Unreferenced date December 2009 Protolith refers to the precursor lithology of a metamorphic rock . For example, the protolith of a slate is a shale or mudstone . Metamorphic rocks can be derived from any other rock and thus have a wide variety of protoliths. Identifying a protolith is a major aim of metamorphic geology. Sedimentary rock s have no protolith because they are made of sediment. However, the source of the sediment is termed its Provenance Science provenance . Igneous rock s have no protolith because they form from magma . Category Petrology petrology stub it Protolito nl Protoliet no Protolitt pl Protolit sv Protolit ... more details
Unreferenced stub auto yes date December 2009 Orphan date December 2009 Argillaceous schist is metamorphic rocks metamorphic rock which exhibits fine laminations of clay materials. Its protolith is argillite . DEFAULTSORT Argillaceous Schist Category Schist Petrology stub ... more details
Expert subject Geology date March 2009 An index mineral is used in geology to determine the degree of metamorphism a rock has experienced. Depending on the original composition of and the pressure and temperature experienced by the protolith parent rock , chemical reactions between minerals in the solid state produce new minerals. When an index mineral is found in a metamorphosed rock, it indicates the minimum pressure and temperature the protolith must have achieved in order for that mineral to form. The higher the pressure and temperature in which the rock formed, the higher the Metamorphic grade grade of the rock. The concept traces its roots to 1912, when G.M. Barrow mapped zones of metamorphism in southern Scotland . Each zone is named for the index mineral that appears in it, e.g. the chlorite zone is named for Chlorite group chlorite . Examples Mudrock , a fine grained sedimentary rock often containing aluminium rich minerals, produces these minerals after being metamorphosed, from low to high grade Zeolite Chlorite group Chlorite Muscovite Biotite Garnet Staurolite Kyanite Sillimanite References Marshak, Stephen. Earth Portrait of a Planet . See also Facies Index fossil Category Mineralogy Category Metamorphic petrology petrology stub he ... more details
which have a protolith of an igneous rock are known as Orthoamphibolites . Para amphibolites ..., and may include more quartz, albite, and depending on the protolith, more calcite aragonite and wollastonite ... s and other poorly sorted sediments. If the amphibolite appears to transgress apparent protolith ... of the original protolith assemblage actinolite pseudomorphically replacing pyroxene is an indication ... lineations may occur. While it is not impossible to have remnant protolith mineralogy, this is rare ... equilibrium mineral assemblages of various protolith rock types consist of Basalt ortho amphibolite ... to a metamorphosed ortho amphibolite with a protolith of diorite , gabbro or other mafic intrusive ... more details
The Bangweulu Block is a craton ic unit that forms part of the Congo craton of central Africa. The Bangweulu Block however consists of Palaeoproterozoic granitoids and volcanics, and is overlain by a Palaeoproterozoic continental sedimentary succession, the Mporokoso Group , and does not preserve much direct evidence of Archaean protolith s. Indirect evidence of an Archaean ancestry for the Bangweulu Block is provided by detrital zircon s within the Mporokoso Group , which indicate a local source area with zircons of 3.2, 3.0. 2.7 and 2.5 Ga, but more importantly, by xenocrystic zircon found in volcanic and granitic Lithology lithologies of the Bangweulu Block, and the area to the West, the Central African Copperbelt Rainaud et al., 2003 , which indicate the presence of a ca . 3.2 Ga terrane called the Likasi Terrane . References Rainaud, C., Master, S., Armstrong, R.A. and Robb, L.J. 2003 A cryptic Mesoarchaean terrane in the basement to the Central African Copperbelt , J. Geol. Soc., London , 160 1 , p. 11 14, Doi 10.1144 0016 764902 087 Category Geology of Africa Category Cratons Geology stub Africa stub lv Bangveulu bloks ... more details
