Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia
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 ul...
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| Format: | Article |
| Language: | English |
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Mongolian University of Science and Technology
2021-12-01
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| Series: | Mongolian Geoscientist |
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| Online Access: | https://www.mongoliajol.info/index.php/MGS/article/view/1787 |
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| author | Amarbayar Nomuulin Noriyoshi Tsuchiya Otgonbayar Dandar Atsushi Okamoto Masaoki Uno Undarmaa Batsaikhan Jiajie Wang |
| author_facet | Amarbayar Nomuulin Noriyoshi Tsuchiya Otgonbayar Dandar Atsushi Okamoto Masaoki Uno Undarmaa Batsaikhan Jiajie Wang |
| author_sort | Amarbayar Nomuulin |
| collection | DOAJ |
| description | 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 < 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 (<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. |
| first_indexed | 2024-12-20T16:06:30Z |
| format | Article |
| id | doaj.art-e635746927324547aa2163979dcfe521 |
| institution | Directory Open Access Journal |
| issn | 2220-0622 2663-5151 |
| language | English |
| last_indexed | 2024-12-20T16:06:30Z |
| publishDate | 2021-12-01 |
| publisher | Mongolian University of Science and Technology |
| record_format | Article |
| series | Mongolian Geoscientist |
| spelling | doaj.art-e635746927324547aa2163979dcfe5212022-12-21T19:34:08ZengMongolian University of Science and TechnologyMongolian Geoscientist2220-06222663-51512021-12-01265311710.5564/mgs.v26i53.17871738Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern MongoliaAmarbayar Nomuulin0https://orcid.org/0000-0001-8176-6849Noriyoshi Tsuchiya1https://orcid.org/0000-0001-8176-6849Otgonbayar Dandar2https://orcid.org/0000-0002-7489-1710Atsushi Okamoto3https://orcid.org/0000-0001-5757-6279Masaoki Uno4https://orcid.org/0000-0002-6182-0577Undarmaa Batsaikhan5https://orcid.org/0000-0003-2678-5080Jiajie Wang6Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.School of Geology and Mining, Mongolian University of Science and Technology, Ulaanbaatar 14191, Mongolia.Graduate School of Environmental Studies, Tohoku University, Aoba 6-6-20, Aramaki Aoba-ku, Sendai 980-8579, Japan.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 < 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 (<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.https://www.mongoliajol.info/index.php/MGS/article/view/1787manlay ophiolitemulti-stage serpentinizationsouthern mongoliaserpentinite |
| spellingShingle | Amarbayar Nomuulin Noriyoshi Tsuchiya Otgonbayar Dandar Atsushi Okamoto Masaoki Uno Undarmaa Batsaikhan Jiajie Wang Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia Mongolian Geoscientist manlay ophiolite multi-stage serpentinization southern mongolia serpentinite |
| title | Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia |
| title_full | Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia |
| title_fullStr | Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia |
| title_full_unstemmed | Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia |
| title_short | Multi-stage serpentinization of ultramafic rocks in the Manlay Ophiolite, southern Mongolia |
| title_sort | multi stage serpentinization of ultramafic rocks in the manlay ophiolite southern mongolia |
| topic | manlay ophiolite multi-stage serpentinization southern mongolia serpentinite |
| url | https://www.mongoliajol.info/index.php/MGS/article/view/1787 |
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