The alkaline affinities of all the gusev volcanic rocks, as well as their limited patterns of distribution, may suggest a local magmatic source for irvine, backstay. Igneous rocks are formed when molten material from within the earth, called magma, cools down and solidifies forming crystals. On the basis of mode of formation the rocks are divided into three categories. Igneous rocks that cooled on the surface are termed extrusive. The relatively small volume of all known alkaline rock and the small absolute sizes of alkaline bodies had suggested their derivation from the overwhelming subalkaline magmas, but it was not until the hawaiian lavas were closely considered that a promising clue to an explanation was found. Alkaline igneous rocks host deposits of a variety of rare metals and industrial. Alkaline rocks and carbonatites of the world request pdf. Occurrence, texture, and classification of igneous rocks. The hosts are differentiated rocks ranging from nepheline syenites and trachytes to. Alkaline volcanic rocks from the columbia hills, gusev.
Lamprophyre any of a group of dark gray to black intrusive igneous rocks that generally occur as dikes. Rare earth element deposits of alkaline igneous rocks the locations of several prominent ree deposits and advanced exploration targets which are ho st ed i n al kal in e p er alk ali ne ig ne. Origin of basic and intermediate alkaline rocks as bailey 1974 quotes, it is safe that alkali basalts, basanites and nephenilites are primarily of mantle origin page 436. Igneous rocks are formed when rocks are melted and then cooled again. Lllizos, 26 1990 6798 elsevier science publishers b. In the first stage of both hypotheses large piles of basalt are extruded on the earths surface.
Large rocks are broken down very gradually and the smaller pieces are transported by wind, water, and ice. An igneous rock or a part of an igneous rock with a finegrained or aphanitic texture has crystals, but they are too small to recognized with the unaided eye. First determine composition, which is based on mineral content or color, if you cant see minerals. Igneous rocks originated through solidification of molten material either at or below the surface. Alkaline igneous rocks in the neoproterozoic accretionary collisional structure of the yenisei ridge southwestern fram ing of the siberian craton form small. Contrasting origin of postcollisional highk calcalkaline and. The alno complex in central sweden is one of the largest alkaline and. The top diagram is for extrusive rocks and the lower is for intrusive rocks. Igneous rocks that form below the earths surface are called intrusive igneous rocks or plutonic. Then determine the texture of the rock and based on the two, identify t. Alkaline rock complexes in the usgs publications warehouse. Map of wet mountains area showing location of alkaline complexes. Chemical variation, modal composition and classification of granitoids. Some extrusive igneous rocks have finegrained textures.
Mineral and rock guide booked city college of san francisco. This is a pdf of an unedited manuscript that has been accepted for publication. The book is divided into nine chapters and ancillary material. Note that rocks with glassy or pyroclastic textures may be described by the above compositions, but that for these specimens the final rock name must still. Alkaline rock, any of various rocks in which the chemical content of the alkalies potassium oxide and sodium oxide is great enough for alkaline minerals to form. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Pdf rare earth element deposits of alkaline igneous. Alkaline igneous rocks associated with continental rift valleys volcanic alkali olivine basalt trachyte phonolite. Pdf highly evolved alkalineperalkaline igneous rocks host deposits of rare earth elements ree including y as well as zr, hf, nb, ta, u and th. They form when magma enters an underground chamber, cools very slowly, and forms rocks full of large crystals.
Ternary classification of felsic to mafic igneous rocks. Crystallization, fractionation and solidif ication of comagmatic alkaline series sequentially emplaced in the carbonatite complex of tiruppattur, tamil nadu, india 537 changes in structure of residual melts in spatial and temporal conditions. This led to the subdivision of igneous rocks into four categoriesacidic, intermediate, basic, and ultrabasic. Metasomatized ijolite xenoliths from diamond jo quarry ra, j. The calcalkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic. Pdf the mineralogy chemistry tectonic settings and. Pdf rare earth element deposits of alkaline igneous rocks. Texture physical appearance in the rock occur only crystals, so the texture is holocrystalline.
Rare earth element deposits of alkaline igneous rocks. These rocks constitute the first definitive observation of alkaline rocks on mars. Rare earth element deposits of alkaline igneous rocks mdpi. Igneous rocks comprise such types as the common granites which formed from tremendously large masses of molten material intruded from depths of the earth into the crust, then 1. Granites tend to be associated with other igneous rocks plutonic as well as volcanic to. Despite their relatively small volume worldwide, alkaline rocks account for most of the hundreds of rocktype names in the geologic literature because of unusually great variation in chemical, mineralogical, and. The aim of the book is to help students to develop appropriate descriptive and inter. Under high temperature and pressure, the sediment becomes compacted. They are characterized by a porphyritic texture in which. Igneous rocks that form above the earths surface are called extrusive igneous rocks. Y amsterdam alkaline igneous rocks of magnet cove, arkansas. Alkaline igneous rocks host deposits of a variety of rare metals and industrial rocks and minerals. To identify name igneous rocks, you determine two things about the rock.
Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. According to shand 1922, alkaline plutonic rocks should be defined by high alkali contents relatively to silica and alumina, using the cationic ratio 1. This reader emphasizes how all igneous rocks are formed and explores how the formation is related to igneous rock classification. In contrast, extrusive igneous rocks are formed outside the earths crust, when lava cools. Four types of deposits are found in the gallinas mountains. In practice, this means that the average dimension of the crystals is less than 1 millimeter. They are thus characterised by an interlocking crystalline texture. This will lead us into discussions on magma, silicate minerals, and the construction of a useful illustration that may be used to both name an igneous rock and determine its mineral content. Grain size and the proportion of grain sizes the texture is phaneritic equallycrystallized and crystals are medium. Pdf rare metal deposits associated with alkalineperalkaline. Alkaline igneous rocks are so enriched in alkalis that they contain abundant na and kbearing minerals such as feldspathoids, alkali pyroxenes and alkali amphiboles.
Most transitional to midly alkaline nenormative basalts contain peridotite xenoliths, interpreted as evidence for an ultimate mantle origin. Types of rocks and their properties pdf download geography the earths crust is composed of rocks. Igneous rock identification university of washington. The writers study of examples of many alkaline rocks in the collection of the massachusetts institute of technology has shown him that nephelite, when. For porphyry copper deposits in general, the compositions of the shallow intrusions that host porphyry copper deposits indicate that the deep melt reservoirs from which both the shallow intrusions and the ore fluids were derived may be compositionally. Crystallization, fractionation and solidification of co. Other alkaline minerals have a high ratio of alkalies to alumina al 2 o 3, as in aegirine pyroxene and. Volcanic glass is rock that forms when lava cools too quickly to form crystals. The commodities of special economic importance in these rocks are rare earth elements ree. Intrusive igneous rocks form inside the earth, when magma cools. Ansrucr ijolite xenoliths occur in garnetpseudoleucite syenite that forms part of the outer ring. Relations to sedimentary rocks volcaniclastic rocks are common in many districts, but any sedimentary rock may be spatially associated with a porphyry copper deposit. Such minerals may be unusually sodium rich, with a relatively high ratio of alkalies to silica sio2, as in the feldspathoids. Rock identification adapted from don peck page 5 of 16 the rock identification key about the rock identification key this rock key has been designed and written to assist children and adults in identifying the common rocks they find in their back yards and on memorable vacations.
Molten rock inside the earth is called magma, while molten rock on the earths surface is called lava. Unravelling the internal architecture of the alno alkaline and. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma. Representative examples of the rock types found in porphyry copper deposits are listed in table 1. Types of rocks and their properties pdf download geography. Resources alaska department of natural resources, 2010, division of geological and geophysical surveys, alaska geologic materials center website, accessed may 27. Because most igneous rocks are composed of silicate minerals, the earliest chemical classification used was one based on weight percentage of sio 2 in the rock. Alkaline igneous complexes host deposits of rare earth elements ree, which represent one of the most economically important resources of heavy ree and yttrium y. Neoproterozoic alkaline magmatism and associated igneous rocks. Holes in extrusive rocks magma stored underground can. Petrology of the alkaline core of the messum igneous complex. To simplify the discussion we are severely reducing the number of igneous rocks you need to know to an essential few.
These measurements were shifted and merged with additional gravity. Teacher notes if your students have completed the plate tectonic units on volcanoes, they should be familiar with different volcanic environments. Ii occurrence, texture, and classification of igneous rocks gezahegn yirgu encyclopedia of life support systems eolss summary in this article, the manner in which igneous rocks occur in nature is introduced, followed by a discussion of the general textural features and appearance of these rocks. Genesis of the calcalkaline igneous rock suite springerlink. Such minerals may be unusually sodium rich, with a relatively high ratio of alkalies to silica sio 2, as in the feldspathoids. A small amount of bastnaesite, a ree mineral, was recovered during processing for fluorite from the gallinas mountains. These experimental results support two complementary hypotheses for the derivation of the calcalkaline igneous rock suite from the mantle by a two stage igneous process. Igneous rocks and processes revised on 102011 page 5 of 10 finegrained or aphanitic. Alkaline rocks excess alkalis in feldspathoids, sodic. It has a shiny, glasslike surface with small, fine grains.
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