GEOLOGICAL RESEARCH REPORT COLLECTION MYANMAR UPDATE 18-4-2023
Abstract and Figures
GEOLOGICAL RESEARCH REPORT COLLECTION MYANMAR UPDATE 18-4-2023
Frontal expansion of an accretionary wedge under highly oblique plate convergence: Southern Indo-Burman Ranges, Myanmar
Article
December 2022
Geological Society of America Bulletin
Peng ZhangShao-Yong JiangRaymond A. Donelick[...]Lianfu Mei
Isotopic niche modelling of the Pondaung mammal fauna (middle Eocene, Myanmar) shows microhabitat differences. Insights into paleoecology and early anthropoid primate habitats
April 2023Frontiers in Ecology and Evolution 11:1110331
DOI: 10.3389/fevo.2023.1110331
Lab: Hervé Bocherens's Lab (AG Biogeologie)
Sophie Gabriele HabingerSophie Gabriele HabingerOlivier ChavasseauOlivier ChavasseauStéphane DucrocqShow all 9 authors
Hervé BocherensHervé Bocherens
Timing of Syenite‐Charnockite Magmatism and Ruby and Sapphire Metamorphism in the Mogok Valley Region, Myanmar
Article
March 2020
Tectonics
M. P. SearleJoshua M. GarberBradley Hacker[...]Laurence Robb
Figures - uploaded by Myo AUNG Myanmar
Author content
All figure content in this area was uploaded by Myo AUNG Myanmar
Content may be subject to copyright.
ResearchGate has not been able to resolve any citations for this publication.
Decades of field and microscope studies and more recent quantitative geo-chemical analyses have resulted in a vast, and sometimes overwhelming, array of nomenclature and terminology associated with igneous rocks. Under the auspices of the International Union of Geological Sciences (IUGS), a group of petrologists from around the world has laboured for more than 30 years to collate these terms, gain international agreement on their usage, and reassess the methods by which we categorize and name igneous rocks. This book presents the results of their work and gives a complete classification of igneous rocks based on all the recommendations of the IUGS Sub-commission on the Systematics of Igneous Rocks. Revised from the 1st edition (1989), it shows how igneous rocks can be distinguished in the sequence of pyroclastic rocks, carbonatites, melilite-bearing rocks, kalsilite-bearing rocks, kimberlites, lamproites, leucite-bearing rocks, lamprophyres and charnockites. It also demonstrates how the more common plutonic and volcanic rocks that remain can then be categorized using the familiar and widely accepted modal QAPF and chemical TAS classification systems. The glossary of igneous terms has been fully updated since the 1st edition and now includes 1637 entries, of which 316 are recommended by the Subcommission, 312 are regarded as local terms, and 413 are now considered obsolete. Incorporating a comprehensive list of source references for all the terms included in the glossary, this book will be an indispensable reference guide for all geologists studying igneous rocks, either in the field or the laboratory. It presents a standardized and widely accepted naming scheme that will allow geologists to interpret terminology found in the primary literature and provide formal names for rock samples based on petrographic analyses. Work on this book started as long ago as 1958 when Albert Streckeisen was asked to collaborate in revising Paul Niggli's well-known book Tabellen zur Petrographie und zum Gesteinbestimmen (Tables for Petrography and Rock Determination). It was at this point that Streckeisen noted significant problems with all 12 of the classification systems used to identify and name igneous rocks at that time. Rather than propose a 16th system, he chose instead to write a review article outlining the problems inherent in classifying igneous rocks and invited petrologists from around the world to send their comments. In 1970 this lead to the formation of the Subcommission of the Systematics of Igneous Rocks, under the IUGS Commission on Petrology, who published their conclusions in the 1st edition of this book in 1989. The work of this international body has continued to this day, lead by Bruno Zanettin and later by Mike Le Bas. This fully revised 2nd edition has been compiled and edited by Roger Le Maitre, with significant help from a panel of co-contributors.
