Number 69 Volume 18

Open Access Article

1 - Geochemistry and mineral chemistry of ultramafic rocks in the Koopan area, south of Bavanat (Fars Province)
Maryam Zurmand Sangari Ahmad Ahmadi Khalaji Kamal Noori Khankahdani Zahra Tahmasbi

The studied area is located in the high Zagros zone and it is considered a part of the Neyriz ophiolite. In this area, the ophiolitic complex is small coloured melanges include radiolarite cherts and serpentinized ultrabasic rocks. The main lithological unit is serpen More

The studied area is located in the high Zagros zone and it is considered a part of the Neyriz ophiolite. In this area, the ophiolitic complex is small coloured melanges include radiolarite cherts and serpentinized ultrabasic rocks. The main lithological unit is serpentinized ultrabasic rocks, which have a variety of colors from dark to light brown and dark to light green. These ultrabasic rocks have composed of olivine, pyroxene, amphibole, opaque, serpentine and spinel. Olivines have been highly altered to serpentine and pyroxenes to bastite. Based on whole rock chemistry, the studied rocks are basic and ultrabasic cumulates type (lherzolite-harzburgite) with a composition close to the average composition of the mid-ocean ridge basalt (MAR). Based on mineral chemistry, pyroxenes are calcic type and in the range of diopside and augite, and amphiboles are calcic and actinolite type. Pyroxenes have crystallized under conditions of low oxygen fugacity, temperature higher than 910 °C (1100 - 1200 °C) and pressure more than 2 kbar (2 to 10 kbar). Amphiboles have crystallized at a temperature below 700 °C and a pressure less than 1 kbar. Based on the geochemical characteristics and mineral chemistry, the ultrabasic rocks in the Koopan area were formed in a subduction zone. Manuscript profile

Open Access Article

2 - Estimating the shear sonic log using machine learning methods, and comparing it with the obtained data from the core
Houshang Mehrabi Ebrahim Sfidari Seyedeh Sepideh Mirrabie Sadegh Barati Boldaji Seyed Mohammad Zamanzadeh

Machine learning methods are widely used today to estimate petrophysical data. In this study, an attempt has been made to calculate shear sonic log (DTS) from other petrophysical data using machine learning methods and compare it with the sonic data obtained from the More

Machine learning methods are widely used today to estimate petrophysical data. In this study, an attempt has been made to calculate shear sonic log (DTS) from other petrophysical data using machine learning methods and compare it with the sonic data obtained from the core. For this purpose, computational methods such as Standard Deviation, Isolation Forest, Min. Covariance, and Outlier Factors were used to normalize the data and were compared. Given the amount of missing data and box plots, the Standard Deviation method was selected for normalization. The machine learning methods used include Random Forest, Multiple Regression, Boosted Regression, Support Vector Regression, K-Nearest Neighbor, and MLP Regressor. Multiple regression had the lowest evaluation index (R2=0.94), while Random Forest regression had the highest correlation between the estimated shear sonic log and the original shear sonic log with an evaluation index of 0.98. Therefore, Random Forest regression was used for the final estimation, and to prevent data generalization or overfitting, the GridSearchCV function was used to calculate optimal hyperparameters and final estimation. The estimated sonic log showed a very high similarity with the core data. Manuscript profile

Open Access Article

3 - Distribution pattern of gold and Rare Earth Elements in different and mineralized zones of Lakhshak deposit (Sistan Suture zone)
Nasim Heydarian Dehkordi Sh. Niroomand Hossein Ali Tajeddin

Lakhshak deposit is located in the southwestern part of the Sistan Suture zone and 28 km northwest of Zahedan. The exposed rock units include granitoid intrusion and dacite-rhyolite dykes with Oligocene age and calc schist and quartz schist with Eocene age, which More

Lakhshak deposit is located in the southwestern part of the Sistan Suture zone and 28 km northwest of Zahedan. The exposed rock units include granitoid intrusion and dacite-rhyolite dykes with Oligocene age and calc schist and quartz schist with Eocene age, which have metamorphosed to the green schist facies. This complex has transformed under the influence of a shear zone with a northeast-southwest trend. The composition of intrusive masses placed in the range of granodiorite based on lithological charts. Based on petrographic studies, the minerals that make up the intrusive masses include quartz, alkali feldspar, plagioclase, biotite, sericite, muscovite, iron oxides and calcite. Among the most important types of alteration, we can mention sericite, sulfide, siliceous and carbonate alterations. Analysis of the distribution patterns of rare earth elements in the shear zone samples shows the enrichment of REE in the central parts of the shear zone (severe degrees of alteration and deformation) compared to the foot wall and hanging wall units (weak degrees of alteration and deformation) of the shear zone. The distribution pattern of these elements includes the enrichment of LREE compared to HREE, which can attributed to regional metamorphism at the green schist facies and the circulation of CO2 and SO42- fluids in the Lakhshak shear zone. In addition, the presence of positive and negative Eu anomalies in the shear zone indicates two different stages of alteration. Weak to moderate alteration has led to the creation of positive Eu anomaly and advanced alteration has caused severe decomposition of plagioclase as the main source of Eu and negative Eu anomaly. Manuscript profile

Open Access Article

4 - Geochemistry of Central part of the Neo-Tethys Suture zone serpentinites (From NW Iran to Iraqi Zagros and Eastern Anatoly)
monir modjarrad Mohsen Moayyed