unreferenced date November 2007 Parent rock refers to the original rock from which something else was formed. It is mainly used in the context of soil formation where the parent rock will have a large influence on the nature of the resulting soil. The term is also used in the context of metamorphic rocks where again the parent rock refers to the original rock before metamorphism takes place. Parent Rocks can be sedimentary, igneous or metamorphic. ex. shale becomes slate, granite becomes gneiss etc. In these cases, parent rock may be referred to as the protolith . Parent rock is the main source of soil. This type of soil is also called residual soil. Different parent rocks have different chemical compositions. The Parent Rock is also known as bedrock and is made mostly of solid rocks, there is no weathering occurred there because the roots of the plant can not go that deep. It is the third layer and is underneath Topsoil and Subsoil . The parent rock has little organic matter. See also Parent material Category Petrology geology stub nl Sokkel geologie uk ... more details
This article is about a type of sedimentary rock. For the work by Archimedes , Psammites, see The Sand Reckoner . Psammite Ancient Greek Greek Psammos , Sand is a general term for a sandstone , most often used to describe a metamorphosed rock unit with a dominantly sandstone protolith . An alternative term, more commonly used for unmetamorphosed sediments, is arenite adj arenaceous . Pettijohn ref Pettijohn F.J. 1975 , Sedimentary Rocks , Harper & Row, ISBN 0 96 045191 2 ref gives the following descriptive terms based on grain size, avoiding the use of terms such as clay or argillaceous which carry an implication of chemical composition class wikitable Descriptive size terms Texture Common Greek Latin Coarse Gravel ly Psephite psephitic Rudite rudaceous Medium Sand y Psammite psammitic Arenite arenaceous Fine Clay ey Pelite pelitic Lutite lutaceous References Reflist petrology stub Category Sedimentary rocks de Psammit fr Psammite ka nl Psammiet pl Psamity sr uk vi Psammit ... more details
protolith, and micaceous gneisses of siltstone protolith. The Broken Hill ore deposit is considered ... a function of a potential protolith of exhalative manganiferous chert , metamorphically upgraded to a garnetiferous gneiss, and perhaps some reconsititution of that protolith by metasomatism ... protolith s underlying siltstone protolith sequences in highly disturbed metamorphic terranes ... more details
known as a protolith , and the context pressure, temperature, hydrological features, etc. of its ... the grains making up the protolith change shape and size. The identity of the mineral does not change during this process, only the texture. Recrystallization occurs due to heating of the protolith ... of new minerals with the same chemical formula as the protolith. This involves a rearrangement ... mineral crystals different from the protolith. Chemical reactions digest the minerals of the protolith ... of hot water. During this process mineral of the protolith partially dissolve, diffuse through ... to the protolith, which causes it to shear or bend, but not break. In order for this to happen temperatures ... more details
Unreferenced auto yes date December 2009 Image PhylliteUSGOV.jpg thumb Phyllite Image Fylite micro.jpg thumb Photomicrograph of thin section of phyllite in cross polarised light Phyllite is a type of Foliation geology foliated metamorphic rock primarily composed of quartz , sericite mica , and Chlorite group chlorite the rock represents a gradation in the degree of metamorphism between slate and mica schist . Minute crystals of graphite , sericite, or chlorite impart a silky, sometimes golden sheen to the surfaces of Cleavage geology cleavage or schistosity . Phyllite is formed from the continued metamorphism of slate. The protolith or parent rock for a phyllite is a shale or pelite . Its constituent platy minerals are larger than those in slate but are not visible with the naked eye. Phyllites are said to have a phyllitic texture and are usually classified as having a low grade in the regional metamorphic facies . Phyllite has a good fissility a tendency to split into sheets and will form under low grade metamorphic conditions. Phyllites are usually black to gray or light greenish gray in color. The foliation is commonly crinkled or wavy in appearance. Phyllite is commonly found in the Dalradian metasediments of northwest Isle of Arran Arran . References Unreferenced date July 2010 Commons category Phyllite Category Metamorphic rocks Petrology stub cs Fylit de Phyllit es Filita eu Filita fr Phyllite ko it Fillade ka hu Fillit nl Fylliet ja no Fyllitt pl Fyllit pt Filito sk Fylit sr fi Fylliitti sv Fyllit uk zh ... more details
