scholarly journals PALEOGENIC BASALT-TRACHYTIC FORMATION OF WEST CAUCASUS: GEOCHEMICAL SPECIALIZATION, QUESTION OF PETROGENESIS, GEODYNAMIC TYPISATION, METALLOGENY

2018 ◽  
Author(s):  
В.М. Газеев ◽  
А.Г. Гурбанов ◽  
И.А. Кондрашов
Keyword(s):  
Upper Mantle ◽  
Rare Metal ◽  
Spinel Peridotite ◽  
Western Margin ◽  
Tectonic Processes ◽  
Icp Ms ◽  
Scythian Plate ◽  
Geochemical Investigation ◽  
Sea Area ◽  
Geochemical Specialization

В юго-западной части Большого Кавказа в среднем течении р. Мзымты встречаются палеогеновые субщелочные породы основного и среднего составов. Проведено петрографическое и геохимическое изучение пород и приведены результаты их анализов методами RFA, ICP-MS. Установлено обогащение пород LILe, REE, HFSE, концентрации которых сопоставимы с OIB. Выявлена геохимическая редкометалльно–редкоземельная специализация пород БТФ, а их металлогеническая специализация – ртутная и титановая. Показано, что исходные расплавы возникли при 2-3% плавлении шпинелевого перидотита. Предполагается, что причиной появления частичных выплавок в верхней мантии являлись тектонические процессы, затронувшие территорию юго-западной окраины Скифской плиты, и синхронные с процессами рифтообразования, развивавшимися в эоцене в Черноморском регионе и Аджаро-Триалетском прогибе. In the south-western parts of Geater Caucasus in the middle cource of river Mzimta the Paleogenic subalkaline rocks of basic and medial composition are occur. Petrographical and geochemical investigation have been carrying out and results of its analysis by RFA, ICP-MS methods was done. Enrichment of rocks by LILe, REE, HFSE, concentration of which are comparison with OIB have been identify. Rare-metal and rare-earth geochemical specialization of BTF rock is identified and its mercury and titanium metallogenic specialization. It is shown, that primary melts are appears in 2-3% melting of spinel peridotite. It is suggested that the reason of initiation of the partial melting in the upper mantle was a tectonic processes, which are touched on area of south-western margin of Scythian plate, synchronous with processes of rifting which are developing in Eocene in Black Sea area and in Adjaro-Trialeti depression

scholarly journals Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Costanza Bonadiman ◽  
Valentina Brombin ◽  
Giovanni B. Andreozzi ◽  
Piera Benna ◽  
Massimo Coltorti ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Simultaneous Formation ◽  
Empirical Potentials ◽  
Elastic Data ◽  
Mineralogical Study ◽  
Semi Empirical ◽  
T Locus

AbstractThe occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P–T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3–3.0 GPa/540–1500 K, yields a negative Clapeyron slope of -0.003 GPa K–1 (on average). The intersection of the P–T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = –1.97 ± 0.35; –1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

scholarly journals Water contents of nominally anhydrous orthopyroxenes from oceanic peridotites determined by SIMS and FTIR

2021 ◽  
Author(s):  
Kirsten T. Wenzel ◽  
Michael Wiedenbeck ◽  
Jürgen Gose ◽  
Alexander Rocholl ◽  
Esther Schmädicke
Keyword(s):  
Upper Mantle ◽  
Secondary Ion Mass Spectrometry ◽  
Spinel Peridotite ◽  
Structural Water ◽  
Major Element Composition ◽  
Mantle Peridotites ◽  
History Of ◽  
Polarized Ftir ◽  
Water Contents ◽  
Forearc Region

AbstractThis study presents new secondary ion mass spectrometry (SIMS) reference materials (RMs) for measuring water contents in nominally anhydrous orthopyroxenes from upper mantle peridotites. The enstatitic reference orthopyroxenes from spinel peridotite xenoliths have Mg#s between 0.83 and 0.86, Al2O3 ranges between 4.02 and 5.56 wt%, and Cr2O3 ranges between 0.21 and 0.69 wt%. Based on Fourier-transform infrared spectroscopy (FTIR) characterizations, the water contents of the eleven reference orthopyroxenes vary from dry to 249 ± 6 µg/g H2O. Using these reference grains, a set of orthopyroxene samples obtained from variably altered abyssal spinel peridotites from the Atlantic and Arctic Ridges as well as from the Izu-Bonin-Mariana forearc region was analyzed by SIMS and FTIR regarding their incorporation of water. The major element composition of the sample orthopyroxenes is typical of spinel peridotites from the upper mantle, characterized by Mg#s between 0.90 and 0.92, Al2O3 between 1.66 and 5.34 wt%, and Cr2O3 between 0.62 and 0.96 wt%. Water contents as measured by SIMS range from 68 ± 7 to 261 ± 11 µg/g H2O and correlate well with Al2O3 contents (r = 0.80) and Cr#s (r. = -0.89). We also describe in detail an optimized strategy, employing both SIMS and FTIR, for quantifying structural water in highly altered samples such as abyssal peridotite. This approach first analyzes individual oriented grains by polarized FTIR, which provides an overview of alteration. Subsequently, the same grain along with others of the same sample is measured using SIMS, thereby gaining information about homogeneity at the hand sample scale, which is key for understanding the geological history of these rocks.

