Polymetamorphic greenschists with Al-rich green spinels (the Western Carpathian Mts.)

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Dušan Hovorka
Keyword(s):  
Thin Section ◽  
Special Interest ◽  
Present Author ◽  
Metamorphic Rock ◽  
Rock Type ◽  
Raw Material ◽  
Metamorphic Rocks ◽  
Material Type ◽  
Rock Types ◽  
Igcp Project

AbstractDuring the course of the UNESCO/IGCP project nr. 442 (1999–2001) the present author, along with several colleagues, has described rare raw material types, used in the Neolithic/Aeneolithic, for the construction of stone implements. A metamorphic rock-type (greenschist) containing a substantial amount of Al-rich green spinels, is of special interest. This raw material type is characterized in this contribution.The rocks, which are the object of the present study, are metamorphic rocks of the greenschist association (containing monoclinic as well as rhombic amphiboles, and Al-rich green spinels in a substantial (5–20 vol. %) amount). Accessory mineralsnot necessarily encountered in each thin section, are olivine, orthopyroxene, corundum, clinozoisite, muscovite, cordierite, various plagioclases (albite and anorthite included), phlogopite, ilmenite, magnetite and sphene. The results of microprobe analyses for individual rock-forming minerals are presented. The genesis of the described rock-types is complicated; they are product of three metamorphic events (M1, M2, M3).

DENSITIES OF METAMORPHIC ROCKS

Geophysics ◽  
1971 ◽  
Vol 36 (4) ◽  
pp. 690-694 ◽  
Author(s):  
Scott B. Smithson
Keyword(s):  
Metamorphic Rock ◽  
Granite Gneiss ◽  
Biotite Granite ◽  
Metamorphic Rocks ◽  
Upper Crust ◽  
Rock Density ◽  
Rock Types ◽  
Crystalline Crust ◽  
The Mean ◽  
Few Data

Although metamorphic rocks comprise a large part of the crystalline crust, relatively few data concerning metamorphic rock densities are available. In this paper, we present rock densities from seven different metamorphic terrains. Mean densities for rock types range from [Formula: see text] for biotite granite gneiss to [Formula: see text] for diopside granofels. Mean rock densities for metamorphic terrains range from 2.70 to [Formula: see text]. Rock density may decrease in the lower part of the upper crust. Most mean rock densities for metamorphic terrains fall between 2.70 and [Formula: see text]; the mean density of [Formula: see text] commonly used for the upper crystalline crust is too low.

scholarly journals Slates: a potential rock type to extract geothermal energy from the underground?

2020 ◽  
Author(s):  
Johannes Herrmann ◽  
Erik Rybacki ◽  
Wenxia Wang ◽  
Harald Milsch ◽  
Bianca Wagner ◽  
...  
Keyword(s):  
Geothermal Energy ◽  
Rock Type ◽  
Metamorphic Rocks ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
The European Union ◽  
Fracture Permeability ◽  
Horizon 2020 ◽  
Rock Types ◽  
Confining Pressures

<p>Commonly used host rock reservoirs for Enhanced Geothermal Systems (EGS) are composed of granite, as they display highly conductive and sustainable fracture networks after stimulation. However, considering the large amount of metamorphic rocks in Europe’s underground, these rock types may also show a large potential to extract geothermal energy from the subsurface. Within the framework of the European Union’s Horizon 2020 initiative ‘MEET (Multi-Sites EGS Demonstration)’, we are conducting fracture permeability experiments at elevated confining pressures, p<sub>c</sub>, temperatures, T, and differential stresses, </p>

Petrology of the ultramafic lamprophyre and associated rocks at Coral Rapids, Abitibi River, Ontario

1994 ◽  
Vol 31 (8) ◽  
pp. 1325-1334
Author(s):  
A. D. Edgar ◽  
L. A. Pizzolato ◽  
G. M. Butler
Keyword(s):  
Rock Type ◽  
Metamorphic Rocks ◽  
Alkaline Rocks ◽  
Rock Types ◽  
Ultramafic Lamprophyre ◽  
Mantle Sources ◽  
Host Rocks ◽  
Uniform Composition ◽  
West Eifel ◽  
Metasomatized Mantle

