scholarly journals Petrogenesis and Geochemical Properties of Dome-shaped Subvolcanic Complexes in Southwest of Shahrab (Northeast of Isfahan)

2017 ◽  
Vol 7 (4) ◽  
pp. 316-324
Author(s):  
Mohammad Ali Arian ◽  
Alikhan Nasr Isfahani ◽  
Afsaneh Ranjbar
Keyword(s):  
Alkali Feldspar ◽  
High Potassium ◽  
Ornamental Stone ◽  
Continental Plate ◽  
Geochemical Properties ◽  
Eu Anomaly ◽  
Tectonic Environment ◽  
High Enrichment ◽  
Opaque Minerals ◽  
Primary Magmas

<p>The studied area is located in southwest of Shahrab village near Ardestan city. This zone is part of Uremia- Dokhtar magmatic belt. Outcrops composed of rhyolite and rhyodacite dome-shaped volcanic complexes are scattered in the studied area; some of which are exploited as ornamental stone. The main rhyolite minerals include quartz, plagioclase and alkali feldspar. Minor minerals include Apatite, Sphene and opaque minerals and of the secondary minerals in these rocks Christie, Chlorite, Epidote and calcite could be mentioned. Calcite exists in rocks in form of filler of micro-fissures. The ignimbrite presence in this group of rocks in form of xenolith is one of the features of this rock group. The main primary texture in rhyolite and rhyodacite is porphyritic and the secondary texture includes pull-apart, snow flake and spherulitic textures. Geochemical evidences indicate that these rocks are sub-alkaline, Calc-alkaline compositions with high potassium and meta-alumina. These rocks have negative EU anomaly that is the feature of acidic igneous rocks. The studied rocks show high enrichment of LREE and LILE elements. The primary magmas constituting these rocks have mantel origin raised under extreme compressional conditions on continental crust in a tectonic environment of volcanic arc. It seems that these rocks are formed in connection with continuance of volcanic activities associated with subduction of Neolithic oceanic plate beneath continental plate of Iran. </p>

scholarly journals THE A-TYPE KERKINI GRANITIC COMPLEX IN NORTH GREECE: GEOCHRONOLOGY AND GEODYNAMIC IMPLICATIONS

2007 ◽  
Vol 40 (2) ◽  
pp. 700 ◽  
Author(s):  
G. Christofides ◽  
A. Koroneos ◽  
Α. Liati ◽  
J. Kral
Keyword(s):  
Genetic Model ◽  
Rock Type ◽  
White Mica ◽  
Metamorphic Fluid ◽  
Initial Ratio ◽  
Crustal Source ◽  
Eu Anomaly ◽  
Tectonic Environment ◽  
Fluid Event

The Kerkini granitic complex (KGC) intrudes the Serbomacedonian massif KGC comprises the Mûries granite (MUR), the Miriofito granite (MIR), and the Kastanusa (KAS) granodiorite. The main rock-type is two-mica granite. Feldspars are represented by albite andperthitic microcline, biotite is iron-rich and white mica is phengite. Fluorite is also present. The rocks are peraluminous, enriched in total alkalis, depleted in MgO and CaO and have high FeOt/MgO ratios. They are enriched in Zr, Nb, Y, Ga and REE, and have strong negative Eu anomaly. They plot in the Atype granite fields of various discriminant diagrams and their chemistry suggests a WPG tectonic environment. Sr initial ratio ranges from 0.7107 to 0.7182. The most probable genetic model is fluid-absent melting of a biotite-rich tonalitic crustal source at 950 -975 C and at considerable depths. Rb-Sr white mica ages and SHRIMP U-Pb zircon ages yielded 246±3 Ma and 247±2Ma, respectively, interpreted as the crystallization age of the KGC. K-Ar ages of 130±3 and 131 ±3 Ma (biotite) and 133±3 Ma (white mica) can be interpreted by a metamorphic/fluid event at about 133 Ma. Rb-Sr white mica dates at 152±2 Ma probably resulted by incomplete resetting of the Rb-Sr isotopie system and yielded "mixing ages" between crystallization (ca. 247 Ma) possibly related to a Permian - Triassic rift event and metamorphic/fluid event (ca. 133 Ma).