Lithogeochemical characteristics of metasandstones of the Chetlas series (Chetlassky Kamen, Middle Timan)

2021 ◽  
pp. 3-12
Author(s):  
N. Y. Nikulova ◽  
◽  
O. V. Udoratina ◽  
I. V. Kozyreva
Keyword(s):  
Inductively Coupled Plasma ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Weathering Crust ◽  
Terrigenous Material ◽  
Inductively Coupled ◽  
Coastal Marine ◽  
Icp Ms ◽  
Middle Timan ◽  
Destruction Of Rocks

The lithological and geochemical features of the metasandstones of the Svetlinskaya and Vizingskaya formations of the Middle Late Riphean Chetlas series in the Middle Timan, which are a substrate of rare-metal-rare-earth mineralization in several ore occurrences of the Kosyus ore cluster, have been investigated. The interpretation of the results of traditional weight chemical and mass spectrometric inductively coupled plasma (ICP MS) analyses allowed us to identify differences in the material composition of metapesanics, mainly due to changes in the degree of sedimentation maturity of terrigenous material coming from the demolition areas. The composition of metasandstones in various ratios includes both weakly weathered products of destruction of volcanic rocks of intermediate/basic composition, and altered, including under conditions of the weathering crust, metaterrigenous formations. The accumulation of sediments took place in a shallow coastal-marine environment with changing hydrodynamics, which affected the rate of destruction of rocks in paleo-catchments.

Geochemistry of spinel peridotite inclusions in basalts from Sardinia

1987 ◽  
Vol 51 (362) ◽  
pp. 561-568 ◽  
Author(s):  
C. Dupuy ◽  
J. Dostal ◽  
J. L. Bodinier
Keyword(s):  
Upper Mantle ◽  
Mineral Assemblage ◽  
Spinel Peridotite ◽  
Primary Mineral ◽  
Compositional Variations

AbstractThe spinel peridotite inclusions in basalts from Sardinia are upper-mantle residues affected by metasomatism which led to an enrichment particularly of U and light REE. The metasomatism took place prior to the recrystallization which produced the primary mineral assemblage of the inclusions. The compositional variations imply that the xenoliths are residual after at least two melting events.

scholarly journals Structure and age of the fluorite-berillium deposit of the field Rainbow, Western Sayan Mountains: to the problem of assessment of metallogenic prospects of the territory

2019 ◽  
Vol 488 (3) ◽  
pp. 282-287
Author(s):  
D. A. Lykhin ◽  
V. V. Yarmolyuk ◽  
A. A. Vorontsov ◽  
A. V. Travin
Keyword(s):  
Carbonate Rocks ◽  
Rare Metal ◽  
Early Paleozoic ◽  
Geochemical Parameters ◽  
Rare Metal Mineralization ◽  
Metallogenic Zone ◽  
Western Sayan ◽  
The Relationship ◽  
Good Agreement ◽  
Geochemical Specialization

The age and geochemical parameters of the muscovite-fluorite-euclase-beryl Raduga deposit, which is located within the Kizir-Kazyr zone of rare-metal magmatism, are determined. In contrast to other deposits and ore occurrences of the zone, represented by alkaline granites characterized by rare metal mineralization, the Raduga deposit is associated with metasomatites in carbonate rocks. The age of the deposit, estimated at 40Ar/39Ar by the muscovite method of beryllium fluorite-muscovite greisens, is 469.3± 4.5Ma. It corresponds to the age of the ore-bearing alkaline granites of the zone. The dikes which occur within the deposit are identical by the composition to the dikes of rare-metal alkaline granitic massifs, one of which is located in a few kilometers from the deposit. The nature of the ore Be-Li mineralization of the deposit is in good agreement with the geochemical specialization of the Early Paleozoic Kizir-Kazyr metallogenic zone. The revealed features of the relationship between Raduga deposit and rare-metal deposits in alkaline granites suggests a variety of mechanisms involved in the formation of rare-metal deposits of the Kizir-Kazyr zone. Thus, it allows to expand approaches for prediction and exploration of rare-metal deposits in the region.

scholarly journals APATITE-ALBITE METASOMATITES (ACEITES) OF THE EASTERN ALDAN-STANOVOY SHIELD

2021 ◽  
Vol 40 (5) ◽  
pp. 59-73
Author(s):  
V.E. Kirillov ◽  
Keyword(s):  
Rare Earth ◽  
Structural Control ◽  
Earth Element ◽  
Rare Metal ◽  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Intrusive Rocks ◽  
Characteristic Features ◽  
Metasomatic Zoning ◽  
Geochemical Specialization

The paper summarizes the findings of research on Riphean ore-bearing apatite-albite metasomatites (aceites) identified in metamorphic, volcanic and intrusive rocks in the eastern Aldan-Stanovoy shield. The characteristic features of lithological and structural control of aceites, their mineral and petrochemical composition, geochemical associations, ontogeny, metasomatic zoning, and geochemical specialization are outlined. Aceites in metamorphic rocks are assigned to the albite-chlorite-apatite facies and in igneous rocks to the albite-apatite facies. Apatite-albite metasomatites host mineralization of two types: uranium (in aceites after metamorphic rocks) and uranium – rare earth element – rare metal (in aceites after volcanic and intrusive rocks).

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