Volcanic rocks and several gabbroic units were sampled from outcrops at the localities indicated in fig. The reason is that these rocks form as cumulates by segregation of solid crystals from magma, and not by solidification of the magma itself. Metamorphism of mafic, calcareous and ultramafic rocks content writer. Equigranular garnet, porphyroclastic garnet, and megacrystic garnet pyroxenites. Metamorphic ultramafic rocks represent the largest volume of rocks of the planet. The succession began with the emplacement of a body of coarsegrained biotite pyroxenite with a core of coarsegrained biotitite, which is considered to have formed from the. Understanding the physical properties of ultramafic rocks is important for evaluating a wide variety of petrologic models of the oceanic lithosphere, particularly upper mantle and lower crust. Metamorphism of mafic, calcareous and ultramafic rocks. Processes and ore deposits of ultramaficmafic magmas through space and time focuses on the fundamental processes that control the formation of ore deposits from ultramaficmafic magmas, covering chromite, platinumgroup element pge, nisulfides and tivbearing magnetite. These rocks generally contain high amounts of fe and trace metals such as cr and ni alexander et al. Ultramafic metamorphic rocks result from the metamorphism of mantle rocks and some oceanic crust and contain dominantly magnesium, silicon, and carbon dioxide, with smaller amounts of iron, calcium, and aluminum. Metamorphic evolution of garnetbearing ultramafic rocks. An introduction to igneous rocks requires exploration of three core ideas. Parent material of igneous rocks forms from partial melting of rocks magma at surface is called lava general characteristics of magma general characteristics of magma.
The ultramafic rocks undergo continuous recrystallization due to largescale convection in the sublithosphere mantle and as a result of tectonic processes in the lithosphere. Loferski abstract the chromite deposits near red lodge, mont. Statewide investigations of mafic and ultramafic bodies and their associated minerals are scarce. How to classify igneous rocks into ultramafic, mafic. Ultramafic rocks are those containing 18 % mgo and minerals. Petrology and geochemistry of metamorphosed ultramafic. Ultramafic definition of ultramafic by the free dictionary. Ultramafic rocks very low silica contain 85% ferromagnesian minerals intrusive. Lecture notes 3 igneous rocks glendale community college.
Processes and ore deposits of ultramafic mafic magmas through space and time focuses on the fundamental processes that control the formation of ore deposits from ultramafic mafic magmas, covering chromite, platinumgroup element pge, nisulfides and tivbearing magnetite. They are separated from the ultramafic rocks in northwestern oriente by a major structural and. Petrology and geochemistry of metamorphosed ultramafic bodies. Pages in category ultramafic rocks the following pages are in this category, out of total. Petrology of the ultramafic and gabbroic rocks of the.
Our own recent experience with trying to apply the iugs classification scheme to the numerous carbonaterich, melilite free, ultramafic alkaline rocks of west greenland, northern quebec and labrador also highlights the shortcomings of the current scheme. Rare earth elements in ultramafic and mafic rocks and their minerals. Because the maximum length of these streams is 90%, fine or coarse grained. Classification of maficultramafic intrusions in ontario. Pgecoppernickel potential of maficultramafic intrusions. For the purposes of this discussion, ultramafic rocks are considered to be a subset of read more. Based on textural criteria, the garnet clinopyroxenites were divided into three types. However, in the eastem part of oriente province, the ultramafic rocks are more coherent and cover a much larger area. The succession began with the emplacement of a body of coarsegrained biotite pyroxenite with a core of coarsegrained biotitite, which is considered to have formed from the accumulation of alkalies and volatiles near the roof. Komatite so rare were not going to talk about it much ultramafic rocks are not common on earths crust, but they make up most of the are found in the mantle mostly olivine and pyroxene green minerals.
Distribution of ultramafic rocks shown in black, cuba. Petrology of metamorphosed chromitebearing ultramafic rocks. Our revision to the iugs sequential system is highlighted in bold and the quotation marks refer to sections in le maitre 2002. Introduction mafic and ultramafic rocks were drilled at sites 567, 566, 569, and 570 of leg 84 on the landward slope of. In any case, the first ophiolites to have been recovered from the slope of an active margin are those of the drilled mafic and ultramafic rocks of leg 84. Petrology of the ultramafic and gabbroic rocks of the brady.
Contain variable but greater than 10% of both ortho and clinopyroxene, and accessory phases. There has been growing interest in the compositions of hydrated ultramafic rocks and the degree to which these compositions can be used to infer slab fluxes of trace elements at greater depths in subduction zones, including arc source regions see hattori and guillot, 2003. Komatite so rare were not going to talk about it much ultramafic rocks are not common on earths crust, but they make up most of the are found in the mantle. Use features like bookmarks, note taking and highlighting while reading rare earth elements in ultramafic and mafic rocks and their minerals. Represents fertile mantle that has not undergone a melt extraction event. Hydrothermal zones detection using airborne magnetic and gamma ray spectrometric data of mafic ultramafic rocks at gabal elrubshi area, central eastern desert ced, egypt. The reason is that these rocks form as cumulates by segregation of solid crystals from magma, and not by solidification of the magma. It is a continuation of the authors work published in 2010. Early neoproterozoic assembly and subsequent rifting in. Ababitibi, erenglish river, opopatica, ququetico, ucuchi, wawawa, wbwabigoon.