scholarly journals Dust Characterization and Its Potential Impact during the 2014–15 Fogo Volcano Eruption (Cape Verde)

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1275
Author(s):  
Carla Candeias ◽  
Paula F Ávila ◽  
Célia Alves ◽  
Carla Gama ◽  
Cristina Sequeira ◽  
...  
Keyword(s):  
Air Quality ◽  
Size Fraction ◽  
Chemical Characterization ◽  
Contamination Factor ◽  
Active Volcano ◽  
Cape Verde ◽  
Atmospheric Particulate Matter ◽  
Saharan Dust ◽  
High Potassium ◽  
High Enrichment

Fogo (Fogo Island) is the youngest and most active volcano of Cape Verde. The last eruption occurred in 2014–2015. Aiming to assess the dust sources that impacted the air quality during the present study period, fresh lava samples were collected, while Saharan dust intrusions and transport were modeled. Rooftop dust was also collected on the island dwellings and a mineralogical and chemical characterization was undertaken. Air quality monitors were used to obtain concentrations of atmospheric particulate matter (PM) and gaseous pollutants. The mineralogical constitution was assessed by XRD and Electron Microprobe. The pseudototal chemical concentration was performed by XRF, ICP-MS and SEM; the latter includes particles morphology. During the study, WRF-CHIMERE results showed the intrusion of desert dust which affected the air quality. Lava was classified as tephritic to basanitic, with high potassium content. The Pollution Load Index for rooftop dust was >1 in all samples, suggesting an enrichment. Higher values were found in dust size fraction <63 µm, with contamination factor pointing to high enrichment of As, Ni and Pb, and very high enrichment of Cd. The non-carcinogenic hazard estimated for children suggested that health problems may arise. The carcinogenic risk was above the target risk, mostly due to As > Pb > Co. Ingestion was the main exposure route. PM10 concentrations exceeded the 24-hour mean of 50 µg/m3 recommended by WHO. Nevertheless, TVOCs displayed levels lower than guidelines. The highest levels of CO2 were recorded in more populated villages and farthest from the volcano.

Eclogite and garnet pyroxenite xenoliths from kimberlite pipes of north Siberian craton - evidences of subduction processes and cumulate origin

2021 ◽  
Author(s):  
Tatiana Kalashnikova ◽  
Lidia Solov'eva ◽  
Sergey Kostrovitsky ◽  
Konstantin Sinitsyn ◽  
Elvira Yudintseva
Keyword(s):  
Mineral Composition ◽  
Siberian Craton ◽  
Lithospheric Mantle ◽  
Isotope Composition ◽  
Bulk Composition ◽  
Mantle Xenoliths ◽  
Rock Composition ◽  
Geochemical Properties ◽  
Eu Anomaly ◽  
Wide Range

