Showing 5 results for Enrichment
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Volume 15, Issue 1 (4-2007)
Abstract
Mafic rocks including basalts and gabbros are the main constituents of Birjand ophiolites. They are found in several places and show low grade metamorphism in the field and under the microscope. Chondrite-normalized REE patterns for basalts and gabbros indicate that these rocks are transitional-enriched to depleted mid-oceanic ridge basalts respectively. Otherwise, N-MORB normalized trace elements patterns for basalts and gabbros are considered to be enriched in some LIL elements. Depletion in Ti and also in Nb (in gabbros) is other characteristic of these rocks. Therefore an incomplete short-lived subduction regime for generation of those heterogeneities can be suggested. The primary mantle-normalized trace elements pattern for Birjand harzburgite also confirms some LIL enrichments.
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Volume 24, Issue 4 (1-2017)
Abstract
In north to northeast of Baft city, south Kerman, various outcrops of volcanic rocks, belong to Uromieh-Dokhtar magmatic belt, are observed. This region in Kerman Province situated in east of Dehaj – Sarduiye magmatic belt. Most of volcanic sequences in this area are andesite, andesite-basalt, dacite, and a few basalt and rhyolite with Eocene age that interlayered with pyroclastic and volcano sedimentary rocks with ignimbrites lavas. Study of rocks in this area and vocinity rocks showed that calco-alkaline series is dominant for these rocks. Major minerals include plagioclase, hornblende, biotite and pyroxene. Plagioclase phenocrysts in these rocks are shown inequilibrium texture such as zoning and sieves texture. From important textures in these volcanic rocks are porphyry, hyaloporphyry, microlitic and flowing. According to obtained results from analysis, these rocks showed enrichment from LREEs than to HREE. Also higher values of LILE than HFSE and negative anomaly in Ti, Nb and P in lavas revealed a subduction zone tectonic setting for this region and showed that primary magma are formed from mantle wedge melting in contact with derived oceanic crust flowing and enriched from LREEs originated.
Maryam Kiaeshkevarian, Aliasghar Calagari, Ali Abedini, Gholamhosain Shamanian,
Volume 27, Issue 3 (10-2019)
Abstract
The Siahrudbar deposit is located about 25 km southwest of Aliabad-Katool city in the Golestan Province, north of Iran. This deposit lies between the Triassic limestone (Elika Formation) and Jurassic sandstone (Shemshak Formation). Mineralogical studies indicate the presence of major minerals such as diaspore, hematite, anatase, kaolinite, and chamosite accompanied by minor minerals such as boehmite, goethite, rutile, calcite, moscovite, clinoclar, quartz, and tridymite. Calculation of enrichment factor showed that the bauxitization processes at Siahrudbar were accompanied by enrichment of elements such as Al, Fe, Ti, V, Cr, Co, Ni, Ga, Th, U, Y, Zr, Ta, Nb, Hf, and REEs. While elements such as Si, Mg, Na, K, P, Ba and Rb were leached out of the profile and suffered depletion. Futhermore, elements like Ca, Mn, Sr and Cs experienced both partial leaching and fixation. Based on the results of geochemical studies, changes in pH and Eh of the weathering solutions, adsorption, presence of organic matter, function of carbonate bed rock as a geochemical barrier, existence in resistant minerals, and fixation in neomorph mineral phases played crucial role in distribution of the trace and rare earth elements in the studied ores. Consideration of the correlation coefficients among elements demonstrated that the neomorph phosphate minerals can be conceived as the potential host of rare earth elements.
Ravankhah, Moayyed, Ahmadzadeh,
Volume 28, Issue 4 (12-2020)
Abstract
Tarazoj-Soushab tectonic window is located between Tarazoj and Soushab villages at the upper corner of the northeast of 1:100,000 Hashjin sheet. This area is a part of the West Alborz Tertiary magmatic belt. Mafic igneous rocks include basaltic pillow lava and gabbro bodies and felsic igneous rocks include granite and trachytic flows. The main minerals of the gabbroic and basaltic rocks are plagioclase, olivine and clinopyroxene and the main minerals of the granitic rocks include plagioclase, orthoclase and quartz, and the trachyte consists mainly of potassium feldspar. Gabbroic and basaltic rocks show calc-alkaline nature and granitic and trachytic rocks have shoshonitic nature. Examination of chondrite and primitive-mantle normalized spider diagrams in basalts and gabbros indicates enrichment of LREEs relative to HREEs. The LILE and LREE enrichment and HREE depletion in the pattern may indicate low melting rate, high fugacity of CO2/H2O in the magma formation environment or high depth of generation of basaltic and gabbroic magma. Examination of chondrite and ORG-normalized spider diagrams in granites and trachytes indicate enrichment of light rare earth elements (LREE) and incompatible elements relative to heavy rare earth elements (HREE). These patterns show a marked depletion of Eu (especially in granites). Gabbroic and basaltic rocks are located in an oceanic environment with E-MORB basalts tendency and the granites and trachites associated with this assemblage belong to anorogenic granitoids (A-type) and subgroup A1. These features indicate that the studied outcrops in the Tarazoj-Soushab tectonic window belong to the rift-related magmatism and opening of the Paleo-Tethys ocean (Paleo-Tethys II) in the northwest of Iran.
Mrs Zohreh Jabbarzadeh, Dr Kamal Siahcheshm, Prof Ali Asghar Calagari,
Volume 32, Issue 4 (12-2024)
Abstract
The Tazekand mineralization zones, as a part of Tarom-Hashtjin metallogenic belt, is located about 45 km northeast of Zanjan city, NW Iran. Based on field study, petrography, and geochemical investigations, the lithologic composition of the intrusive rocks in the area varies from monzonite, diorite, granodiorite to gabbro, and volcanic units ranging from trachy-andesite, andesite to basaltic andesite. Delineation of diagrams of the Ishikawa alteration index (AI), chlorite-carbonate-pyrite index (CCPI) (known as alteration box plot), and the chemical alteration index (CIA) illustrated the main types and intensity of alterations in this area. Consideration of depletion and enrichment of elements by noting the enrichment factor in the alteration and mineralization zones indicates the role of high-temperature and low-pH of the altering fluids which acted as an important factor in decomposition of minerals such as plagioclase, alkali feldspar, and ferromagnesian and absence of K2O, Na2O and CaO components. The general pattern of REE distribution normalized by both chondrite and primitive mantle in altered and relatively fresh granitoid and volcanic units (as host rocks), shows a conspicuous negative slope and enrichment in LREE and large ion lithospheric elements (LILE) and depletion in HREE and high field strength elements (HFSE) during the alteration processes. Ce, Eu and Pr anomalies (Eu/Eu*, Ce/Ce*, Pr/Pr*) were investigated in ores along with fresh and altered host rocks. What can be inferred from these studies are that the changes in the behavior of rare earth elements as well as their normalized distribution pattern for each type of alteration has its own peculiar physicochemical conditions influenced by the action of multiple injections of hydrothermal fluids during both hypogene and supergene processes. The supergene processes compared to hypogene processes played very important and prominent role in development and evolution of the alteration zones in the Tazekand mineralization area