Cleanup date September 2008 In geology , leucogranites are amongst the youngest intrusions related to anatexis of continental crust anywhere in the world. Leucogranites are commonly found in deformed metapelitic meta graywacke sequences that have been thrusted over basement rock basement s during crustal thickening associated with continental collisions. Several examples include the leucogranites of the High Himalayas, the Avalonia Avalon terrane of Maine, and the Black Hills, South Dakota. Leucogranites are typical examples of S type melts, their composition are strongly influenced by the protolith composition and melt volume depends on the amount of volatiles available during melting and protolith composition Leucogranites are common features of convergent orogeny orogens and consist of rich potassium K2O5.5 wt , Ba400 p.p.m. and Sr 300 p.p.m. , and exhibit low concentrations of Zr 40 ppm , Th 1 ppm and Y 10 ppm . The chondrite normalized dn REE electromagnetic spectrum spectra show that they have a low abundance of LaN20, LuN3 and are moderately fractionated LaN LuN7 . An Eu anomaly is absent or weakly negative. The higher 87Sr 86Sr ratio at 550 Ma 0.7345 compared with the migmatite 0.7164 precludes a direct genetic relationship between leptynitic gneisses and leucogranites at Manali. The chemical and mineralogical compositions of the leuocogranites strongly favour a derivation through fluid absent biotite melting of isotopically distinct but chemically comparable Manali type gneisses. The undersaturation of Zr, Th and REE, a typical feature of leucogranitic melts generated during granulite facies anatexis of psammo pelitic lithologies. Braun et al., 1996 . The source of Leucogranites in the Himalayas are generally ascribed to the aluminous schists and gneisses, partly because of structural relation and partly because of isotopic systematics for Rb, Sr, Nd, O. The monazite and zircon upper intercept ages around 500 Ma of the Zanskar leucogranite clearly indicate ... more details
Image Gliederung der Varisziden in Mitteleuropa.jpg thumb 300px Structural map of central Europe, showing the positions of the Hercynian orogeny Hercynian massif s and the zones in which the basement rocks can be divided. The Mid German Crystalline High or Mid German High is a high tectonics structural high in the Paleozoic geology of Germany . The high forms a northeast southwest oriented zone through Germany, but actual outcrop rock outcrops are sparse since Paleozoic basement geology basement rocks are in most of central Germany overlain by younger sedimentary rock s. The Mid German Crystalline High crops out in the Odenwald , the Spessart , the northern Vosges and some small other massifs. Structure The Mid German Crystalline High forms the northern part of the Saxothuringian Zone of the Hercynian orogeny . To the northwest it is bounded by the Northern Phyllite Zone slightly metamorphism metamorphosed sediments of mid Paleozoic age , part of the Rhenohercynian Zone . Southeast of the Mid German High lies a zone where early to mid Paleozoic sediments of the Saxothuringian Basin crop out, metamorphosed during the Hercynian orogeny. Supposedly, during the mid Paleozoic Devonian and early Carboniferous the Mid German Crystalline High formed an area were not much deposition took place, perhaps an archipelago , between two marine or oceanic crust oceanic basins the Rhenohercynian Basin to the north, the Saxothuringian Basin to the south . Some authors assume the northern basin s oceanic crust subducted beneath the Mid German High. ref For example Ziegler 1990 ref Lithologies The zone consists of Proterozoic orthogneiss es and early Paleozoic volcanic rock volcanic amphibolite s with MORB protolith s and tuff s and sedimentary rock sedimentary pelite s, calcareous schist s and marble s rocks that were metamorphosed at high grade during the Hercynian orogeny up to amphibolite facies . These rocks were intruded by two generations of plutons Silurian to Early Devonian 44 ... more details
