The bedrock geology of the naugatuck quadrangle with map. Mineral and rock compositions of mafic enclaves in the morton. Contains a wide variety of rock types including graphitic schist and marble. Bancroft corridor in the central metasedimentary belt of the grenville province, the parker mine is exceptional because. The darker object to the right of the notebook is amphibolite. The protolith of this rock was a quartzofeldspathic granite. Allan kays geology department, university of oregon, eugene, or. Metamorphism, mineral assemblege, and metamorphic rocks. Quartzofeldspathic gneiss bobyarchick and others, 1981. Streckheisen 1976 diagrams reveal that 60 gneisses sampled from 3 transects across structural grain are granitic in composition.
Gneiss is a medium to coarsegrained, semischistose metamorphic rock. Question 15 4 out of 4 points this is a photograph of slickensides along the waterfall canyon trail in the white tanks regional park, just a few miles west of glendale, az. Other bands contain platy or elongate minerals with evidence of preferred orientation. Petrologic evolution of gneissic xenoliths in the voiseys bay. Therefore, the best you can do is to report the chemical composition of the minerals found in the gneiss. Jul 14, 2014 the only catch is that gneiss is a rock and rocks are mixtures of minerals. Then you can start reading kindle books on your smartphone, tablet, or computer no kindle device required. Enter your mobile number or email address below and well send you a link to download the free kindle app. Gneiss is the principal rock over extensive metamorphic terrains. Use late, middle, early for volcanic rocks and times. Comparative geochemistry of migmatized, interlayered. Minerals free fulltext constraints from geochemistry and. Gneiss is a very widespread rock type, especially in the lower parts of the continental crust, but it is also a common rock on the surface in some places scandinavia, canada, and other shield areas where crystalline rocks are not covered by a layer of sedimentary rocks.
Lightgray, fine to coarsegrained, foliated, layered muscovitiebearing quartzofeldspathic gneiss. Deformability characteristics of garnetiferous quartzo. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Gneiss has been defined as a foliated rock formed by regional metamorphism in which granulose bands or lenticles of granular minerals alternate with schistose bands and lenticles of flaky or elongate prismatic minerals. The mineralogy of quartzofeldspathic rocks is generally monotonous. Oneill and others 1996 mapped this unit and termed it xaq. Mineral and rock compositions of mafic enclaves in the morton gneiss, selected studies of archean gneisses and lower proterozoic rocks, southern canadian shield, g. The mediumgrained biotitehornblende bearing quartzofeldspathic gneiss is oldest country. The protolith of this rock was a quartzofeldspathic granite which underwent from gly 205 at university of north carolina, wilmington. Gneiss is said to be a german word meaning sparkling or bright. Petrography of the biotitehornblende bearing quartzofeldspathic. Gneiss is a foliated metamorphic rock identified by its bands and lenses of varying composition, while other bands contain granular minerals with an interlocking texture. Gneiss pronounced nice is a metamorphic rock consisting mostly of quartz and feldspar and showing distinct layering or banding. Pyrometamorphosed quartzofeldspathic rocks sandstone, shale, claystone and sediments sandsilt, clay, glacial till, diatomaceous earth, and their metamorphosed equivalents phyllite, schist.
It is this banded appearance and texture rather than composition that define a gneiss. Plagioclase forms subidioblastic and tabular grains composition determined from maximum. Paragneiss is gneiss derived from sedimentary rock such as sandstone. Information and translations of quartzofeldspathic in the most comprehensive dictionary definitions resource on the web. Gneiss does not have any particular mineral composition, and the term refers only to the banded texture. A glimpse at the buried archean craton of the transhudson orogen article pdf available in canadian journal of earth sciences 362. Sterling igneous suite alaskite gneiss pale pink, orange, or gray, fine to mediumgrained granite gneiss, rarely with porphyroclasts of microclineorthoclase. The proterozoic y terrane of the reading prong of eastern pennsylvania and new jersey consists of lightcolored, sodicrich rocks containing intercalated amphibolite, the losee metamorphic suite, calcarerous and quartzofeldspathic metasedimentary rocks, the intrusive hexenkopf complex, the byram intrusive suite, and quartzpoor monzonite, syenite, and related pyroxene granite. Sutherland2 1 department of geology and mineralogy, the university of adelaide, adelaide, south australia 2 department of geology, the university, leicester, england. Petrography and traceelement geochemistry of the dillon. It does not matter by what process you metamorphose quartz sandstone and limestone, their composition does not change, and they produce the same kind of metamorphic rock. Ramana kk mishra central soil and materials research station central soil and materials research station r. The mineralogy of a particular gneiss is a result of the complex interaction of original rock composition, pressure and temperature of metamorphism, and the addition or loss of components.
It is formed by the metamorphosis of granite, or sedimentary rock. Start studying metamorphism, mineral assemblege, and metamorphic rocks. This page provides mineralogical data about quartzofeldspathic gneiss. The common mineral components are quartz, feldspar, micas, and silicates. The only catch is that gneiss is a rock and rocks are mixtures of minerals. Protolith and tectonic setting of an archean quartzofeldspathic. Although many gneisses are quartzofeldspathic, the mineral composition is not an. Biotite gneiss consists of two main types that regionally occur in near equal abundance. The outer core of the hgd, the xaqf unit, consists of quartzofeldspathic gneiss that is similar to. For example, the outcrop is dominantly quartzofeldspathic gneiss or quartzofeldspathic gneiss crops out throughout the region. Gneiss is a highgrade, metamorphic rock that forms as a result of regional metamorphism. Then you can start reading kindle books on your smartphone, tablet, or computer. Gneiss can be classified on the basis of minerals that are present, process of formation, chemical composition, or probable parent material.
