scholarly journals Metasomatic replacement of diopside by enstatite: a mechanism to convert a lherzolite protolith to orthopyroxene-rich harzburgite

2019 ◽  
Keyword(s):  
Metasomatic Replacement

scholarly journals A Trace Element Classification Tree for Chalcopyrite from Oktyabrsk Deposit, Norilsk–Talnakh Ore District, Russia: LA-ICPMS Study

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 716 ◽  
Author(s):  
Alexander E. Marfin ◽  
Alexei V. Ivanov ◽  
Vera D. Abramova ◽  
Tatiana N. Anziferova ◽  
Tatiana A. Radomskaya ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
General Feature ◽  
Classification Tree ◽  
Global Scale ◽  
Inductively Coupled ◽  
Ore Minerals ◽  
Plasma Mass Spectrometry ◽  
Ore Types ◽  
Metasomatic Replacement ◽  
Ore District

The Oktyabrsk PGE-Cu-Ni deposit is one of the largest resources in the Norilsk–Talnakh ore district, Russia, and it is viewed as an ore giant on a global scale. It contains three types of ores: massive, disseminated and veinlet-disseminated. The two former ore types were formed by a liquation process, whereas the latter was associated with fluid-induced selective metasomatic replacement of metamorphosed wall rocks. One of the major ore minerals in all ore types is chalcopyrite. In this study, we determined concentrations of trace elements in this mineral using laser ablation inductively coupled plasma mass spectrometry. It appeared that standard geochemical tools, such as plotting the data in the form of diagrams of normalized concentrations, binary and ternary plots, do not allow one to distinguish chalcopyrite from visually and genetically different ore types. In contrast, more advanced statistical methods such as cluster analysis show different groupings of elements for each ore type. Based on the element clustering, a classification tree was suggested, which allowed for the differentiation of massive, disseminated and veinlet-disseminated ore types of the Oktyabrsk deposit by Se, Te, Cd and Pb concentrations in chalcopyrite with a success rate of 86%. The general feature is that chalcopyrite of veinlet-disseminated ore is poorer in these elements compared to chalcopyrite of the two other ore types. Chalcopyrite of massive ore is poorer in Se and Te when compared to chalcopyrite of disseminated ore.

scholarly journals The deformation and granitisation of Ketilidian rocks in the Nanortalik area, S. Greenland

1966 ◽  
Vol 59 ◽  
pp. 1-102
Author(s):  
A Escher
Keyword(s):  
Volcanic Rocks ◽  
Time Interval ◽  
Chemical Analyses ◽  
Intrusive Body ◽  
Major Phase ◽  
Fine Grained ◽  
Field Evidence ◽  
Rigid Mass ◽  
Metasomatic Replacement ◽  
Subsequent Replacement

The Nanortalik peninsula, situated between the fjords of Tasermiut and Sarqâ, is largely composed of Ketilidian schists, quartzites and volcanic rocks. All these rocks are more or less strongly folded. The folding took place probably in three successive phases during the Ketilidian period : A first deformation resulting in folds with NNE trending axes, was followed by a second major phase of folding with NW axes. This second folding was essentially plastic. A third deformation, acting probably on a more rigid mass, was characterised by the formation of fracturec1eavage. Third-period folds possess very long wavelengths; their axes are oriented NNE to NE. Migmatisation started probably during the second deformation period resulting in the formation of many dykes and veins of pegmatite and aplite. Four generations of Ketilidian pegmatites can be recognised. Most of them appear to have been formed by metasomatic replacement. It seems that during the Ketilidian orogeny, the evolution of the schists and gneissic schists tended to a granodioritic composition. Potassium metasomatism only became active at the end of the Ketilidian period. In the NE part of the Nanortalik peninsula, three Sanerutian granites can be observed. These granites are similar in composition (quartz-microline-biotite), but possess different ages and textures. The time interval between the last Ketilidian deformation and the emplacement of the first Sanerutian granite was marked by the intrusion of several metadoleritic dykes. The first and principal Sanerutian granite usually shows an indistinct foliation due to numerous oriented inc1usions. Field evidence indicates that this granite was formed mainly by replacement of volcanic rocks. Chemical analyses show that large amounts of K, Si and Na have been supplied to produce the granitisation of the volcanic rocks. The second Sanerutian granite is characterised by a coarse porphyroblastic texture and appears to have been emplaced partially by the intrusion of a melt and partially by a subsequent replacement of the host-rock. Finally, the last Sanerutian granite displays all the characteristics of a pure intrusive body. It is generally very fine-grained and forms many cross-cutting dykes.

Paragenesis of the metasomatic actinolite-bearing rocks from the Khetri copper belt, Rajasthan, India

1967 ◽  
Vol 36 (277) ◽  
pp. 22-28 ◽  
Author(s):  
S. P. Das Gupta
Keyword(s):  
Amphibolite Facies ◽  
Granitic Rocks ◽  
The South ◽  
Sulphide Mineralization ◽  
South Eastern ◽  
Pale Pink ◽  
Mineral Assemblages ◽  
Metasomatic Fluid ◽  
Metasomatic Replacement ◽  
Khetri Copper Belt

SummaryIn the south-eastern part of the Khetri copper belt, actinolite occurs in association with alteration assemblages resulting from the Fe-Mg metasomatism that accompanied sulphide mineralization, and more commonly with albite-bearing rocks formed by albitization of quartzites and schists near granitic rocks. Within the latter occur many coarse, massive, and unoriented aggregates of actinolite crystals, individuals being commonly more than 10 cm long. Locally fluorite-bearing veins oecur within granitic and albite-quartz rocks. The actinolite is pleochroic from pale pink to green; γ: [001] = 26°; γ = 1·642 ± 0·003; 2Vα = 80°. The composition of the analysed actinolite closely compares with those published in the literature excepting in (OH), which is low. The mineral assemblages, formed by metasomatic replacement of pre-existing rocks, are equivalent to those of albite-epidote-amphibolite facies. The metasomatic fluid was apparently rich in Ca, F (indicated by fluorite), and oxygen (indicated by magnetite, ilmenite, and hematite).