&lt;p&gt;The lithospheric mantle structure and evolution is one of the fundamental problems of the Earth's history. Eclogites and clinopyroxenite xenoliths are characterized by a similar two-mineral composition (garnet and clinopyroxene), but differ in mineralogical and petrographic features (Gonzaga et al., 2010). Questions of their origin and relationship with peridotites remain controversial. There are several classifications of eclogites based on various attributes: structural and textural features (Mercier &amp; Nicolas, 1975; MacGregor &amp; Carter, 1970), chemical composition of garnet (Coleman, 1965), clinopyroxene (Taylor &amp; Neal, 1989), as well as the whole rock composition (Aulbach et al., 2016 and other), the given classifications may not coincide. The geochemical properties of eclogite xenoliths from kimberlite pipes suggest two main points of view for genesis: implication of subduction processes or cumulates of high-pressure melting in lithosphere mantle (Condie, 1993; Jacob et al., 1994). The &quot;classical&quot; cratonic eclogites represent an ancient oceanic crust subsequently subducted and altered possible further metasomatic processes. These rocks are characterized by significant variations in the composition of minerals, a relatively high content of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (14-20 wt%) and a low MgO content (10-15 wt%), depletion of elements of the LREE and an Eu anomaly (Gonzaga et al., 2010). In addition, eclogites have a wide range of oxygen isotopic composition in garnet &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O 4.51 - 8.69 (much higher than mantle values &amp;#8203;&amp;#8203;5.3 &amp;#177; 0.3) (9). Garnet pyroxenites are characterized by a more magnesian garnet - pyrope and bulk composition (MgO - 15-20 wt.%). The oxygen isotope composition of Grt from clinopyroxenites is close to that of the mantle - &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O 5.2 - 5.8. It is assumed that these rocks are a consequence of the polybaric partial melting at high temperatures and pressures (Gonzaga et al., 2010). The mantle xenoliths from upper-Jurassic Obnajennaya kimberlite pipe (Kuoika field, Yakutia) were studied. Eclogites and clinopyroxenites occupy about 10-15% population among xenoliths. Garnet in the eclogites differs from that in the clinopyroxenites by a higher content of CaO and FeO (Prp&lt;sub&gt;55-62 &lt;/sub&gt;Alm&lt;sub&gt;22-30&lt;/sub&gt;Grs&lt;sub&gt;8-18 &lt;/sub&gt;in clinopyroxenites and Prp&lt;sub&gt;40-45&lt;/sub&gt;Alm&lt;sub&gt;13-29&lt;/sub&gt;Grs&lt;sub&gt;15-30 &lt;/sub&gt;in eclogites). Clinopyroxenes are distinguished by reduced magnesia content (Mg# 91-84), as well as low calcium content (16-18 wt.%). The high contents of jadeite components in the clinopyroxene (NaAl[Si&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;] - 25-32%) classify this group of rocks as eclogites. The high &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O varies in eclogite Cpx (more than 6.0), positive Eu anomaly is assumed that the formation of the protolith of the xenolith group occurred as melts in the subduction zone during accretion of the Birekte block to the Siberian craton (Rosen, 2003). However, the presence of garnet clinopyroxenites with narrow variations in mineral composition and relatively low &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O suggests melting processes in the lithospheric mantle and the formation of megacrystalline pyroxene cumulates.&lt;/p&gt;&lt;p&gt;The research was supported by Russian Science Foundation grant &amp;#8470;20-77-00074.&lt;/p&gt;

scholarly journals Petrological and Geochemical Properties of Greek Carbonate Stones, Associated with Their Physico-Mechanical and Aesthetic Characteristics

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 507
Author(s):  
Ioanna Badouna ◽  
Petros Koutsovitis ◽  
Christos Karkalis ◽  
Konstantinos Laskaridis ◽  
Nikolaos Koukouzas ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Structural Defects ◽  
Ornamental Stone ◽  
Geochemical Properties ◽  
Hydrothermal Processes ◽  
Ornamental Stones ◽  
Wide Range ◽  
Chemical Constitution ◽  
Aesthetic Characteristics ◽  
And Chemical Properties

Greece is considered amongst the world’s top marble producers in the global carbonate ornamental stone market. Selected Greek carbonate ornamental stones considered in our study suite are characterized by their distinctive and in some cases unique appearance, having a significant impact on their commercial value. Their wide range of colour varieties and their physico-mechanical properties are closely related to their mineral assemblage, chemical constitution, petrographic properties, structural defects, which in turn depend highly upon their metamorphic/diagenetic grade and in some cases hydrothermal processes that affected them. This study endeavors to feature the petrographic, mineralogical and geochemical properties of the main Greek carbonate ornamental stones from selected localities and their by-product waste material used as aggregates. The documented data aims to serve a better understanding of the dynamic Greek marble industry by relating their mineral and chemical properties with their physico-mechanical and aesthetic characteristics.