or monzogranitic in composition and this is interpreted as the protolith. The gneiss is leucocratic ... banded gneiss of monzogranitic composition, and its protolith is interpreted as a set of monzogranite ... more details
Image Syenite.jpg thumb Syenite Image Nepheline syenite 2005.jpg thumb leucocratic variety of nepheline syenite from Sweden s rnaite Syenite is a coarse grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts 5 . The feldspar component of syenite is predominantly alkaline in character usually orthoclase . Plagioclase feldspars may be present in small quantities, less than 10 . When present, ferromagnesian minerals are usually hornblende amphibole , rarely pyroxene or biotite . Biotite is rare, because in a syenite magma most aluminium is used in producing feldspar. Syenites are usually peralkaline and peraluminous , with high proportions of alkali elements and aluminium. Syenites are formed from alkaline igneous activity, generally formed in thick continental crust al areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting . This is required because potassium is an incompatible element and tends to enter a melt first, whereas higher degrees of partial melting will liberate more calcium and sodium, which produce plagioclase, and hence a granite , adamellite or tonalite . At very low degrees of partial melting a silica undersaturated melt is produced, forming a nepheline syenite , where orthoclase is replaced by a feldspathoid such as leucite , nepheline or analcime . Syenite is not a common rock, some of the more important occurrences being in New England , Arkansas , Montana , New York syenite gneiss es , Switzerland , Germany and Norway . Etymology The term syenite was originally applied to hornblende granite like that of Syene in Egypt , from which the name is derived. Episyenite Episyenite or epi syenite is a term used in petrology to describe to the result of alteration of a Silicon dioxide SiO sub 2 sub rich rock to a more SiO sub 2 sub depleted rock. The process whi ... more details
Image North america basement rocks.png right thumb 250px North America cratons and basement rock. The Slave craton is a Canada Canadian geological formation located in the Northwest Territories and Nunavut . This craton is approximately convert 300000 km2 mi2 in size and forms part of the Canadian Shield . It is dominated by ca. 2.73 2.63 Ga greenstone belt greenstones and turbidite sequence geology sequences and ca. 2.72 2.58 Ga plutonic rock, with large parts of the craton underlain by older gneiss and granitoid units. The cratonic block extends from the Great Slave Lake at about 61 N to Coronation Gulf on the Arctic Ocean at 69 N. It covers Longitude longitudinally the area between about 105 W to 117 W. The Slave includes the Acasta Gneiss which is one of the oldest dated rock units on Earth at 4.03 Ga. The Crust geology crust of the Slave craton is thought to have amalgamated during a 2.69 Ga collision between a proto Slave western basement rock basement complex, known as the Central Slave Basement Complex, and an eastern putative island arc terrane Hackett River along a N S suture geology suture . Along the Acasta River, this basement complex yields protolith ages up to ca. 4.03 Ga. Ages represented by the craton are the Cambrian , Cretaceous , Eocene , Jurassic , Permian and Silurian Siluro Ordovician , based on the craton s known kimberlite s which presently number in the hundreds. See also Mackenzie Large Igneous Province Canadian Shield North American craton References Bleeker, Wouter. 2006 Mineral Resources of Canada A Synthesis of Major Deposit types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods. paper to be published jointly by the Geological Survey of Canada GSC and the Mineral Deposits Division MDD of the Geological Association of Canada. Current online verion http gsc.nrcan.gc.ca mindep synth prov slave index e.php Bleeker, Wouter, Bill davis, John Ketchum, Richard Stern, Keith Sircombe, and John Waldron. 2004 T ... more details
rock mass. Usually this represents the protolith chemistry, which forms distinct mineral ... to protolith compositional banding. Crenulation cleavage is a particular type of foliation. Interpretation ... more details
conditions imposed upon the protolith pre metamorphosed rock . This new mineral that is produced found ... the protolith must have achieved in order for that mineral to form. Lawsonite is known to form ... more details
