Mongolian Geoscientist 2021-12-30T00:00:00+00:00 Bayaraa Batkhishig Open Journal Systems <p>The Mongolian Geoscientist is published by the <a title="MUST" href="" target="_blank" rel="noopener">Mongolian University of Science and Technology </a>with support from&nbsp;<a title="Mongolian Geological Society" href="" target="_blank" rel="noopener">The Geological Society of Mongolia</a>.</p> <p><strong>The Mongolian Geoscientist is included on <a title="Google Scholar" href="" target="_blank" rel="noopener">Google Scholar</a>, <a title="Dimensions" href="" target="_blank" rel="noopener">Dimensions,</a>&nbsp;<a title="DOAJ" href="" target="_blank" rel="noopener">DOAJ</a> and <a title="CNKI" href="" target="_blank" rel="noopener">CNKI</a></strong></p> Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia 2021-12-29T10:03:35+00:00 Amarbayar Nomuulin Noriyoshi Tsuchiya Otgonbayar Dandar Atsushi Okamoto Masaoki Uno Undarmaa Batsaikhan Jiajie Wang <p>Serpentinization of ultramafic rocks in ophiolites is key to understanding the global cycle of elements and changes in the physical properties of lithospheric mantle. Mongolia, a central part of the Central Asian Orogenic Belt (CAOB), contains numerous ophiolite complexes, but the metamorphism of ultramafic rocks in these ophiolites has been little studied. Here we present the results of our study of the serpentinization of an ultramafic body in the Manlay Ophiolite, southern Mongolia. The ultramafic rocks were completely serpentinized, and no relics of olivine or orthopyroxene were found. The composition of Cr-spinels [Mg# = Mg/(Mg + Fe2+) = 0.54 and Cr# = Cr/(Cr + Al) = 0.56] and the bulk rock chemistry (Mg/Si = 1.21–1.24 and Al/Si &lt; 0.018) of the serpentinites indicate their origin from a fore-arc setting. Lizardite occurs in the cores and rims of mesh texture (Mg# = 0.97) and chrysotile is found in various occurrences, including in bastite (Mg# = 0.95), mesh cores (Mg# = 0.92), mesh rims (Mg# = 0.96), and later-stage large veins (Mg# = 0.94). The presence of lizardite and chrysotile and the absence of antigorite suggests low-temperature serpentinization (&lt;300 °C). The lack of brucite in the serpentinites implies infiltration of the ultramafic rocks of the Manlay Ophiolite by Si-rich fluids. Based on microtextures and mineral chemistry, the serpentinization of the ultramafic rocks in the Manlay Ophiolite took place in three stages: (1) replacement of olivine by lizardite, (2) chrysotile formation (bastite) after orthopyroxene and as a replacement of relics of olivine, and (3) the development of veins of chrysotile that cut across all previous textures. The complex texture of the serpentinites in the Manlay Ophiolite indicates multiple stages of fluid infiltration into the ultramafic parts of these ophiolites in southern Mongolia and the CAOB.</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Nomuulin Amarbayar, Noriyoshi Tsuchiya, Otgonbayar Dandar, Atsushi Okamoto, Masaoki Uno, Undarmaa Batsaikhan, Jiajie Wang Geochemistry and geochronology of granitoid rocks of the Taatsiin Gol pluton of the Khangai Complex, Central Mongolia 2021-12-29T10:20:24+00:00 Tsogoo Bayasgalan Baatar Munkhtsengel Sodnom Khishigsuren Battur Khurelbaatar <p>The Taatsiin Gol pluton is one of the major constitute the intrusive body of the Khangai Complex, and is composed the first phase of diorite, the second phase of porphyritic granite, biotite-hornblende granite, and granodiorite, and the third phase of biotite granite and alkali granite. This paper presents new geochemical and U-Pb zircon age data from intrusive rocks of the Taatsiin Gol pluton. Geochemical analyses show that the granitoid rocks of the pluton are high-K calc-alkaline, and metaluminous to weakly peraluminous I-type granites, depleted in HFSE such as Nb, Ta, Ti and Y and enriched in LILE such as Rb, Cs, Th, K and LREE, where some variations from early to later phases rock. Zircon U-Pb dating on the biotite granite of the third phase yielded weighted mean ages of 241.4±1.2 Ma and 236.7±1.4 Ma. Based on the new and previous researchers’ age results, the age of the Taatsiin Gol pluton of the Khangai Complex is 256-230 Ma consistent with the late Permian to mid-Triassic time. Although showing variated geochemical features, the rocks of the three phases are all suggested to form at an active continental margin setting, probably related to the southwestward subduction of the Mongol-Okhotsk Ocean plate during the late Permian to mid-Triassic period.