The subduction and closure of the vast Neo-Tethys ocean between the Arabian and Eurasian plates has left numerous ophiolitic traces, the unique position of Iran in its central part is noticeable. The lack of information, right on the border of Iran with Iraq and Turke More

The subduction and closure of the vast Neo-Tethys ocean between the Arabian and Eurasian plates has left numerous ophiolitic traces, the unique position of Iran in its central part is noticeable. The lack of information, right on the border of Iran with Iraq and Turkey, due to security considerations, has so far prevented the overview of this suture zone in the northwestern border of Iran. Adding Gysian ophiolite in southern Urmia as a missing link in this stretch can partially cover this lack of information. A comparative study of whole rock chemistry of serpentinites in the central part of the Neo-Tethys ophiolites, considering several sectors from Iran (Kamyaran, Marivan and Gysian), Iraq (Penjwin and Mawat) and Turkey (Guleman and Osmanie) in this article, indicates that they belong to subducted serpentinites, whether they were originally formed in the fore-arc environment or the at abyssal oceanic environment. Composition of the serpentinites of the central part of the suture zone is similar to the average global serpentinites which have mostly lizardite/chrysotile. All of them show depletion of Mg resulting sea floor alteration during serpentinization. The mentioned point may be caused to data deviation from abyssal peridotites field. Considering that the transition metals contents the confirmed the above setting. Almost all of the studied serpentinites are from subducted type which indicates refertilization of LILE evidences as a result of rock/fluid interaction through serpentinization. Manuscript profile

Open Access Article

5 - Geochemistry and petrogenesis of the subvolcanic domes of the northern domain of the Sabzevar ophiolitic belt, north east of Iran
E. Mohammadi Gorji Ghasem Ghorbani Hadi Shafaii Moghadam

Andesitic-dacitic subvolcanic domes of Nudeh Enghelab and Kuh Kamartang are located in the northern domains of the Sabzevar ophiolitic belt, and in the northeast part of the Central Iran structural zone. Geochemically, the studied rocks exhibit a metaluminous, calc-al More

Andesitic-dacitic subvolcanic domes of Nudeh Enghelab and Kuh Kamartang are located in the northern domains of the Sabzevar ophiolitic belt, and in the northeast part of the Central Iran structural zone. Geochemically, the studied rocks exhibit a metaluminous, calc-alkaline to high k-calc-alkaline nature, and are enriched in LILE and LREE and depleted in HFSE, HREE and negative anomaly in TNT elements, and have formed in an environment related to subduction zone. With attention to their other geochemical characteristics, such as a silica content (SiO2>61wt%), Al2O3>15wt%, MgO<2.2wt%, Na2O>3.3wt%, Sr/Y>24, La/Yb>8, can be classified these rocks as high silica adakites. The petrographical, geochemical and isotopic ((87Sr/86Sr)i=0.7047-0.7045, ƐNdi=6.02-6.10) characteristics display that the studied high silica adakites have been originated from partial melting of subducted oceanic slab of Neo-Tethys (Sabzevar sea/ocean sub-branch) under the Turan plate in amphibolite to garnet amphibolite facies and during the ascent to high levels, they show very little assimilation and contamination with continental crust. Manuscript profile

Open Access Article

6 - Application of Sporomorph EcoGroups (SEGs) and parent plants of miospores in palaeoenvironmental recontruction of the Qadir Member (Nayband Formation), south of Tabas
Firoozeh Hashemi Yazdi F. Sajjadi Hezaveh Narges Sadat Mirpoor Shah Abolghasemi Zahra Mohammadi Manesh Mohsen Allameh

Sporomorph EcoGroups data and the relevant plant communities are considered as a possible routine used to draw palaeoecological inferences for their host strata. Occurrence of high abundant and diverse miospores in the Qadir Member (Nayband Formation), from the explorat More

Sporomorph EcoGroups data and the relevant plant communities are considered as a possible routine used to draw palaeoecological inferences for their host strata. Occurrence of high abundant and diverse miospores in the Qadir Member (Nayband Formation), from the exploratory well no. 954 (Exploratory Area of Parvadeh 4), south of Tabas, central Iran allows for this method to be used to obtain certain palaeoecological implications. By classifying spores and pollens (sporomorphs) in Sporomorph EcoGroups (SEGs), all six plant ecogroups (including plants adapted to Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced) were identified in examined material. The high ratio of warmer/cooler sporomorphs and the low ratio of drier/wetter sporomorphs suggests deposition under a moist, ±warm climate during the Late Triassic in south of Tabas. From the investigation of miospore parent plants, it was approved that, in descending order, pteridophyta (44%), cycadophyta (34%), coniferophyta (9%), lycophyta (8%), pteridospermophytes (2%), ginkgophytes (2%) and bryophyta (1%) were surrounded the environment of the studied formation. Notable abundance of fern spores (Kyrtomisporis and Foveogleicheniidites) and cycads pollen (Ovalipollis and Ricciisporites) in the palynofloras studied indicate the predominance of warm to semi-warm climate with high humidity. Paleogeographic position of Iran during the Late Triassic in the southern active margin of Eurasia (Turan Plate) tends to support this palaeoclimate generalization. Manuscript profile

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