of the schist protolith, or the calcic remains of thin beds of ocean floor material deposited during less active periods of emplacement of the protolith . Chemical analysis of the schist draws ... more details
by the intrusion of a major dyke swarm . ref name Park Scourian complex The protolith s for the Scourian ... in the terrane is the intrusion of the protolith s to the Scourian gneisses at about 3.0&ndash ... more details
Image Ptigmatite.jpg thumb Ptygmatic folding in migmatite Image Migmatite 2005.jpg thumb Migmatite on the coast of Saaremaa . Migmatite is a rock geology rock at the frontier between igneous rock igneous and metamorphic rock s. They can also be known as diatexite . Migmatites form under extreme temperature conditions during prograde metamorphism, where partial melting occurs in pre existing rocks. Migmatites are not crystallized from a totally molten material, and are not generally the result of solid state reactions. Migmatites are composed of a leucosome , new material crystallized from incipient melting, and a mesosome , old material that resisted melting. Commonly, migmatites occur within extremely deformed rocks that represent the base of eroded mountain chains, typically within Precambrian cratonic blocks. Migmatites often appear as tightly, incoherently folded ptygmatic folds Dike geology dikelets , veins and segregations of light colored granite granitic composition called leucosome , within dark colored amphibole and biotite rich material called the melanosome. The light colored material has the appearance of having been mobilized or molten. Once enough leucosomes join up to form a network and granite is produced, the residual material is known as restite . Textures Migmatite textures are the product of thermal softening of the metamorphic rocks. Schlieren textures are a particularly common example of granite formation in migmatites, and are often seen in restite xenolith s and around the margins of S type granites. Ptygmatic folds are formed by highly plastic ductile deformation of the gneissic banding, and thus have little to no relationship to a defined foliation geology foliation unlike most regular folds. Ptygmatic folds can occur restricted to compositional zones of the migmatite, for instance in fine grained shale protoliths versus in coarse granoblastic sandy protolith. Migmatite and the origin of Granites For migmatised Argillite argillaceous rocks ... more details
File Jack hills etm 1999208.jpg thumb right Satellite image Image JackHills Location.jpg thumb Location of the Jack Hills in Australia The Jack Hills are a range of hills in Mid West Western Australia Mid West Western Australia . They are best known as the source of the oldest material of terrestrial origin found to date zircon s that formed nearly 4 billion years ago. These zircons have enabled ground breaking research into the conditions on earth in the Hadean eon. Geography They are located on the border of the Shire of Murchison and the Shire of Meekatharra , south of the Murchison River Western Australia Murchison River , about 800 kilometres north of Perth, Western Australia Perth . Their gazetted position is coord 26 07 S 117 09 E region AU WA type mountain display inline,title . ref name Gazetteer 271010 Gazetteer of Australia name Jack Hills id 271010 ref Geology The Jack Hills are located in the Narryer Gneiss Terrane of the Yilgarn Craton , Western Australia , and comprise an 80 km long northeast trending belt of Fold geology folded and Metamorphism metamorphosed supracrustal rock s. ref cite web url http earthobservatory.nasa.gov Newsroom NewImages images.php3?img id 17201 title Western Australia s Jack Hills work NASA Earth Observatory newsroom accessdate 2006 04 28 ref Sedimentary siliciclastic rocks, interpreted as alluvial fan River delta delta deposits, are the major lithology. Minor mafic ultramafic rocks and banded iron formation BIF are also found in the sequence. The overall sequence is generally considered to be a granulite gneiss, which has undergone multiple Shear geology deformations and multiple metamorphic episodes. The protolith age of the Narryer Gneiss Terrane is variable, but generally considered to be in excess of 3.6 Ga billion years . Oldest zircons on earth Detrital zircon s with ages greater than 4 billion years old have been found in these rocks, and a 4,404 8 million year old zircon was found at Eranondoo Hill ref cite journal u ... more details