</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Tsogoo Bayasgalan, Baatar Munkhtsengel, Sodnom Khishigsuren, Battur Khurelbaatar Lithological mapping using remote sensing techniques: A case study of Alagbayan area, Dornogobi province, Mongolia 2021-12-29T10:37:01+00:00 Badrakh Munkhsuren Batkhuyag Enkhdalai Tserendash Narantsetseg Khurelchuluun Udaanjargal Demberel Orolmaa Dolgorjav Munkhjin <p>This study investigated the multispectral remote sensing techniques including ASTER, Landsat 8 OLI, and Sentinel 2A data in order to distinguish different lithological units in the Alagbayan area of Dornogobi province, Mongolia. Therefore, Principal component analysis (PCA), Band ratio (BR), and Support Vector Machine (SVM), which are widely used image enhancement methods, have been applied to the satellite images for lithological mapping. The result of supervised classification shows that Landsat data gives a better classification with an overall accuracy of 93.43% and a kappa coefficient of 0.92 when the former geologic map and thin section analysis were chosen as a reference for training samples. Moreover, band ratios of ((band 7 + band 9)/band 8) obtained from ASTER corresponds well with carbonate rocks. According to PCs, PC4, PC3 and PC2 in the RGB of Landsat, PC3, PC2, PC6 for ASTER data are chosen as a good indicator for different lithological units where Silurian, Carboniferous, Jurassic, and Cretaceous formations are easily distinguished. In terms of Landsat images, the most efficient BR was a ratio where BRs of 5/4 for alluvium, 4/7 for schist and 7/6 to discriminate granite. In addition, as a result of BR as well as PCA, Precambrian Khutag-Uul metamorphic complex and Norovzeeg formation can be identified but granite-gneiss and schist have not given satisfactory results.</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Badrakh Munkhsuren, Batkhuyag Enkhdalai, Tserendash Narantsetseg, Khurelchuluun Udaanjargal, Demberel Orolmaa, Dolgorjav Munkhjin Editorial - Vol. 26, issue. 53 2021-12-29T09:54:42+00:00 Ochir Gerel <p>No Abstract in English</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Ochir Gerel Birth and Developing of Mongolian Geoscientist journal 2021-12-29T10:50:37+00:00 Yuhei Takahashi Niiden Ichinnorov Sereenen Jargalan Bayaraa Batkhishig <p>Since the publication of the first issue of Mongolian Geoscientist, in October 1996, 25 years have passed and the journal has successfully evolved over a quarter of a century into a periodical publication well-known also outside the borders of Mongolia. Background and episodes of early publications were reviewed by Y.Takahashi, N.Ichinnorov, and S.Jargalan, who were members of the JICA-IGMR project. The present status of Mongolian Geoscientist is that of an internationally peer-reviewed, open-access journal, published by the School of Geology and Mining Engineering, Mongolian University of Science and Technology, with support from the Geological Society of Mongolia; managed by Editor-in-Chief B.Batkhishig, Consultant Editorial Board member O.Gerel, and Associate Editors B.Munkhtsengel, B.Altanzul, and Kh.Tseedulam.</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Yuhei Takahashi, Niiden Ichinnorov, Sereenen Jargalan, Bayaraa Batkhishig Acknowledgement 2021-12-29T11:10:28+00:00 Bayaraa Batkhishig Baasandorj Altanzul Baatar Munkhtsengel Khuut Tseedulam <p>We sincerely thank to the journal Editors and Invited Reviewers of our open access volumes No 50, 51 and 52. They are the people who make an internationally peer reviewed, open access journal. <br />Reviewer’s helpful and constructive comments led to improvement in each manuscript and successful volumes.</p> 2021-12-30T00:00:00+00:00 Copyright (c) 2021 Bayaraa Batkhishig