Lower crustal granulite xenoliths in carbonatite volcanoes of the Western Rift of East Africa

1987 ◽  
Vol 51 (363) ◽  
pp. 621-633 ◽  
Author(s):  
C. W. Thomas ◽  
P. H. Nixon
Keyword(s):  
East Africa ◽  
Alkali Feldspar ◽  
Fractional Crystallisation ◽  
Metamorphic Grade ◽  
Eu Anomaly ◽  
South West ◽  
Garnet Granulite ◽  
Lower Crustal ◽  
Basaltic Melts ◽  
Granulite Xenoliths

AbstractSporadic small garnet granulite and two-pyroxene granulite xenoliths found in the carbonatite tuffs and lavas near Fort Portal, South West Uganda, are chiefly silica-saturated and rich in Al2O3 (> 20 wt. %) and Na2O (c. 2 to 4 wt. %). Three REE patterns are distinguished: LREE enriched—HREE depleted with a positive Eu anomaly; LREE depleted—HREE relatively enriched and flat; and LREE slightly enriched with a very weak Eu anomaly and high overall REE. The xenoliths are considered to represent original basaltic melts and fractional crystallisation products, varying with the dominance of the clinopyroxene, plagioclase or olivine crystallising phase. It is thought that REE abundances were established before metamorphism.The clinopyroxenes are low-jadeitic augites, the orthopyroxenes, aluminous hypersthenes and the garnets, pyrope-almandine with constant grossularite. Plagioclase varies with increasing metamorphic grade from labradorite to andesine-oligoclase. Scapolite (meionite), alkali-feldspar, quartz, mica, amphibole, rutile and apatite are minor phases and some appear to be metasomatic.Calculated temperatures of metamorphic equilibration range from 580 to 800°C at pressures > 4 kbar for the two-pyroxene granulites and > 6 kbar for the garnet granulites. A known geophysical discontinuity marking a density change at 16 km in the Western Rift may be due to the presence of two-pyroxene granulite, calculated to become garnet-bearing at depths greater than 23 km. The absence of proven omphacite-bearing eclogite xenoliths (with no plagioclase) indicates that the greatest depth of crustal sampling by the carbonatite in the Fort Portal field is about 25 km which could be the depth of the Moho in this area.

Geochemistry Characteristics of Cenozioc Alkaline-Rich Intrusions and its Forming Tectonic Setting in Jiudingshan Porphyry Cu-Mo Polymetallic Deposit, West Yunnan

2013 ◽  
Vol 868 ◽  
pp. 125-128
Author(s):  
Yan Dao ◽  
Feng Li ◽  
Wang Rong
Keyword(s):  
Tectonic Setting ◽  
High Alumina ◽  
High Potassium ◽  
Porphyry Cu ◽  
Polymetallic Deposit ◽  
Eu Anomaly ◽  
High K ◽  
Lree Enrichment ◽  
Granite Type ◽  
Geochemistry Characteristics

Geochemistry Characteristics of iudingshan Porphyry Cu-Mo Polymetallic Deposit are analyzed in the presented work. The Jiudingshan alkaline-rich porphyry is formed in Cenozoic (from 52 Ma to 29 Ma), being characterized by high potassium, rich alkali and high alumina can be attributed to high K calc alkaline series and shoshonite series, which showing LREE enrichment, HREE depletion, weak negative Eu anomaly (δEu=0.72~1.02, av.=0.86) close to the crust-mantle granite type (δEu=0.83) and mainly is formed in a post-collisional intraplate tectonic setting.

scholarly journals Petrography of Allanite-bearing Tonalite from Iwo Region, Osun State, Nigeria

2020 ◽  
Vol 67 (2) ◽  
pp. 79-89
Author(s):  
E.J. Oziegbe ◽  
O.O. Ocan ◽  
A.O. Buraimoh
Keyword(s):  
Alkali Feldspar ◽  
Precambrian Basement ◽  
Basement Complex ◽  
Southwestern Nigeria ◽  
Compositional Zoning ◽  
Thin Sections ◽  
Accessory Minerals ◽  
Secondary Minerals ◽  
Mineral Assemblages ◽  
Opaque Minerals