Iron oxide - copper - gold-type and related deposits in the Manitou Lake area, eastern Grenville Province, Quebec: variations in setting, composition, and style

2005 ◽  
Vol 42 (10) ◽  
pp. 1829-1847 ◽  
Author(s):  
T Clark ◽  
A Gobeil ◽  
J David
Keyword(s):  
Iron Oxide ◽  
Meteoric Water ◽  
Active Faults ◽  
Rare Metal ◽  
Lake Area ◽  
Rare Metals ◽  
Grenville Province ◽  
Copper Gold ◽  
Radioactive Minerals ◽  
Metasomatic Replacement

The Manitou Lake area (Kwyjibo and Lac Marmont sectors), located in Quebec's eastern Grenville Province, contains magnetite-rich deposits with variable morphological, mineralogical, and chemical characteristics. Most Kwyjibo sector deposits are rich in Cu, rare-earth elements (REE), Y, P, F, and Ag and are anomalous in Th, U, Mo, W, Zr, and Au, and Lac Marmont sector deposits are commonly poor in these elements. Deposits occur in or are closely associated with 1175–1168 Ma leucogranite. They contain combinations of magnetite, clinopyroxene, blue–green hornblende, titanite, apatite, fluorite, quartz, biotite, andradite, epidote, albite, hematite, sulfides (chalcopyrite, pyrite, pyrrhotite, molybdenite, sphalerite), ilmenite, allanite, and other REE-bearing minerals. Veins and breccias are common. Most of the magnetite mineralization was preceded by potassic metasomatism (microcline) and was followed by most of the sulfides and radioactive minerals. Nearby sulfide-dominant deposits may be related. The deposits were formed by metasomatic replacement and fracture filling from hydrothermal fluids of variable composition, which were probably channeled in major, active faults. Oxygen-isotope data from magnetite-rich rocks suggest that fluids were predominantly magmatic and (or) metamorphic and that, locally, mixing with cooler meteoric water may have facilitated precipitation of sulfides and rare-metal minerals. Titanites in mineralized rock have been dated at 972 ± 5 Ma, but most magnetite may be older. Mineralization was syn- to post-tectonic and occurred in an orogenic to orogenic-collapse setting. The Cu–REE–Y-rich deposits are similar to iron oxide – copper – gold (IOCG) Olympic Dam type deposits, and copper- and rare-metals-poor occurrences resemble magnetite ± apatite Kiruna-type deposits.

The phosphate mineral association of the granitic pegmatites of the Fregeneda area (Salamanca, Spain)

1996 ◽  
Vol 60 (402) ◽  
pp. 767-778 ◽  
Author(s):  
E. Roda ◽  
F. Fontan ◽  
A. Pesquera ◽  
F. Velasco
Keyword(s):  
Internal Structure ◽  
Minority Group ◽  
Transformation Mechanism ◽  
Mineral Association ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Phosphate Mineral ◽  
Intermediate Degree ◽  
Metasomatic Replacement

AbstractIn the Fregeneda area different pegmatitic types can be distinguished on the basis of their mineralogy, internal structure and field relationships. The most common type corresponds with simple pegmatites with a homogeneous internal structure, but Li and Sn-bearing pegmatites are also relatively widespread, besides a minority group of Fe-Mn phosphate-bearing pegmatites that has recently been characterized. These pegmatites are located in an intermediate zone, between the barren pegmatites and the most evolved Li and Sn-bearing bodies, and they carry a complex association of phosphate minerals. The study of these phosphates has allowed the identification of the primary phases as wyllieite, graftonite, sarcopside, triplite-zwieselite and ferrisicklerite; the secondary phosphates are rosemaryite, heterosite-purpurite, alluaudite and väyrynenite. In this study, the main characteristics of these phosphate minerals are reported, including their chemical composition, analysed by electron microprobe, and their unit-cell parameters, calculated using X-ray powder diffraction techniques.A common transformation mechanism in this phosphate association is the oxidation of the transition metal cations at the same time as Na-leaching in wyllieite to generate rosemaryite, and Li-leaching in ferrisicklerite to generate heterosite. The occurrence of sarcopside lamellae in ferrisicklerite and heterosite is evidence of the replacement processes of the former by the latter. A Na-metasomatic replacement of the early phosphates as ferrisicklerite and graftonite, producing alluaudite, is also a well developed process.Phosphate minerals occur in pegmatites with an intermediate degree of fractionation, appearing between the barren and the more evolved pegmatites with Li and Sn, which is in agreement with the pegmatite field zonation established in the literature.

scholarly journals Metasomatic Replacement of Albite in Nature and Experiments

Minerals ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 214 ◽  
Author(s):  
Kirsten Drüppel ◽  
Richard Wirth
Keyword(s):  
Metasomatic Replacement
Sign in / Sign up

Export Citation Format

Share Document