Most gneiss has very a similar composition to granite. It is characterized by alternating light and dark bands differing in mineral composition coarser grained than schist. The regional metamorphic assemblages of the quartzofeldspathic gneisses consist of plagioclase. The mafic gneisses are between the amphibolites and the granitic gneiss in composition and consist of hornblende, biotite, plagioclase, and quartz. Rocks with a more complex chemical composition, such as shale the mineral clay, however, undergo many compositional, and textural changes. Granitegneiss article about granitegneiss by the free. Egypt including humes book and geology of egypt books of rushdi said that were. Such orientations can be interpreted in terms of the stresses that prevailed during the formation of the rock. The parker phlogopite mine, located near notredamedulaus, quebec, 74 km north of ottawa, is well known among mineral collectors for its centimetric euhedral crystals of black spinel. But, as everywhere generally used when no qualifier is prefixed, common gneiss, which is composed of quartz, feldspar and mica, as stated above, is understood, and the term is so employed in this book. Gneiss forming from sedimentary rock is called paragneiss and can form from shale, sandstone or basalt while gneiss forming from igneous rock is called orthogneiss and typically forms from granite, gabbro, or diorite.
The rocks that form gneiss are exposed to extreme pressures and temperatures of between 600 and 700 degrees celsius. Quartzofeldspathic gneisses and metamorphic mafic rocks are the dominant lithologies in the indian creek and ponymiddle mountain. Pdf field geology of highgrade gneiss terrains researchgate. Geochemistry of quartzofeldspathic gneisses and metamorphic. The gneiss family of rocks varieties, uses and mineral make up. Minerals free fulltext a silicocarbonatitic melt and. In the sesia zone of the western alps, italy, early alpine blueschist to eclogite facies metamorphism of rocks of quartzofeldspathic composition has produced the same highpressure assemblage of. If the wider sense is meant the qualifier is given. Gneiss is formed by high temperature and highpressure metamorphic processes acting on formations composed of igneous or sedimentary rocks.
Essential minerals these are minerals that are required within the classification of this rock. Choose from 10 different sets of gneiss flashcards on quizlet. Gneiss rock varies in groups which make their texture different too, like igneous rocks and the sedimentary metamorphosed rocks which fall into various categories like including the quartzofeldspathic, politics and hornblende gneiss. Orthogneiss is gneiss derived from igneous rock such as granite. The bands that form on gneiss rock are due to the various rocks that are a part of its makeup. Definition of quartzofeldspathic in the dictionary. As the pressure and temperature increase, a rock of a given chemical composition is expected to undergo a continuous series of chemical reactions between its constituent minerals and any fluid phase present to produce a series of new mineral assemblages. The layering of a gneiss may be weak or welldeveloped and consists of varying concentrations of biotite, garnet, hornblende, mica, and other minerals. Gneiss rock is further characterized by its alternating light and dark bands of minerals. Many rocks were injected by a granitoid that has blue quartz and augen of potassic feldspar and are arteritic migmatites. The three terms schist, gneiss, and granofels are defined in table 2.
A majority of researchers believe granitegneisses to be granites that have crystallized deep in the earths crust either during the cooling of the magmatic melt under directed pressure or during the process of the magmas movement, as a result of which. Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. The lighter bands contain mostly quartz and feldspar, the darker often contain biotite, hornblende, garnet or graphite. Precambrian research, 3 1976 433462 433 o elsevier scientific publishing company, amsterdam printed in the netherlands comparative geochemistry of migmatized, interlayered quartzofeldspathic and pelitic gneisses. Gneiss granofels and migmatite gneiss and granofels range in composition from felsic to intermediate to mafic. The banding may be oriented nearly parallel to the earths surface horizontal dip or may have a steep dip. We studied gneiss away from and adjacent to dykes and quartzofeldspathic xenoliths in dykes.
The quartzofeldspathic gneiss is formed by the either silicic igneous metamorphosis or rocks such as granite. The reading prong of new jersey and eastern pennsylvania. These temperatures cause the individual minerals to migrate, forming distinct bands through the rock. The dillon quartzofeldspathic gneiss dqg is a thick sequence of conformable microclinerich gneisses that occupy intermediate stratigraphic levels within the exposed section. These igneous suites may represent nearshore phases of the major offshore ophiolite accumulations, and the presence of micaceous quartzofeldspathic sandstones is similar to lithologic associations in some parts of the matakaoa volcanics at east cape pirajno 1980. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Gneiss forms from volcanic rock, shale, or granitic. Paragneiss is gneiss derived from sedimentary rock. Progressive or prograde metamorphism occurs as the temperature and pressure are increased on the rock. Quartzofeldspathic gneiss forms by metamorphosis of either silicic igneous rocks such as granite, rhyolite, and rhyolitic tuff or silicic sedimentary rocks such as sandstone. Deformability characteristics of garnetiferous quartzo feldspathic gneiss rock mass a case study hari dev d. Gneisses of dacitic to rhyolitic composition 6976 weight percent sio2. Sarwade central soil and materials research station central soil and materials research station g. Gneiss displays distinct foliation, representing alternating layers composed of different minerals.
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