Zahra Tahmasbi Articles List

List of Articles Zahra Tahmasbi

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1 - Geochemistry of pegmatitic and vein tourmalines and their formation mechanism in the Mashhad leucogranites
Farhad Zal Zahra Tahmasbi Ahmadi Noubari

The studied area is located in the Binalud Zone and comprises Mashhad leucogranites (g2) that include pegmatites and tourmaline veins. According to studies of the Mashhad leucogranites, these granites are peraluminous, highly differentiated and resulted from meltin More

The studied area is located in the Binalud Zone and comprises Mashhad leucogranites (g2) that include pegmatites and tourmaline veins. According to studies of the Mashhad leucogranites, these granites are peraluminous, highly differentiated and resulted from melting metapelites. In these granites, tourmaline can be seen in various forms of dendritic, nodules, vein and pegmatitic forms. For geochemical studies of vein and pegmatitic tourmalines, it was used microprobe analysis (EPMA), XRF and ICP- MS. Based on these analyses, pegmatitic tourmalines include schorl and vein tourmalines which are magnesium-rich- schorl and both are classified in the range of alkaline tourmalines. They have oscillatory chemical zoning and bluish green to brown pleochroism that is probably due to changes in concentration of Ti, Ca, and Fe. In the studied tourmalines, major substitutions took place including Na+(Fe+Mg)= X-Vacancy+Al and Na+(Fe+Mg)OH=Na+Al(O). Both types of tourmalines are resulted from magma differentiation with this difference that pegmatitic tourmalines show magmatic system characteristics but vein tourmalines have magmatic-hydrothermal system characteristics. These properties are related to the pegmatitic development stages and fluids obtained during their evolution. Manuscript profile
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2 - The Study of geochemical behavior of major and rare earth elements of garnet in the Darreh Vali pegmatites (North-east Boroujerd, Sanandaj-Sirjan zone)
Somaye Rahmani Zahra Tahmasbi Xin Ding Ahmad Ahmadi Khalagi

The pegmatites of Darreh Vali region is located in the north-east of Boroujerd which is a part of Sanandaj-Sirjan zone. In the Darreh Vali area, granodiorite bodies are cut by small pegmatitic dykes with NW–SE trend. The mineralogy of studied pegmatites consists of quar More

The pegmatites of Darreh Vali region is located in the north-east of Boroujerd which is a part of Sanandaj-Sirjan zone. In the Darreh Vali area, granodiorite bodies are cut by small pegmatitic dykes with NW–SE trend. The mineralogy of studied pegmatites consists of quartz, alkali-feldspar (orthoclase and microcline), plagioclase, muscovite, garnet (almandine-spessartin), andalusite, tourmaline, and apatite. Chondrite-normalized patterns of the Darreh Vali pegmatite are characterized by low enrichments of LREE relative to HREE (LaN/YbN=1.76-4.04), with a relatively flat HREE distribution, and a strong negative Eu anomaly (Eu/Eu* =0.20-0.54). Major element chemistry of garnets in these pegmatites indicates a compositional zoning with decreasing MnO and increasing FeO from core towards the rim. In the case of the Darreh Vali pegmatites, all garnet crystals contain low CaO (0.15 to 0.29 wt.%) and high MnO (10.27 to 13.18 wt.%), which are similar to magmatic garnets from pegmatitic melts. On the MnO+CaO versus FeO+MgO (in wt. %) diagram, the composition of garnets shows that they probably crystallised in contact zones of pegmatite vein and from less evolved melts. LA-ICP-MS analyses show that analysed garnets have a high HREE, low LREE contents, and strong negative Eu anomaly (Eu/Eu*=0-0.41) in the core along with positive Eu anomaly (Eu/Eu*=0-3.22) at the rim. Y, HREE, Ti, Zr, Nb, Ta, Hf, U and Mn decrease from core to rim. These core-to-rim elemental variations are attributed to increasing fluid-phase and H2O activity in magma, along with increasing magma fractionation. REE patterns and Eu anomalies in zoned garnets suggest that they probably formed in reducing to oxidizing conditions. Manuscript profile
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3 - The study of geochemical behavior of major and rare earth elements of garnet in the metamorphic rocks at Boroujerd area (Sanandaj-Sirjan Zone)
فرشته سجادی Somaye Rahmani NASIM Shamsaddini Zahra Tahmasbi Hashemi Xink Ding Ahmad Ahmadi Khalagi

Garnet–mica schist and hornfels rock units are exposed in the east and southeast of Boroujerd. These rocks consist primarily of quartz, K-feldspar, plagioclase, garnet (almandine–spessartine), chlorite, cordierite, andalusite, sillimanite, biotite, muscovite, and minor More

Garnet–mica schist and hornfels rock units are exposed in the east and southeast of Boroujerd. These rocks consist primarily of quartz, K-feldspar, plagioclase, garnet (almandine–spessartine), chlorite, cordierite, andalusite, sillimanite, biotite, muscovite, and minor amounts of apatite, iron oxides (ilmenite and magnetite), and zircon. Whole-rock geochemical analyses reveal that the dominant protoliths are pelitic rocks. Major and trace element compositions suggest that the Boroujerd pelites were deposited along an active continental margin. Garnet porphryblasts in some hornfels samples are compositionally homogeneous with respect to major, trace and rare earth elements; this is attributed to the diffusional re-equilibration at high temperatures (>600 ºC). Garnet in schists and some hornfels samples show reverse compositional zoning with increasing Mn and decreasing Fe and Mg from core to rim. Higher concentrations of Mn in garnet rims are attributed to resorption during retrogression. The presence of chlorite around garnet porphryblasts in these schists also supports resorption during retrogression. In schists, concentrations of HREE and Y in garnet decrease from core to rim. These zoning patterns are interpreted to record garnet growth in a closed system (i.e., Rayleigh fractionation of compatible elements). Core–rim variations in the concentrations of trace elements and rare earth elements in garnet in the hornfels samples is negligible. The lack of prominent zoning of these elements in garnet from hornfels is interpreted as minimal fractionation due to rapid garnet growth. Manuscript profile
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4 - Geochemistry and Mineral Chemistry of the Ahowan intrusion rocks, northeast Semnan (Central Iran)
Saeed Kamran Ahmad Ahmadi Khalaji M. Rezaei-Kahkhaei Zahra Tahmasbi
20.1001.1.17357128.1402.17.65.1.3

The study rocks outcropped in the northeast Semnan area. These rocks, composed of monzogabbro-monzodiorite, was intruded in the Eocene sedimentary and volcanic rocks. Plagioclase and clinopyroxene are the main constituent minerals of these rocks. The study rocks represe More

The study rocks outcropped in the northeast Semnan area. These rocks, composed of monzogabbro-monzodiorite, was intruded in the Eocene sedimentary and volcanic rocks. Plagioclase and clinopyroxene are the main constituent minerals of these rocks. The study rocks represent granular and poiiklitic textures. Based on EMPA data, clinopyroxenes, and plagioclases are diopside and augite and andesine, labradorite and bitonite in compositions and formed in temperatures ranged from 1104 to 1168 and less than 700 °C respectively. On the basis of tectonic discrimination diagrams, the investigated samples fall into volcanic arc domain resulted in subduction of Neothetian oceanic lithosphere beneath Central Iran block. Manuscript profile

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List of Articles Zahra Tahmasbi