Unusual metasomatites (phyolithites) in the Kolvitskiy gabbro-anorthosite rock mass: composition and structural position
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Abstract:
Complex mineralogical, geochemical, and geological-structural characteristics of a rare collection stone of violet color, phyolithite, in the southwestern part of the Kola Peninsula. This is a metasomatic rock formed under the conditions of brittle deformations on gabbro-anorthosites of the Paleoproterozoic Kolvitskiy rock mass. As a result of potassium metasomatosis, the plagioclase of the initial rocks was replaced by a fine-grained mica aggregate of muscovite-phengite composition with inclusions of Va-aluminoseladonite (up to 20-30 microns). Ba-aluminoseladonite contains 6.6-10.5 % by weight of BaO. Manganese is the only chromophore that accumulates in the rock during metasomatosis. It is manganese that provides the purple-violet color of pseudomorphs of mica according to anorthite. The phyolithites is depleted by REE and has a positive Eu-anomaly. The phyolithites are confined to the areas of fracturing of the north-eastern strike, located in the zone of dynamic influence of the north-western closure of the Onega-Kandalaksha rift of the Riphean age. Other formations (injection conglomerates and lamproites) are also associated with the formation of this structure, which owe their origin to an intense fluid flow.Keywords:
Ilmenite
Metasomatism
Anorthosite
Pseudomorph
Ilmenite ore bodies are deposited within the Precambrian anorthosite body distributed in the Hadonggun and Sancheonggun district, Gyeongsangnamdo. This study tries to identify the occurrence of ilmenite ore body in titanium mine area distributed in Wheolheongri, Okjongmyon, Hadonggun and six mining concession areas (Danseong claim no. 64, 65, 74, 75, 84, 85) in Danseongmyon, Sancheonggun. Wheolheongri ilmenite ore body occurs as vein with about 10~50 m width and 100 m length and shows NNE strike and NW dipping. High grade ore with 20 wt% in this area is distributed in intercumulated anorthosite and is sheared and brecciated. Ilmenite occurring in this type is commonly associated with hornbelnde. Ilmenite ore bodies distributed in Danseonggun, Sancheongmyon are deposited in layered anorthosite. They occur as stratiform with variable width from several and several tens meters. Ilmenite which is disseminated in the matrix is sheared and elongated. This type shows generally low grade ( 1.0~6.0 wt%). The ilmenite ore bodies occur as vein and stratiform, and the former shows higher grade than the latter.
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Anorthosite
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Anorthosite
Lake district
Layered intrusion
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In a detailed study of the area of the Lake Sanford titaniferous magnetite deposits some interesting relations between anorthosite and gabbro came to light. Gabbro can be found grading into the anorthosite, showing the consanguinity of the two rocks, but in a few places the gabbro is intrusive into the already consolidated portions of the anorthosite.
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Size can be used as a criterion to select 18 large (> 1 cm) samples from among 148 melt‐rock fragments of all sizes. This selection provides a suite of large samples which represent the important chemical variants among highland melt rocks; each large sample has enough material for a number of sample‐destructive studies, as well as for future reference. Cluster analysis of the total data base of 148 highland melt rocks shows six distinct groups: anorthosite, gabbroic anorthosite, anorthositic gabbro (“highland basalt”), low‐K Fra Mauro, intermediate‐K Fra Mauro, and high‐K. Large samples are available for four of the melt‐rock groups (gabbroic anorthosite, anorthositic gabbro, low‐K Fra Mauro, and intermediate‐K Fra Mauro). This sample selection reveals two sub‐groups of anorthositic gabbro (one anorthite‐poor with negative Eu anomaly and one anorthite‐rich without Eu anomaly). There is a sharp distinction between those Apollo 16 melt rocks and glasses which have both been classified as “gabbroic anorthosite”.
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Anorthite
Layered intrusion
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Layered intrusion
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High-Al gabbro is reported here for the first time from three anorthosite complexes of Orissa sector of Eastern Ghats Granulite Belt (EGGB). It has distinctly different textural, mineralogical and chemical characters from the anorthosite within which it occurs, and also from the spatially associated Fe, Ti and REE enriched ferrodiorite suite. The high-Al gabbro of EGGB is comparable to similar rocks from other anorthosite complexes in major, trace element compositions and Mg# range (50-58). However, in contrast to the high-Al gabbro of the Laramie Anorthosite Complex (LAC), it does not form the most primitive rock of this association and exhibits negative Eu anomaly (Eu/EU * 0 2 0 6). The Mg enriched composition of the silicates of the high-Al gabbro and higher MgO contents of the associated anorthosite and ferrodiorite of the LAC are other critical differences. Variable composition of the parental melts for these rocks at EGGB and LAC is interpreted Derivation of these aluminous melts by partial melting of basalt under high pressure i s suggested.
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