Gems & Mines of Mogôk details the gem mining methods practiced in Mogôk since the late 1800s, the licensing regulations and gem production. It illustrates the diverse cornucopia of gemstone wealth found beneath the soggy soils or embedded in the marbles of Mogôk.
Every time you turn the page you strike a bonus -the detailed description of a particular mining site illustrated with detailed topographic maps and sketches and complimented with photographs of mineral specimens and gems it produces.
For the geologist and mineralogist, this book offers facts about the diverse geology of Mogôk, accompanied by previously unpublished photographs of geological specimens collected by the author, tectonic schemes, geological models, satellite images, topographic and geological maps, providing new accounts on Mogok’s regional geology, petrology, mineralogy.
ISBN 0-940965-30-5 Hard cover, format 8.5”x11”, 353 offset pp. 1600+ color images. Contact: ted@themelis.com.
Knowledge of Trans-Himalayan tectono-magmatic evolution is critical to understanding the complex pre-collisional history of southern Eurasia active continental margin. It has been proposed that magmatic rocks of the Trans-Himalayan batholith, extending from southern Tibet to Southeast Asia, are now exposed as the Western Myanmar Arc and Central Granite Belt in Myanmar, yet origin, emplacement, and relationships of the two juxtaposed belts remain poorly constrained. In this study, 2D seismic and drilling data for the Western Myanmar Arc, zircon U-Pb age and Hf isotope and whole-rock geochemical data for magmatic rocks from the arc have been applied. Our seismic profiles, borehole stratigraphic sequences and zircon U-Pb data show that a typical arc-basin system was well developed along the western Myanmar continental margin. The magmatic arc has experienced at least three igneous events in the mid-Cretaceous (110–90 Ma), latest Cretaceous-Early Paleocene (69–64.5 Ma) and Eocene (53–38 Ma), as well as three associated uplift processes in the Late Cretaceous, Eocene and Late Oligocene. Whole-rock geochemical characteristics and zircons showing variable but predominately positive εHf(t) values, suggest a significant juvenile mantle source involving a proportion of ancient subducted sediments and juvenile crustal materials for these typical arc-related magmatic rocks. The identification of mid-Cretaceous to Paleogene magmatic rocks having positive εHf(t) values from the Western Myanmar Arc: 1) indicates that the magmatism can be correlated with the Gangdese arc within the Lhasa terrane of the southern Tibetan Plateau; 2) provides evidence for the proximal-derived model that Paleogene sediments in the Central Myanmar Basin were from the Western Myanmar Arc, but were not delivered by the paleo-Yarlung Tsangpo-Irrawaddy river system from the Gangdese arc; and 3) enables a model of eastward subduction of the Neo-Tethyan/Indian oceanic crust to reflect onset of the magmatism at the mid-Cretaceous and a long-existed back-arc extension in western Myanmar.
The Mogok metamorphic belt in central Myanmar is composed mainly of high-temperature paragneisses, marbles, calc-silicate rocks, and granitoids. The garnet-biotite-plagioclase-sillimanite-quartz and garnet-cordierite- sillimanite-biotite-quartz assemblages and their partial systems suggest pressure-temperature (P-T) conditions of 0.60-0.79 GPa/800-860 °C and 0.65 GPa/820 °C, respectively, for the peak metamorphic stage, and 0.40 GPa/620 °C for the exhumation stage. Ti-in-biotite and Zr-in-rutile geothermometers also indicate metamorphic equilibrium under upper amphibolite- and granulite facies conditions. Comparison of these estimates with previously described P-T conditions suggests that (1) the metamorphic conditions of the Mogok metamorphic belt vary from the lower amphibolite- to granulite facies, (2) metamorphic grade seems to increase from east to west perpendicular to the north-trending extensional direction of the Mogok belt, (3) granulite facies rocks are widespread in the middle segment of the Mogok belt, and (4) the granulite facies rocks were locally re-equilibrated at lower amphibolite facies conditions during the exhumation.
