نتایج جستجو برای: mafic rocks
تعداد نتایج: 23127 فیلتر نتایج به سال:
Newly discovered xenoliths within Pliocene and Quaternary intermediate volcanic rocks from southern Peru permit examination of lithospheric processes by which thick crust (60–70 km) and high average elevations (3–4 km) resulted within the Altiplano, the second most extensive orogenic plateau on Earth. The most common petrographic groups of xenoliths studied here are igneous or meta-igneous rock...
Kudz Ze Kayah (KZK) and Wolverine are volcanogenic massive sulphide deposits hosted by Early Mississippian meta-rhyolites, marine metasediientmy rocks and intermediate to mafic met&offs of the Yukon Tanana Terrane in the Finlayson Lake area, southern Yukon (Figure 1). This area became a focus of intense exploration in late 1994, following Cominco’s discovery of significant massive sulphides ass...
[1] Spirit’s Mössbauer (MB) instrument determined the Fe mineralogy and oxidation state of 71 rocks and 43 soils during its exploration of the Gusev plains and the Columbia Hills (West Spur, Husband Hill, Haskin Ridge, northern Inner Basin, and Home Plate) on Mars. The plains are predominantly float rocks and soil derived from olivine basalts. Outcrops at West Spur and on Husband Hill have expe...
[1] Spirit’s Mössbauer (MB) instrument determined the Fe mineralogy and oxidation state of 71 rocks and 43 soils during its exploration of the Gusev plains and the Columbia Hills (West Spur, Husband Hill, Haskin Ridge, northern Inner Basin, and Home Plate) on Mars. The plains are predominantly float rocks and soil derived from olivine basalts. Outcrops at West Spur and on Husband Hill have expe...
We compile a 3.7-b.yr.-long time series of ultramafic and mafic rocks including extrusives and shallow intrusives (dikes and sills). We infer that peaks in the time series represent mantle plume events. Rocks erupted from plumes are becoming more Ti rich through time, and several rock types having 118 wt % MgO are Phanerozoic analogs for komatiites. These include meimechites, ankaramites, and r...
The petrography, as well as major and trace element (including rare earth element) compositions of 10 sandstone samples from the Late Proterozoic Buem Structural Unit, southeast Ghana, have been investigated to determine their provenance and tectonic setting. The petrographic analysis has revealed that the sandstones are quartz-rich and were primarily derived from granitic and metamorphic basem...
the area of study is located 120 km north-east of shahrood city. in terms of structure and geological classification, this area is located in the northern part of central iran zone. granitoids of troud ranging from monzonite to granite. the main minerals of granitoids are quartz, plagioclase, and orthose. the accessory minerals are biotite, hornblende, sphene, and opaque minerals. various textu...
The extension of subduction processes into the Eoarchaean era (4.0-3.6 Ga) is controversial. The oldest reported terrestrial olivine, from two dunite lenses within the ∼3,720 Ma Isua supracrustal belt in Greenland, record a shape-preferred orientation of olivine crystals defining a weak foliation and a well-defined lattice-preferred orientation (LPO). [001] parallel to the maximum finite elonga...
Abundant mafic and ultramafic rocks including basalts, komatiitic basalts, and peridotites occur in the Proterozoic Sibao Group, northern Guangxi Province, China. Whereas the basalts are generally pillow lavas, the komatiitic basalts are typically spinifex-textured and, in a few cases, show pyroxene accumulation associated with Ni Cu (PGE) sulfide deposits. The peridotites occur in the lower po...
Astaneh granodiorite intrusion, located at south west of Arak, includes an abundant rounded and rarely ellipsoid microgranular enclaves composed of gabbro, diorite and quartz diorite. The diameter of enclaves ranges from a few millimeters to 40 centimeters. These enclaves are very fine-grained and show chilled margins. The size of crystals decreases gardually from center toword margin. The chil...
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