AbstractPrimary, secondary and accessory minerals in tonalitic rocks from Iwo region of the Precambrian Basement Complex of Southwestern Nigeria were identified and analysed with the aim of determining the various processes involved during the crystallisation of magma. Thin sections of tonalite were prepared and studied with the aid of a petrographic microscope. The mineral assemblages observed are biotite, plagioclase, alkali-feldspar, amphiboles, pyroxene, quartz, muscovite and chlorite. Allanite, titanite, apatite and zircon occur as accessory minerals. Muscovite and chlorite are found to be secondary minerals. The mineral allanite has a characteristic form of zoning and shows evidence of metamictisation, and is surrounded by dark-coloured biotite having radioactive haloes. Titanite is anhedral to subhedral crystals and forms reaction rim round opaque minerals. Plagioclase shows evidence of compositional zoning as well as plastic deformation of the twin lamellae. The allanite observed is primary in nature and has undergone radioactive disintegration; chlorite and muscovite are formed by secondary processes of chloritization and sericitisation, respectively. The tonalite is formed as a result of rapid cooling of magma close to the Earth's surface.

The Highwood Mountains potassic igneous province, Montana: mineral fractionation trends and magmatic processes revisited

2012 ◽  
Vol 76 (4) ◽  
pp. 1005-1051 ◽  
Author(s):  
C. M. B. Henderson ◽  
F. R. Richardson ◽  
J. M. Charnock
Keyword(s):  
Major Element ◽  
Magma Mixing ◽  
Alkali Feldspar ◽  
Bulk Rock ◽  
Magma Chambers ◽  
Igneous Province ◽  
Rock Analysis ◽  
Volatile Loss ◽  
Primary Magmas ◽  
Alkali Feldspars

AbstractPotassium-rich mafic dykes and lavas from the Highwood Mountains Igneous Province, USA were studied by electron-microprobe and bulk-rock analysis. For the mafic phonolites, compositional trends for olivine and augite phenocrysts and groundmass biotite, alkali feldspar and titanomagnetites are presented and substitution mechanisms discussed. Phenocrysts of biotite and augite in the minettes are also characterized, together with groundmass alkali feldspar and titanomagnetite. The alkali feldspars and biotites are commonly enriched in Ba. Olivine, clinopyroxene and biotite phenocrysts are generally quite magnesium-rich, which is consistent with the primitive natures of the least evolved rocks.Bulk-rock major-element compositions are combined with modal and microprobe data for the principal phenocrysts to calculate model residual liquid compositions for mafic phonolites, minettes and a syenitic rock. On the basis of phase-equilibria, it is suggested that the main controls of differentiation are polybaric involving crystallization during transport of primary magmas from the mantle for the minettes, and low-pressure differentiation for the mafic phonolites. Whereas magma mixing might have contributed to petrogenesis, many of the disequilibrium features exhibited by clinopyroxene and biotite phenocrysts can also be attributed to pre-existing phenocrysts undergoing decompression melting during magma uprise from its mantle source, followed by rapid crystal growth and episodic volatile loss in sub-volcanic magma chambers.

scholarly journals Geotermobarometria y Quimica Mineral del Pluton Sienito "Pajeú" Serra Talhada, Pernambuco, NE de Brasil

1998 ◽  
Vol 25 (1) ◽  
pp. 61
Author(s):  
CRISTINA NANCY REYES
Keyword(s):  
Alkali Feldspar ◽  
Mineral Chemistry ◽  
Northeastern Brazil ◽  
Calc Alkaline ◽  
Calcic Plagioclase ◽  
Perfect Agreement ◽  
Fine Grained ◽  
Microgranular Enclaves ◽  
High Alkali ◽  
Opaque Minerals