An ultramafic lamprophyre sill and dikes, and an olivine–melilite-rich dike rock intrude Lower to Middle Devonian sediments and low- to high-grade Archean metamorphic rocks on the west bank of the Abitibi River, Coral Rapids, Ontario. Although previously considered to be kimberlitic, all these rocks contain olivine + clinopyroxene + phlogopite ± melilite, and hence are ultramafic alkaline rocks. The ultramafic lamprophyre can be distinguished from the dike by its lower SiO2, Na2O, Al2O3, and higher MgO and FeO. In contrast the olivine–melilite dike rock has a more uniform composition, characteristically contains melilite, and has higher Cr and Ni contents. Enriched light rare earth element (LREE) chondrite-normalized patterns are similar for all rocks.Olivine, clinopyroxene, and phlogopite have Mg# (Mg# = 100 Mg/(Mg + Fe) mol) typical of minerals in primitive alkaline rocks. Melilite composition is similar to that of igneous melilites. Phlogopites in all rock types are enriched in Ba and F and the degree of enrichment is distinct for each rock type. Accessory minerals include apatite, carbonates, chlorite, sericite, and sodalite (only in the olivine–melilite-bearing rock).The mineralogy and chemistry of the Coral Rapids rocks suggest that they are derived from a primitive olivine melilitite magma that may have evolved by fractionation of small amounts of olivine and clinopyroxene to form these alkaline ultramafic magmas.Xenoliths in the ultramafic lamprophyre sill and in lesser abundance in the olivine–melilite dike rock include olivine, phlogopite, and clinopyroxene-rich mantle-derived assemblages. The similarity between these xenoliths and their host rocks at Coral Rapids and those from southwest Uganda and West Eifel, Germany, suggests that the Coral Rapids rocks may be derived from magmas that originated from metasomatized mantle sources.

Enhanced and Rock Typing-Based Reservoir Characterization of the Palaeocene Harash Carbonate Reservoir-Zelten Field-Sirte Basin-Libya

2021 ◽  
Author(s):  
Mohamed Masoud ◽  
W. Scott Meddaugh ◽  
Masoud Eljaroshi ◽  
Khaled Elghanduri
Keyword(s):  
Rock Type ◽  
Carbonate Reservoir ◽  
Classification Model ◽  
Reservoir Rocks ◽  
The Core ◽  
Core Samples ◽  
Rock Types ◽  
Rock Typing ◽  
Open Hole ◽  
Type Classification

Abstract The Harash Formation was previously known as the Ruaga A and is considered to be one of the most productive reservoirs in the Zelten field in terms of reservoir quality, areal extent, and hydrocarbon quantity. To date, nearly 70 wells were drilled targeting the Harash reservoir. A few wells initially naturally produced but most had to be stimulated which reflected the field drilling and development plan. The Harash reservoir rock typing identification was essential in understanding the reservoir geology implementation of reservoir development drilling program, the construction of representative reservoir models, hydrocarbons volumetric calculations, and historical pressure-production matching in the flow modelling processes. The objectives of this study are to predict the permeability at un-cored wells and unsampled locations, to classify the reservoir rocks into main rock typing, and to build robust reservoir properties models in which static petrophysical properties and fluid properties are assigned for identified rock type and assessed the existed vertical and lateral heterogeneity within the Palaeocene Harash carbonate reservoir. Initially, an objective-based workflow was developed by generating a training dataset from open hole logs and core samples which were conventionally and specially analyzed of six wells. The developed dataset was used to predict permeability at cored wells through a K-mod model that applies Neural Network Analysis (NNA) and Declustring (DC) algorithms to generate representative permeability and electro-facies. Equal statistical weights were given to log responses without analytical supervision taking into account the significant log response variations. The core data was grouped on petrophysical basis to compute pore throat size aiming at deriving and enlarging the interpretation process from the core to log domain using Indexation and Probabilities of Self-Organized Maps (IPSOM) classification model to develop a reliable representation of rock type classification at the well scale. Permeability and rock typing derived from the open-hole logs and core samples analysis are the main K-mod and IPSOM classification model outputs. The results were propagated to more than 70 un-cored wells. Rock typing techniques were also conducted to classify the Harash reservoir rocks in a consistent manner. Depositional rock typing using a stratigraphic modified Lorenz plot and electro-facies suggest three different rock types that are probably linked to three flow zones. The defined rock types are dominated by specifc reservoir parameters. Electro-facies enables subdivision of the formation into petrophysical groups in which properties were assigned to and were characterized by dynamic behavior and the rock-fluid interaction. Capillary pressure and relative permeability data proved the complexity in rock capillarity. Subsequently, Swc is really rock typing dependent. The use of a consistent representative petrophysical rock type classification led to a significant improvement of geological and flow models.

