Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The lab will also acquaint you with the most widely used classification schemes for plutonic rocks, and will give you practice at determining mineral. Igneous rocks and processes introduction igneous rocks comprise the bulk of the crust of the earth. Alkaline igneous rocks in the neoproterozoic accretionary collisional structure of the yenisei ridge southwestern fram ing of the siberian craton form small. Introduction to the formation of igneous rocks, including, extrusive and intrusive rocks. Locations of the alkaline rocks compiled for this study. The calc alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic. Rare earth elements deposits in new mexico 1 rare earth elements deposits in new mexico table of contents abstract 2 introduction 2 mining and exploration of ree in new mexico 4 alkaline igneous rocks 4 carbonatites 7 reethu hydrothermal veins 7 pegmatites 8 placer deposits 8 other reebearing deposits 9. Alkaline igneous rocks host deposits of a variety of rare metals and industrial rocks and minerals. The nbtazrree mineralisation of the motzfeldt alkaline. Hydrothermal activity spatially associated with ultramafic rocks, usually serpentinites, has been observed at several localities proximal. The large age range reflects loss and excess of 40ar during weathering and assimilation of mantlederived 40ar, respectively. Four types of deposits are found in the gallinas mountains. Labs advanced igneous petrology earth, atmospheric.
A deposit model for carbonatite and peralkaline intrusion. Report describing the results of a literature search, a limited chemical analytical program, and visits to three alkalinerock localities intended to establish criteria for determining if a site had uranium resource potential. High resolution aeromagnetic survey used to infer the locations of igneous rock bodies in the area, which are provided in gis data files. The acidic igneous rocks commonly referred to as acid rocks and rarely as acidites comprise those rocks, whatever their origin and whatever level of the crust in which they crystallize, that are sufficiently silicarich to contain modal actual or normative theoretical quartz in quantities of about 10% or more. Highvolume magmatic events in subduction systems introduction subductionrelated magmatic arcs represent immense accumulations of intermediate, calc alkaline igneous rocks and are considered the main factories of continental crust on earth. Find materials for this course in the pages linked along the left. The commodities of special economic importance in these rocks are rare earth elements ree. From southwest to northeast these include the sediments of the gariep group and, respectively, calcalkaline igneous rocks and gneisses of the richtersveld and gordonia subprovinces of the namaqua metamorphic province. Chemical and isotopic data cited are consistent with the generation of the com ponents of calcalkaline igneous rocks and porphyry ore deposits by partial melting of oceanic crustal rocks on underlying subduction zones at the elongate compressire junc. Alkaline rock complexes in the usgs publications warehouse.
Plutonic igneous rocks this lab will introduce you to the variety of plutonic rocks and rock suites. Igneousrockswithmoresodium 3andpotassium3bearingmineralsthannormal. Highvolume magmatic events in subduction systems introduction subductionrelated magmatic arcs represent immense accumulations of intermediate, calcalkaline igneous rocks and are considered the main factories of continental crust on earth. Teacher notes if your students have completed the plate tectonic units on volcanoes, they should be familiar with different volcanic environments. Clicking on the minature thumbprints will allow the diagrams to be shown at a larger size. Iron, like aluminum, is a commonly occurring metallic element, comprising 4. Chemical and isotopic data cited are consistent with the generation of the com ponents of calc alkaline igneous rocks and porphyry ore deposits by partial melting of oceanic crustal rocks on underlying subduction zones at the elongate compressire junc. Other alkaline minerals have a high ratio of alkalies to alumina al 2 o 3, as in aegirine pyroxene and. Sulphur isotopes of alkaline magmas unlock longterm records. The alkalic rocks are here regarded as a category in a classification of igneous rock series. Alkaline igneous rocks many alkaline igneous rocks, typically of syenite or granite composition, have higher table 3. In the modern oceans, the mafic association is found in two specific settings. Metasomatized ijolite xenoliths from diamond jo quarry ra, j.
Petrogenesis of the alkaline igneous rock suites of the. Alkaline rocks constitute less than 1% of all igneous rocks of the. In practice, this means that the average dimension of the crystals is less than 1 millimeter. Enough examples are shown for any new data to be typed. 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. Marsh department of geology, rhodes university, grahamstown, 6140, south africa the early cambrian kuboosbremen igneous province, of northwestern south africa and southern namibia, comprises a series of. Genesis of the calcalkaline igneous rock suite springerlink. Like in igneous and sedimentary rocks, there will be some new terms that.