The Pajeu Syenitic Complex, Serra Talhada, Pernambuco province, northeastern Brazil is tectonically emplaced within the framework of Neoproterozoic (Brasiliano). In the present work were studied whole rock and specific mineral chemical data (85’24” – 816’31” S and 3819’8” – 3836’2” W). Two distinct petrographic facies have been identified. The predominant porphyritic syenite facies is characterized by perthite microcline megacrysts (up to 8 cm long) and fine grained syenite; both facies have distributed melanocratic microgranular enclaves of syenitic composition. The mineral assemblage comprising alkali feldspar, plagioclase, quartz, biotite, hornblende and accessory amounts of zircon, opaque minerals, epidote, allanite, sphene etc. the geochemical signatures define overlapping calc-alkaline and shoshonitic affinities and metaluminous to peraluminous nature. The complex is characterized by silica enrichment (62.2% - 72.4%), moderate alumina (14% - 16.6%) and high alkali abundance (8.6% - 9.1%). The enclaves have low silica (54.2% - 56.4%) and corresponding enrichment in mafic phases. High alkali abundance, preponderance of K2O over Na2O and TiO2 variation between 0.22% to 0.57% are in agreement with shoshonitic affinities. Mineral chemistry of amphiboles enables their classification as edenite – magnesian hornblende. The micas are mainly magnesian biotite. Plagioclase is usually oligoclase (An20) and K-feldspar is orthoclase. The geochemical signatures of biotite and amphibole are in perfect agreement with the other shoshonitic rocks of northeastern of Brazil. Temperatures estimateds for calcic plagioclase and amphibole pairs indicate a temperature range of 646-671C for porphyritic syenite and 629-650C for enclaves. Geobarometric estimates, using Al in amphiboles indicate equation pressure of 1,48 Kbar to 2,26 Kbar for porphyritic syenite and 1,01 Kbar for enclaves. Other pressure estimates yielding 2,25 Kbar to 2,91 Kbar and 1,76 Kbar respectively, though at variance with the earlier estimates correspond with epizonal emplacement of the pluton.

scholarly journals Petrography, geochemistry and Sm-Nd isotopes of the granites from eastern of the Tapajós Domain, Pará state

2016 ◽  
Vol 46 (4) ◽  
pp. 509-529 ◽  
Author(s):  
Flávio Robson Dias Semblano ◽  
◽  
Moacir José Buenano Macambira ◽  
Marcelo Lacerda Vasquez ◽  
◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Alkali Feldspar ◽  
Eu Anomaly ◽  
High K ◽  
Amazonian Craton ◽  
Heavy Rare Earth Elements ◽  
Type Granite ◽  
Archean Crust ◽  
Intrusive Suite

ABSTRACT: The Tapajós Domain, located in the southern portion of the Amazonian Craton, is a tectonic domain of the Tapajós-Parima Province, a Paleoproterozoic orogenic belt adjacent to a reworked Archean crust, the Central Amazonian Province. This domain has been interpreted as the product of an assemblage of successive magmatic arcs followed by post-orogenic A-type magmatism formed ca. 1880 Ma-old granites of the Maloquinha Intrusive Suite. The study presented here was carried out in four granitic bodies of this suite (Igarapé Tabuleiro, Dalpaiz, Mamoal and Serra Alta) from the eastern part of the Tapajós Domain, as well as an I-type granite (Igarapé Salustiano) related to the Parauari Intrusive Suite. The A-type granites are syenogranites and monzogranites, and alkali feldspar granites and quartz syenites occur subordinately. These rocks are ferroan, alkalic-calcic to alkalic and dominantly peraluminous, with negative anomalies of Ba, Sr, P and Ti and high rare earth elements (REE) contents with pronounced negative Eu anomaly. This set of features is typical of A-type granites. The Igarapé Salustiano granite encompasses monzogranites and quartz monzonites, which are magnesian, calcic to calc-alkalic, high-K and mainly metaluminous, with high Ba and Sr contents and depleted pattern in high field strength elements (HFSE) and heavy rare earth elements (HREE), characteristic of I-type granites. The source of magma of these A-type granites is similar to post-collisional granites, while the I-type granite keeps syn-collisional signature. Most of the studied granites have εNd (-3.85 to -0.76) and Nd TDM model ages (2.22 to 2.46 Ga) compatible with the Paleoproterozoic crust of the Tapajós Domain. We conclude that the Archean crust source (εNd of -5.01 and Nd TDM of 2.6 Ga) was local for these A-type granites.

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