Ultramafic rocks comprised of forty to one hundred percent percent olivine. Early neoproterozoic assembly and subsequent rifting in south. This book presents an extensive overview of literature published globally in the last decades on ree distribution in minor and accessory minerals from various types of ultramafic, mafic, and other plutonic rocks. The oregon department of geology and mineral industries bulletin 95 north american ophiolites has an index map page v which summarizes the. Geochemical study of ultramafic volcanic and plutonic. Classification of maficultramafic intrusions in ontario and. It is important, therefore, to compare the petrology of. Locations of maficultramafic intrusions sampled in this study with major geological subdivisions. Petrology of the ultramafic and gabbroic rocks of the brady glacier nickelcopper deposit, fairweather range, southeastern alaska by glen r. In contextgeologylangen terms the difference between ultramafic and mafic is that ultramafic is geology describing igneous rocks that contain magnesium and iron and only a very small amount of silica, such as are found in the earths mantle while mafic is geology describing rocks, such as silicate minerals, magmas, and volcanic and intrusive. It is important, therefore, to compare the petrology of ultramafic rocks from the midoceanic ridges. Hopkins 1914 presented a descriptive listing of asbestos, talc, and soapstone. An early investigation of the occurrence and mining methods for corundum associated with ultramafic rocks in georgia was performed by king 1894. Volcanic rock of peridotitic or closely related composition.
Processes and ore deposits of ultramaficmafic magmas through. Locations of mafic ultramafic intrusions sampled in this study with major geological subdivisions. Ultramafic rocks are those containing 18 % mgo and rocks dunites, peridotites and metamorphic rocks talc carbonate and serpentinite. Hydrothermal zones detection using airborne magnetic and gamma ray spectrometric data of maficultramafic rocks at gabal elrubshi area, central eastern desert ced, egypt. The mafic rocks of these maficultramafic intrusions are mainly characterized by gabbro and diabase and the ultramafic rocks by the gabbro and diabase, with ophitic texture consisting mainly of plagioclase. The horoman ultramafic rocks are strongly modified by deepseated deformation and recrystallization, and additionally by mylonitization during the upthrusting intrusion into the earths crust. Ultramafic rocks in gabal elrubshi, central eastern desert, egypt. These associations suggest a common derivation, but details of the way that carbonatite magmas might concentrate geochemically scarce metals. Physical geology in our overview of the earth, we found out that earths internal heat combined with other mechanisms causes rocks to melt in the asthenosphere and lithosphere. Ultramafic rocks also referred to as ultrabasic rocks, although the terms are not wholly equivalent are igneous and metaigneous rocks with a very low silica content less than 45%, generally 18% mgo, high feo, low potassium, and are composed of usually greater than 90% mafic minerals dark colored, high magnesium and iron content. The bulk of the mantle rocks, therefore, meet the criteria of metamorphic rocks. The rainy creek complex represents a composite of successive intrusions of igneous rocks emplaced into the precambrian belt series, probably in middle cretaceous time.
Ultramafic rocks in thrust zones of northwestern oriente. Equigranular garnet, porphyroclastic garnet, and megacrystic garnet. Geochemical study of ultramafic volcanic and plutonic rocks. Rocks archean subprovince type plutonic volcanicplutonic metasedimentary highgrade gneiss 500 km studied intrusion 90 o figure 1. Petrology of metamorphosed chromitebearing ultramafic rocks from the red lodge district, montana by patricia j. Rocks formed from lava are extrusive, or volcanic rocks. Hydration of oceanic peridotites results in increasing serpentine content, which affects lithospheric physical properties and the global biogeochemical cycles of various elements. Pyroxenitic komatiites olivine less abundant and subcalcic augite more plentiful.
Metamorphic evolution of garnetbearing ultramafic rocks in. The exploration, exploitation and use of these magmatic ores are. An igneous rock with a very low silica content and rich in minerals such as hypersthene, augite, and olivine. The ultramafic rocks from oceanic regions may possibly be equivalent to the ultramafic rocks of ophiolite complexes e. This is actually a pretty rare occurrence, and would lead us to believe that mafic and ultramafic rocks should be fairly uncommon.
The oregon department of geology and mineral industries bulletin 95 north american ophiolites has an index map page v which summarizes the locations of ophiolites in north america. Apr 28, 2020 when there are red flags about anything, and in this case plenty of them are associated with the covid19 virus, then i am always going to suspect wrongdoing. Processes and ore deposits of ultramaficmafic magmas. Ultramafic rocks are all plutonic rocks, there are no volcanic counterparts, as there are for rocks that are classified in the qapf diagram. The rizhao hujialin area is located in the central sulu ultrahighpressure orogenic belt, where garnet clinopyroxenite is exposed in the upper part of an ultramafic rock complex and serpentinized dunite is exposed in its lower part. The relative abundances of the rareearth elements ree and high field strength elements hfse remain fairly constant throughout the ultramafic series, and the lower. Formation, classification, and identification of igneous rocks next. Minor and accessory minerals kindle edition by lesnov, felix p download it once and read it on your kindle device, pc, phones or tablets. Rare earth elements in ultramafic and mafic rocks and their. Each of these is introduced simplistically below, and then further explored in other pages of the site. Geosciences free fulltext correlation of elastic moduli. Igneous rock evolution plate tectonics and igneous rock distribution. Ultramafic article about ultramafic by the free dictionary.
Compositional name 0 0 0 0 0 020% 020% 50100% very dark ultramafic. Strict application of the modified classification system requires following the flow chart in fig. Fragments of ash, crystals, pumice, rocks ultramafic peridotite mafic gabbro basalt scoria volcanic tuff intermediate diorite andesite pumice volcanic tuff felsic granite rhyolite obsidian pumice volcanic tuff if an intrusive igneous rock has extremely large minerals 2 inches. Petrology of metamorphosed chromitebearing ultramafic. The exploration, exploitation and use of these magmatic ores are important aspects of geology and. Igneous rocks form as molten rock cools and solidifies general characteristics of magma.
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