نتایج جستجو برای: basaltic composition

تعداد نتایج: 261472  

Journal: :Nature Geoscience 2022

Unlike the other terrestrial planets, Earth has a substantial silica-rich continental crust with bulk andesitic composition. A small number of meteorites compositions have been identified that are thought to be products partial melting chondritic protoliths, mode petrogenesis distinct from Earth’s crust. Here we show, using geochemical analyses, unlike known meteorites, Erg Chech 002 strongly f...

2008
L. Borg A. Gaffney C. Shearer B. Jolliff

Introduction: Crystallization of the lunar magma ocean occurred ~4.4 Ga [e.g., 1-4] and produced three principal magma source regions [5-6]. These sources are characterized chemically by low titanium (Ti), high Ti, and high potassium, rare earth element, and phosphorous (KREEP) abundances. The KREEP component was produced after nearly complete solidification of the magma ocean and is highly enr...

جمشیدی‌بدر, محبوبه, حاجی‌قربانی, شبنم, داودی, زینب, نصرآبادی, محسن,

 Mahmoudabad metamorphic complex is a part of Sanandaj-Sirjan metamorphic zone that cropped out in SE Shahindezh. Metapelites are the main lithology of Mahmoudabad complex and there are restricted exposures of foliated and granoblastic metabasites present in this complex as well. Metabasites of this complex are investigated in this research. Metabasites display amphibole and plagioclase mineral...

Journal: :Proceedings of the Imperial Academy 1934

2003
T. J. McCoy

We review petrologic evidence that the acapulcoites and lodranites formed by < 1 ~01% to probably >20 ~01% whole rock partial melting of a chondritic precursor material. At low degrees of partial melting, only Fe,Ni-FeS cotectic melting occurred. Migration distances for partial melts were short, resulting in the formation of acapulcoites with essentially chondritic troilite and plagioclase cont...

2009
Cin-Ty A. Lee Peter Luffi Terry Plank Heather Dalton William P. Leeman

Article history: Basaltic magmatism is a co Received 31 July 2008 Received in revised form 21 November 2008 Accepted 9 December 2008 Available online 30 January 2009

2011
Bradley R. Hacker Peter B. Kelemen Mark D. Behn

a r t i c l e i n f o Crust extracted from the mantle in arcs is refined into continental crust in subduction zones. During sediment subduction, subduction erosion, arc subduction, and continent subduction, mafic rocks become eclogite and may sink into the mantle, whereas more silica-rich rocks are transformed into felsic gneisses that are less dense than peridotite but more dense than the uppe...

2006
Mark D. Behn Peter B. Kelemen

[1] One process for the formation of continental crust is the accretion of arc terranes at continental margins. A longstanding problem with this model is that although the composition of the continental crust is andesitic, the majority of arc lavas are basaltic. Moreover, those arc lavas that are andesitic tend to be evolved (lower Mg #) compared to the continental crust. Continental crust can ...

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