scholarly journals Petrographic analysis of carbonate rocks for alkali-aggregate reactivity

1970 ◽  
Vol 14 ◽  
pp. 15-20
Author(s):  
Naresh Kazi Tamrakar ◽  
Lalu Prasad Paudel
Keyword(s):  
Rock Sample ◽  
Rock Type ◽  
Significant Proportion ◽  
Carbonaceous Material ◽  
Petrographic Analysis ◽  
Rock Types ◽  
Alkali Silica Reactivity ◽  
Alkali Carbonate ◽  
Alkali Aggregate Reactivity

Quality of aggregate is of extreme concern when it is to be used for infrastructures. Besides, many physical and mechanicalproperties of the aggregate, presence or absence of deleterious constituents and alkali-silica reactivity are especially importantwhen aggregates are to be used in concrete structures. High potential of alkali-silica reactivity or alkali-carbonate reactivity andpresence of deleterious constituents may impair the infrastructures.A ledge rock sample from the heap to be taken for crushing was petrographically analysed for alkali-silica reactivity. Inoverall, two rock clans (dolosparstone and dolomicrosparstone) with three sub clans (rock type X, Y and Z) from the sample 2 areidentified. Rock type X (dolosparstone) constitutes 82.94% of the whole sample, and shows notable amount of quartz and calciteveins, and carbonaceous material and hematite on the mosaic of dolospars. Rock types Y (dolosparstone) and Z (dolomicrosparstone)contain trace amount of microquartz, mega quartz (>15 mm) and carbonaceous opaques. The rock type Z is dominantly composedof dolomicrospars. Major portions of all the rock types are characterised by mosaics of dolomite in association with variableamounts of muscovite, quartz, and calcite. Calcite often replaces the mosaics of dolomite and bands of quartz, forming a veinnetworks in rock types X and Y. Silica is represented by a low-temperature mega quartz either in ground or in veins, a trace amountof microquartz in rock types Y and Z. There is no other reactive silica components, thus showing a low potential to alkali-silicareactivity. However, the sample shows potential of alkali-carbonate reactivity as significant proportion of rock type havingdolomicrospars are found.DOI: http://dx.doi.org/10.3126/bdg.v14i0.5433Bulletin of the Department of Geology Vol.14 2011, pp.15-20

scholarly journals Preparation of Thin Sections

1998 ◽  
Vol 6 (7) ◽  
pp. 8-9
Author(s):  
Ian Chaplin
Keyword(s):  
Chemical Composition ◽  
Thin Section ◽  
Microprobe Analysis ◽  
Rock Sample ◽  
Rock Type ◽  
X Rays ◽  
Thin Sections ◽  
Economical Method ◽  
Optical Examination ◽  
Composition Of Minerals

The optical examination of a rock sample in thin section is the quickest and most economical method for classifying rock type and determining which analytical route to follow.Thin sections for transmitted light are the most common, but there are also:Polished Thin Sections • Polished sections are used for classification and identification of minerals that cannot be determined in standard thin sections. They are also essential for microprobe analysis. Minute mineral grains are analyzed by bombarding them with a focused bean of electrons, which generate x-rays, characteristic of the elements within the grains. X-rays are identified and quantified to determine the chemical composition of minerals.