The alkali basalts of fn are porphyritic rocks with altered olivine and colored. Maliand igneous minerals the first step to understand how mali varies in rocks is to note where common igneous minerals plot on a mali diagram fig. By continuing to use our website, you are agreeing to our use of cookies. This is a pdf file of an unedited manuscript that has been accepted for. Rare metal deposits associated with alkalineperalkaline igneous rocks chapter pdf available april 2016 with 1,051 reads how we measure reads. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. For example, the east sulphur spring suite and the eocene magmatic rocks along the carlin trend are less alkaline. Ansrucr ijolite xenoliths occur in garnetpseudoleucite syenite that forms part of the outer ring. The alkaline igneous intrusions west of the nueces river in uvalde county are part of an igneous province that roughly parallels the balcones fault zone in central texas. A suite is a group of petrogenetically related rocks. Rare earth element deposits of alkaline igneous rocks.
Rare earth elements deposits in new mexico virginia t. Ansrucr ijolite xenoliths occur in garnetpseudoleucite. Pdf report of a meeting of the volcanic studies group of the geological society held at heriotwatt university, edinburgh, on 16 september 1984 find. Alkaline igneous rocks are of great interest as they are one of the main hosts of most igneous rare earth elements ree deposits. Nature of alkalic volcanic rock series springerlink. Intrusive igneous rocks cool slowly and form very large crystals. Sep 16, 2019 locations of the alkaline rocks compiled for this study. Intrusive phases of the kuboosbremen igneous province were emplaced into a wide range of precambrian crustal elements. Pdf the mineralogical diversity of alkaline igneous rocks. Rare earth element deposits of alkaline igneous rocks mdpi. 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. 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, which is low in magnesium and. It could although alkaline rocks are known to be characteristic also be maintained that as the alkaline varieties have the of stable, intraplate environments, it is becoming clear most extreme compositions of all igneous rocks, so an that they also play an important role in the igneous activity concentrated at plate margins.
In the past 25 years, ree have become essential components of modern technologies. Proceedings of the 48th annual forum on the geology of industrial minerals. Geochemistry of the alkaline volcanicsubvolcanic rocks of the. 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. 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. The calcalkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic. This reader emphasizes how all igneous rocks are formed and explores how the formation is related to igneous rock classification. Timescales and mechanisms of plume lithosphere interactions. Most transitional to midly alkaline nenormative basalts contain peridotite xenoliths, interpreted as evidence for an ultimate mantle origin.
Sulphur isotopes of alkaline magmas unlock longterm. On the allen ranch olivine basalts nephelineolivine basalts nephelinite, and melilite nephelinite cut limestone of the austin and anacacho units. Alkaline rocks in the kuboosbremen igneous province, southern namibia. As for most other plutonic rocks, the major carriers of hfse in alkaline igneous rocks are accessory zircon and titanite feti oxides ilmenite or. To simplify the discussion we are severely reducing the number of. Labs advanced igneous petrology earth, atmospheric, and. Age and petrogenesis of volcanic and intrusive rocks in. Such minerals may be unusually sodium rich, with a relatively high ratio of alkalies to silica sio 2, as in the feldspathoids.
Sep 27, 2017 mineralogical characteristics of acid igneous and alkaline rocks ch08. Textures of plutonic rocks university of washington. Objectives university of nairobi personal websites. A plate tectonic model for the origin of porphyry copper deposits. Such minerals may be unusually sodium rich, with a relatively high ratio of alkalies to silica sio2, as in the feldspathoids. Evolution of krich magmas derived from a net veined. According to shand 1922, alkaline plutonic rocks should be defined by high alkali contents relatively to silica and alumina, using the cationic ratio 1. 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. Neoproterozoic alkaline magmatism and associated igneous rocks. Igneous rocks and processes revised on 102011 page 5 of 10 finegrained or aphanitic. The felsic endmember of the suites is feldspathoidbearing syenite.