Sanukitoids are a variety of high Mg granitoid found in convergent margin settings. The term sanukitoid was originally used to define a variety of Archean plutonic rock, but now also includes younger rocks with similar geochemical characteristics Shirey & Hanson 1984 Rogers et al. 1985 Stern et al. 1989 Kelemen et al. 2004 . They are called sanukitoid because of their similarity in bulk chemical composition to high magnesium andesite from the Setouchi Peninsula of Japan, known as sanukites or setouchites Tatsumi and Ishizaki 1982 . Sanukite rocks are an andesite characterized by orthopyroxene as the mafic mineral, andesine as the plagioclase , and a glassy groundmass. Rocks formed by processes similar to those of sanukite may have compositions outside the sanukitoid field. The term was originally defined by Stern et al. 1989 to refer to plutonic rocks containing between 55 and 60 weight percent SiO sub 2 sub , with Mg 0.6, Ni 100 ppm, Cr 200 ppm, K sub 2 sub O 1 weight percent, Rb Sr 0.1, Ba 500 ppm, Sr 500 ppm, enrichment in L Rare earth element REE s, and no or minor Europium anomaly Eu anomalies . The term sanukitoid suite includes more evolved rocks derived from sanukitoid through fractional crystallization . Sanukitoids are similar in major and trace element composition to adakite s named for occurrences on the Adak Island in the Aluetian island arc . Both suites are thought to form by melting of a mafic igneous rock protolith that has been metamorphosed to garnet pyroxene eclogite or garnet amphibole assemblages Rapp et al. 1991 Thorkelson & Breitsprecher 2005 . The most common source for sanukitoids is probably the Mantle geology mantle , which has been previously Metasomatism metasomatised by silicate melts derived from the melting of a hot, young, subducting slab. When the oceanic crust is subducted and metamorphosed, it is close to its melting point and a slight increase in temperature may cause melting. These melts are initially high in silica at low melt ... more details
Unreferenced date October 2006 Talc carbonate is a geologic term for a suite of rock and mineral compositions found in metamorphism metamorphic ultramafic rocks. The term refers to the two most common end member minerals found within ultramafic rocks which have undergone talc carbonation or carbonation reactions, talc and the carbonate mineral magnesite . Talc carbonate mineral assemblages are controlled by temperature and pressure of metamorphism and the partial pressure of carbon dioxide within metamorphic fluids, as well as by the composition of the rock. Compositional controls In a general sense, talc carbonate metamorphic assemblages are diagnostic of the magnesium content of the ultramafic protolith . Lower magnesian ultramafic rocks 12 18 MgO as a rule of thumb tend to favor talc chlorite assemblages Medium MgO rocks 15 25 MgO tend to produce talc amphibole assemblages. High MgO rocks with in excess of 25 MgO tend to form true talc magnesite metamorphic assemblages. Thus, the MgO content of a metamorphosed ultramafic rock can be estimated roughly by understanding the mineral assemblage of the rock. Magnesium content determines the proportion of talc and or magnesite and aluminium calcium sodium content determines the proportion of amphibole and or chlorite. Talc Carbonate Minerals Several minerals are diagnostic of talc carbonated ultramafic rocks Talc Chlorite group Chlorite , generally magnesian bluish green Tremolite Cummingtonite Grunerite amphiboles in greenschist facies rocks Anthophyllite Cummingtonite amphibole in weakly carbonated serpentinite at greenschist facies or very rarely, uncarbonated amphibolite facies serpentinites Magnesite , and rarely dolomite in association with amphibolitic compositions At amphibolite facies, the diopside in isograd is reached dependent on carbon dioxide partial pressure and metamorphic assemblages trend toward talc pyroxene and eventually toward metamorphic olivine. Mineral Reactions Serpentinisation of olivine Forst ... more details
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