Metamorphic Rocks

2018 ◽  
Author(s):  
Alex Maltman
Keyword(s):  
Metamorphic Rock ◽  
Central Area ◽  
Tectonic Stress ◽  
Earth’S Crust ◽  
Metamorphic Rocks ◽  
Tectonic Plates ◽  
The Earth ◽  
Two Factors ◽  
Earth's Crust ◽  
Increased Pressure

We come now to the metamorphic rocks, the result of modifications to already existing rock. I’m well aware that this can all seem a bit mysterious. After all, no one has ever seen the changes take place; no one has ever witnessed a metamorphic rock form—the processes are imperceptibly slow, and they happen deep in the Earth’s crust, way out of sight. Why should these changes happen? Well, they are primarily driven by increases in pressure and temperature, so we begin with a look at these two factors. There are sites in the Earth’s crust where material becomes progressively buried. It happens, for example, where a tectonic plate is driving underneath another one, taking rocks ever deeper as it descends. It can happen in the central area of a plate that is stretching and sagging, allowing thick accumulations of sediment. It’s pretty self-evident that as buried material gets deeper, because of the growing weight of rocks above bearing down due to gravity, it becomes subjected to increasing burial pressure. Less intuitive, though, is the fact that this pressure acts on a volume of rock equally in all directions. Imagine a small volume of rock at depth. It’s bearing the weight of the rocks above it, and so it responds by trying to move downward and to spread out laterally. Of course, it can’t because it’s constrained all around by other volumes of rock that are trying to do exactly the same thing. And so the downward gravity is translated into an all-around pressure. It’s the same effect as diving down to the bottom of a swimming pool. You feel the increased pressure owing to the weight of water above, but you feel it equally in all directions. All-round pressure like this can cause things to change in volume, through changing their density, but it can’t change their shape. However, there can be another kind of pressure as well, and this does have direction, and it can cause change of shape. In the Earth, we call it tectonic stress. It comes about through heat-driven motions in the Earth, including the movement of tectonic plates.

scholarly journals Petrology of the metamorphic rocks (gravels) from Bhajanpur area in Panchagarh District, Bangladesh

1970 ◽  
Vol 5 ◽  
pp. 91-96
Author(s):  
Md Rahat Hossain ◽  
Ismail Hossain ◽  
ASM Zahid Hossain ◽  
Prodip Kumar Biswas
Keyword(s):  
Key Words ◽  
Metamorphic Rock ◽  
Metamorphic Rocks ◽  
Mica Schist ◽  
Mineral Assemblages ◽  
Temperature Ranges ◽  
Garnet Zone ◽  
Opaque Minerals ◽  
Mineralogical Compositions ◽  
Chlorite Schist

The present study deals with petrology of the detrital gravelly rocks from Bhajanpur area, Panchagarh, Bangladesh. The results of detailed petrography of gravelly rocks indicate the presence of quartz (monocrystalline and polycrystalline quartz), K-feldspar, plagioclase, chlorite, muscovite and biotite as major mineralogical compositions. Other minor minerals are garnet, kyanite, graphite and opaque minerals. Based on definitive mineral assemblages, blueschist and greenschist facies sequences are recognized. Correspondingly, index minerals provide chlorite zone, biotite zone, garnet zone, kyanite zone, and graphite zone. The P-T conditions of the studied rocks demonstrate the possible temperature ranges 300-550°C and pressure ranges 2-10 kbar. Most common varieties of metamorphic rocks in the study area are garnet mica schist, chlorite schist, gneiss and few quartzites. Characteristics of garnet mica schist and chlorite schist are equivalent with the lesser Himalayan metamorphic rock sequence in Sikkim area, whereas gneiss from Bhajanpur area has similar precursor as Darjeeling gneiss. Therefore, the sources of detrital metamorphic rocks in Bhajanpur area obviously come from the lesser Himalayan sequence in Sikkim and Darjeeling areas, India. Key words: Petrology; metamorphic rocks; gravels; P-T conditions; Panchagarh; lesser Himalayan sequence DOI: 10.3329/jles.v5i0.7357 J. Life Earth Sci., Vol. 5: 91-96, 2010