The processes that lead to the formation of igneous rocks have brought earths water to the surface as well as the atmosphere and the chemicals that make up all of organic life, produced most of its metallic ore. Report describing the results of a literature search, a limited chemical analytical program, and visits to three alkaline rock localities intended to establish criteria for determining if a site had uranium resource potential. Download pdf alkaline rocks free online new books in. The kola alkaline province and the alto paranaiba igneous province apip, discussed in the text, are among the largest alkaline provinces. Peralkaline rocks include those igneous rocks which have a deficiency of aluminium such that sodium and potassium are in excess of that needed for feldspar. Some of the interesting things we are going to learn about these rocks are their many and varied textures. Alpide orogenic belts, are thought to constitute a normal facet of calcalkaline magma tism. The mesoproterozioc 1600 to ma is represented by the namaqua metamorphic complex in the south, which comprises granitic gneisses, metasediments and felsic to mafic instrusions, and by the volcanosedimentary sinclair supergroup of central namibia, with its associated granites e. When the molten rock magma cools and solidifies before it reaches the surface it forms intrusive igneous rock. Igneous rocks igneous rocks form by cooling and crystallization of molten rock molten material residing below earths surface is known as magma, whereas the same material at the surface is called lava. A study of geochemistry through the use of standardised graphs. Occurrence, texture, and classification of igneous rocks.
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. Alkaline rocks in the kuboosbremen igneous province. To simplify the discussion we are severely reducing the number of igneous rocks you need to know to an essential few. Pdf geochemically, the large family of alkaline plutonic rocks both qtzundersaturated and oversaturated compositions can be subdivided into. Tertiary alkaline to subalkaline igneous rocks are found associated with. Other elements enriched in these deposits include manganese. Although small in volume, alkaline igneous rocks are found in a large range of geological settings, including continental rift valleys the main setting, intraplate magmatic provinces with uncertain tectonic settings, and destructive plate boundaries fitton and upton, 1987. Here we give very brief descriptions of most types of terrestrial and lunar igneous rocks, their regional distribution and classification, and examples of their geochemical trends and fingerprints. The typical range of iron concentrations in soils is from 0.
S those results are also reported, with additional information about ongoing study. A few hundred years ago, when geology was just getting started before it got started, really, scientists were naturalists or alchemists, and did all sorts of studies of the natural world. Data derived from the 1994 map latest cretaceous and cenozoic magmatic rocks of alaska compiled by e. A plate tectonic model for the origin of porphyry copper. Estimating the pace at which these giant volumes of magmatic rock were added to the crust and the. 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. The heat and pressure cause the rocks to metamorphose or change to another form. The criteria were applied to various sites in the u.
Alkaline rocks excess alkalis in feldspathoids, sodic. Age of paranaetendeka related alkaline magma tism in paraguay conventional kar wholerock and mineral ages for paraguayan alkaline igneous rocks range from 66 to 183. Carbonatite an igneous rock composed principally of carbonate most commonly calcite, ankerite, andor dolomite, and often with any of clinopyroxene alkalic amphibole, biotite, apatite, and magnetite. E peralkaline acid volcanic rocks of oceanic islands. A small amount of bastnaesite, a ree mineral, was recovered during processing for fluorite from the gallinas mountains. Regrettably, there is no consensus among petrologists as to the precise definition of alkaline rocks, and their classification continues to be challenging. Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. The alkaline igneous centres of eastern uganda comprise a younger tertiary group represented by dissected volcanoes and an older cretaceous. Intrusive rocks become exposed on the earths surface when overlying material is eroded away. Alkaline igneous rocks host deposits of a variety of rare metals and industrial. Pdf the mineralogy chemistry tectonic settings and. The presence of aegerine sodium pyroxene and riebeckite sodium amphibole are indicative of peralkaline conditions. They include two types zvolcanic or extrusive igneous rocks form when the magma cools and crystallizes on the surface of the earth zintrusive or plutonic igneous rocks wherein the magma crystallizes at depth in the earth. In the first stage of both hypotheses large piles of basalt are extruded on the earths surface.
Magmas and igneous rocks magma and igneous rocks igneous rocks are formed by crystallization from a liquid, or magma. The igneous rocks belonging to the remedios formation are basic, felsic to. Alpide orogenic belts, are thought to constitute a normal facet of calc alkaline magma tism. Bureau of geology and mineral resources, openfile geologic map ofgm215. Distribution of alkaline and tholeiitic igneous rocks in the paranaetendeka large igneous province prior to continental breakup. The camgrich carbonatites are technically not alkaline, but are commonly associated with, and thus included with, the alkaline rocks. Ageochemical classification for feldspathic igneous rocks. Igneous rocks formed of cooled lava or volcanic ejecta are common, but most molten material cools below earths surface. Map of wet mountains area showing location of alkaline complexes. Readings advanced igneous petrology earth, atmospheric. The mali value of plutonic rocks is the sum of the mali values of the constituent minerals. Distribution of igneous rocks in medina and uvalde counties, texas, as inferred from aeromagnetic data.