نتایج جستجو برای: alkali olivine basalt
تعداد نتایج: 22347 فیلتر نتایج به سال:
a r t i c l e i n f o chemostratigraphy of two contrasting Deccan Traps weathering profiles – an ancient, deeply weathered laterite, and a younger (Quaternary), more moderately weathered saprolite – are used to reconstruct different aspects of basalt weathering. Precision of the HFSE analyses is demonstrated through a report of the long-term concentrations and ratios determined in United States...
[1] We report on ages derived from impact crater counts for exposed mare basalt units in the northern part of the lunar nearside hemisphere (Mare Frigoris), the eastern and northeastern part of the nearside hemisphere (Lacus Temporis, Joliot, Hubble, Goddard, Mare Marginis, and Mare Smythii), the central part of the nearside hemisphere (Palus Putredinis, Mare Vaporum, and Sinus Medii), and the ...
The Kahak- Abbasabad Eocene magmatic belt is situated in the northeast edge of Central Iran Zone and extended from Davarzan in the west of Sabzevar to Mayamey in the east of Shahrood. Rock units of the study area include an alternation of basic- intermediate volcanic rocks (olivine basalt, basalt, Trachybasalt, trachyandesitic basalt, trchyandesite and andesite) and pyroclastic–sedimentary rock...
Jeju Island, South Korea, is a Cenozoic intraplate volcano located in East Asia. The basalts display ocean island basalt (OIB)-like trace element patterns and enriched mantle type 2 (EM2) radiogenic isotope compositions, but the source that remains unclear. Here we report new geochemical compositions of xenoliths, including first helium analysis olivine phenocrysts to constrain basalt. Olivines...
Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic o...
Abstract Background Three stages of basalt weathering are known: early or incipient weathering, intermediate and advanced weathering. The Late Oligocene Gebel Qatrani in Fayum Depression, Egypt, shows signs particularly exhibited spheroids found at the top flow. present paper gives results detailed petrographical, mineralogical geochemical study these spheroids. Results core-stones composed phe...
It is widely accepted that the lithospheric mantle under the North China craton (NCC) has undergone comprehensive refertilization due to input from surrounding subducted slabs. However, the possible contribution from the Paleo-Asian oceanic slab to the north is poorly constrained, largely because of the lack of convincing evidence for the existence of this slab under the NCC. We report here car...
[1] The surface materials of Acidalia and Chryse planitiae, Mars, have been variably interpreted morphologically as basalt and compositionally as andesite or altered basalt. A thorough survey using the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) near‐infrared spectrometer reveals olivine and high‐calcium pyroxene signatures in the shallow subsurface exposed by impact craters. T...
Experimental petrology and major element chemistry are used to infer the melting processes that operate in the upper oceanic mantle to yield basaltic magma, and the subsequent cooling processes by which these magmas chill to form the oceanic crust. THE PRIMARY MAGMAS OF MID-OCEAN RIDGE BASALTS This paper reports experiments carried out between 9 and 16 kbar (0.9 1.6 GPa) using natural, primitiv...
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