Liquid immiscibility and the origin of alkali-poor carbonatites

1988 ◽  
Vol 52 (364) ◽  
pp. 43-55 ◽  
Author(s):  
B. A. Kjarsgaard ◽  
D. L. Hamilton
Keyword(s):  
Liquid Immiscibility ◽  
Raw Material ◽  
Coarse Grained ◽  
Rock Types ◽  
Liquid Fractionation ◽  
Ring Complexes ◽  
The Common ◽  
Melt Cooling ◽  
Carbonate Melt ◽  
Common Sequence

AbstractThe work on liquid immiscibility in carbonate-silicate systems of Freestone and Hamilton (1980) has been extended to include alkali-poor and alkali-free compositions. Immiscibility is shown to occur on the joins albite-calcite and anorthite-calcite at 5 kbar. These results make it possible to interpret ocellar structure between calcite-rich spheroids in lamproite or kimberlite host rock as products of liquid immiscibility. The common sequence of rock types found in carbonatite complexes of melilitite-ijolite-urtite-phonolite is interpreted as being the result of both fractional crystallization and liquid fractionation, the corresponding carbonatite composition changing from nearly pure CaCO3 (±MgCO3) progressively to natrocarbonate. A carbonate melt cooling in isolation will suffer crystal fractionation, the residual liquid producing the rarer ferrocarbonatites, etc., whilst the crystal accumulate of calcite (dolomite) plus other phases such as magnetite, apatite, baryte, pyrochlore, etc., are the raw material for the coarse-grained intrusive carbonatites commonly found in ring complexes.

Comparative analysis of cyanobacteria inhabiting rocks with different light transmittance in the Mojave Desert: a Mars terrestrial analogue

2014 ◽  
Vol 13 (3) ◽  
pp. 271-277 ◽  
Author(s):  
Heather D. Smith ◽  
Mickael Baqué ◽  
Andrew G. Duncan ◽  
Christopher R. Lloyd ◽  
Christopher P. McKay ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Mojave Desert ◽  
Laser Scanning ◽  
Rock Type ◽  
Red Shift ◽  
Laser Scanning Microscopy ◽  
Light Transmittance ◽  
Confocal Laser ◽  
Rrna Gene ◽  
Rock Types

AbstractThe Mojave Desert has been long considered a suitable terrestrial analogue to Mars in many geological and astrobiological aspects. The Silver Lake region in the Mojave Desert hosts several different rock types (talc, marble, quartz, white carbonate and red-coated carbonate) colonized by hypoliths within a few kilometres. This provides an opportunity to investigate the effect of rock type on hypolithic colonization in a given environment. Transmission measurements from 300 to 800 nm showed that the transmission of blue and UVA varied between rock types. The wavelength at which the transmission fell to 1% of the transmission at 600 nm was 475 nm for white carbonate and quartz, 425 nm for red-coated carbonate and talc and 380 nm for marble. The comparative analysis of the cyanobacterial component of hypoliths under different rocks, as revealed by sequencing 16S rRNA gene clone libraries, showed no significant variation with rock type; hypoliths were dominated by phylotypes of the genusChroococcidiopsis, although less abundant phylotypes of the genusLoriellopsis, LeptolyngbyaandScytonemaoccurred. The comparison of the confocal laser scanning microscopy-λ (CLSM-λ) scan analysis of the spectral emission of the photosynthetic pigments ofChroococcidiopsisin different rocks with the spectrum of isolatedChroococcidiopsissp. 029, revealed a 10 nm red shift in the emission fingerprinting for quartz and carbonate and a 5 nm red shift for talc samples. This result reflects the versatility ofChroococcidiopsisin inhabiting dry niches with different light availability for photosynthesis.

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