نتایج جستجو برای: gabbroic composition
تعداد نتایج: 259931 فیلتر نتایج به سال:
Abstract The ~3033 Ma Stella layered intrusion is hosted by supracrustal rocks of the Kraaipan–Madibe greenstone terrane, South Africa. studied portion consists mainly magnetite leucogabbro and anorthosite, as well several massive layers. hosts a laterally continuous, ~60-m-thick, PGE mineralized interval, with total resources amounting to 108t Pt + Pd Au, constituting one oldest known reef-sty...
The existence of ancient rocks in present mid-ocean ridges have long been observed but received less attention. Here we report the discovery of zircons with both reasonably young ages of about 5 Ma and abnormally old ages of approximate 180 Ma from two evolved gabbroic rocks that were dredged from the Southwest Indian Ridge (SWIR) in the Gallieni fracture zone. U-Pb and Lu-Hf isotope analyses o...
Introduction: Eucrite meteorites represent earlyformed (~4.557-4.565 Ga) crustal basalts and basaltic to gabbroic cumulates from the howardite-eucritediogenite (HED) parent body or bodies (e.g., [1]). The HED are commonly thought to originate from the asteroid Vesta (e.g., [2-3]), although O-isotopes for eucrites [4] and diogenites [5] indicate more than one parent body. Approximately 85% of eu...
Nature and cause of compositional variation among the alkalic cap lavas of Mauna Kea Volcano, Hawaii
Most Hawaiian basaltic shield volcanoes are capped by moderately to strongly evolved alkalic lavas (MgO < 4.5 wt. %). On M auna Kea Volcano the cap is dominantly composed of hawaiite with minor mugearite. Although these lavas contain dunite and gabbroic xenoliths, they are nearly aphyric with rare olivine and plagioclase phenocrysts and xenocrysts. The hawaiites are nearly homogeneous in radiog...
Physicochemical conditions under which early sulfide saturation occurs and the role of this process in mineralising potential magmas different geodynamic settings have been subject interest many recent studies. Here we present new temperature-pressure-fO2 data on sulfide-saturated magmatic enclaves host lavas from volcanic systems subduction, post-subduction intraplate settings, some are associ...
Carboniferous magmatism in southwestern Iberia was continuously active for more than 60 m.y. during the development of Appalachian-Variscan belt North America, Africa and Western-Central Europe. This collisional orogen that records closure Rheic Ocean is essential to understanding late Paleozoic amalgamation Pangea supercontinent. However, oblique convergence between Laurussia Gondwana lasted f...
Northwest Africa (NWA) 11962 is a lunar regolith breccia composed of wide range different clasts. The origin this meteorite confirmed by oxygen isotope analysis and the Fe/Mn ratio in pyroxene olivine. In present study, clasts matrix NWA are characterized optical electron microscopy along with microprobe analyses micro-Raman spectroscopy. has glassy impact melt matrix, which accounts for 35% su...
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