Mantle Peridotite ◽  
Mineral Chemistry

Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago

2004 ◽  
Vol 175 (5) ◽  
pp. 443-460 ◽  
Author(s):  
Rodolfo A. Tamayo* ◽  
René C. Maury* ◽  
Graciano P. Yumul ◽  
Mireille Polvé ◽  
Joseph Cotten ◽  
...  
Keyword(s):  
Partial Melting ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
The Philippines ◽  
Island Arc ◽  
Island Arcs ◽  
Geodynamic Evolution ◽  
Wide Range ◽  
Opening And Closing ◽  
Back Arc

Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.

Geochemical evidence for the emplacement of the Whin Sill complex of northern England

1985 ◽  
Vol 122 (4) ◽  
pp. 389-396 ◽  
Author(s):  
R. S. Thorpe ◽  
R. Macdonald
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Partial Melting ◽  
Sedimentary Rocks ◽  
Crustal Contamination ◽  
Mantle Peridotite ◽  
Chemical Characteristics ◽  
Heterogeneous Mantle ◽  
Magma Pulses ◽  
Significant Chemical

AbstractThe Whin Sill comprises a major quartz tholeiite sill of late Carboniferous age underlying an area of c. 5000 km2 and with a volume of c. 200 km3, associated with contemporaneous dykes emplaced within Carboniferous sedimentary rocks in northeast England. New trace element analyses of chilled margins, sill interiors and dykes indicate that the Whin Sill complex magmas show significant chemical variations in terms of the relatively stable trace elements Th, Ce, Y, Zr, Nb and Ni. These data indicate that the complex was fed by a large number of compositionally distinct magma pulses, and that certain of the dykes may have formed feeder channels for the sill. The chemical characteristics of the sill and dyke samples are consistent with derivation by extensive polybaric fractional crystallization of olivine tholeiite magma derived by partial melting of compositionally heterogeneous mantle peridotite and/or crustal contamination of mantle-derived magmas.

Deformation-induced decomposition of enstatite in mantle peridotite and its role in partial melting and chromite ore formation

2017 ◽  
Vol 476 (1) ◽  
pp. 1058-1061 ◽  
Author(s):  
D. E. Saveliev ◽  
V. N. Puchkov ◽  
S. N. Sergeev ◽  
I. I. Misabirov
Keyword(s):  
Partial Melting ◽  
Mantle Peridotite ◽  
Ore Formation ◽  
Chromite Ore ◽  
Induced Decomposition

Melting study of a peridotite KLB-1 to 6.5 GPa, and the origin of basaltic magmas

1993 ◽  
Vol 342 (1663) ◽  
pp. 105-120 ◽  
Keyword(s):  
Partial Melting ◽  
Mantle Peridotite ◽  
Quantitative Information ◽  
Scattered Electron ◽  
Continental Flood Basalts ◽  
Image Technique ◽  
Electron Image ◽  
Partial Melts ◽  
Institute Of Technology ◽  
Source Materials

With a newly established multi-anvil press in the Tokyo Institute of Technology, we have carried out a series of melting experiments on peridotite KLB-1 up to 6.5 GPa. Melt fractions of the peridotite were determined in a wide P-T range using extensive X -ray mapping analysis of run products by EPMA and a digitalized back-scattered electron image technique. Compositions of partial melts and solid residues were determined in the whole melting range up to 6.5 GPa. Given quantitative information on mantle melting, we discuss conditions of melting of various basalt magmas and the nature of their source materials. Our conclusions are consistent with the hypothesis that typical mid oceanic ridge basalts represent low pressure ( ca . 1 GPa), low temperature ( T p ≈ 1300 °C) partial melting products of mantle peridotite. Island arc picritic tholeiites may also be regarded as partial melts of a peridotitic source, at 1-2 GPa pressures and T p ranging from 1400 to 1500 °C. However, proposed primary magmas for Hawaiian tholeiite are difficult to produce by partial melting of typical mantle peridotite at any depth under anhydrous conditions. Source materials for magmas in large hotspots (e.g. Hawaii, Iceland and some continental flood basalts (CFBS)) may be anomalously enriched in FeO and TiO 2 relative to typical upper mantle peridotites such as KLB-1.

The Advocate ophiolite mantle, Baie Verte, Newfoundland: regional correlations and evidence for metasomatismGeological Survey of Canada, Earth Sciences Sector, Contribution 20090211.

2010 ◽  
Vol 47 (3) ◽  
pp. 237-253 ◽  
Author(s):  
Jean H. Bédard ◽  
Monica Escayola
Keyword(s):  
Earth Sciences ◽  
Subduction Zone ◽  
Mineral Chemistry ◽  
Major Elements ◽  
Apparent Absence ◽  
Gold Exploration ◽  
Metasomatic Agent ◽  
Exploration Target ◽  
Chemical Signatures

Mantle rocks of the Advocate ophiolite near Flatwater Pond (Baie Verte, Newfoundland) are dominated by harzburgite tectonites, which are extensively converted to listvenite along the Baie Verte Road fault and represent a potential gold exploration target. Most Advocate harzburgites have forsteritic olivine (Fo90.5 to Fo93) and Cr-spinels, with Cr# (= 100Cr/(Cr + Al)) between 52 and 64 and Mg# (= 100Mg/(Mg + Fe2+)) between 56 and 68. These mineral chemical signatures, together with high whole-rock MgO (46%–48%), low Al2O3 (<1%), and TiO2 (<0.003%), imply the Advocate harzburgites are refractory residues after ca. 25%–35% melting. Cr-spinel compositions of Advocate mantle rocks overlap with Cr-spinels from the mantle rocks of the Point Rousse and Betts Cove ophiolites, with Mg# higher than those of Bay of Islands or Thetford Mines mantle Cr-spinels. Although refractory in terms of major elements and mineral chemistry, Advocate harzburgites contain high La–Ce–Pr–Pb–Nd–Sm–Zr contents suggestive of pervasive metasomatism. Similar geochemical signatures occur in all ophiolitic mantle rocks from the Baie Verte Peninsula examined so far. The enrichments are not consistent with supra-subduction zone syn-melting metasomatism as observed in other Appalachian ophiolites. The apparent absence of visible metasomatic channels in most outcrops suggests that metasomatism occurred before obduction by diffuse percolation, but the nature and origin of the metasomatic agent remain speculative. The similarities of mineral and whole-rock geochemistry imply that all mantle rocks from Baie Verte ophiolites are correlative and may represent remnants of a single obducted slab.

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