Before the India–Asia collision, Neotethyan subduction gave rise to an Andean-type convergent margin on the southern margin of Asia. To investigate the spatial and temporal distribution of the subduction-related magmatism, we undertook a combined determination of zircon U–Pb ages and Hf isotopes of Mesozoic to Paleogene intrusive and volcanic rocks from southern Tibet to Myanmar to characterize the two parallel magmatic belts that have previously been considered separately. One belt extends from the Gangdese Batholith in the Southern Lhasa sub-terrane to the Lohit Batholith, the Sodon Pluton and the Popa–Loimye Arc in the West Burma Block, and the other from the Central Lhasa Plutonic Belt to the Bomi–Chayu Batholith, the Dianxi Batholith and the Shan Scarps Batholith in central Myanmar. The Gangdese belt, as the main arc component, consists typically of I-type granitoids that contain magmatic zircons showing positive ε Hf ( t ) values. In contrast, the Central Lhasa Plutonic Belt belt is dominated by S-type granites in which most zircons show negative ε Hf ( t ) values suggesting the involvement of older continental crust in their petrogenesis. The distinct geochemical characteristics indicate not only distinct tectonic settings of their genesis but also the diverse nature of the crust forming the exotic continental ribbons amalgamated to Asia.
Supplementary material: Details of sample locations and analytical results are available at: https://doi.org/10.6084/m9.figshare.c.4311485
The Mogok metamorphic belt of Paleogene age, which records subduction‐ and collision‐related events between the Indian and Eurasian plates, lies along the western margin of the Shan plateau in central Myanmar and continues northwards to the eastern Himalayan syntaxis. Reaction textures of clinohumite‐ and scapolite‐bearing assemblages in Mogok granulite facies metacarbonate rocks provide insights into the drastic change of fluid composition during exhumation of the collision zone. Characteristic high‐grade assemblages of marble and calc‐silicate rock are clinohumite +forsterite+spinel+phlogopite+pargasite/edenite+calcite+dolomite, and scapolite+ diopside+anorthite+quartz+calcite, respectively. Calculated petrogenetic grids in CaO‐MgO‐Al2O3‐SiO2‐H2O‐CO2 and subsets of this system were employed to deduce the pressure‐temperature‐fluid evolution of the clinohumite‐ and scapolite‐bearing assemblages. These assemblages suggest higher temperature (> 780–810 °C) and XCO2 [= CO2/(CO2+H2O) > 0.17–0.60] values in the metamorphic fluid for the peak granulite facies stage, assuming a pressure of 0.8 GPa. Calcite grains commonly show exsolution textures with dolomite particles, and their reintegrated compositions yield temperatures of 720–880 °C. Retrograde reactions are mainly characterized by a reaction zone consisting of a dolomite layer and a symplectitic aggregate of tremolite and dolomite grown between clinohumite and calcite in marble, and a replacement texture of scapolite by clinozoisite in calc‐silicate rock. These textures indicate that the retrograde reactions developed under lower temperature (< 620 °C) and XCO2 (< 0.08–0.16) conditions, assuming a pressure of 0.5 GPa. The metacarbonate rocks share metamorphic temperatures similar to the Mogok paragneiss at the peak granulite facies stage. The XCO2 values of the metacarbonate rock at peak metamorphic stage are, however, distinctly higher than those previously deduced from carbonate mineral‐free paragneiss. Primary clinohumite, phlogopite and pargasite/edenite in marble have F‐rich compositions, and scapolite in calc‐silicate rock contains Cl, suggesting a contrast in the halogen compositions of the metamorphic fluids between these two lithologies. The metamorphic fluid compositions were probably buffered within each lithology, and the effective migration of metamorphic fluid, which would have extensively changed the fluid compositions, did not occur during the prograde granulite facies stage throughout the Mogok metamorphic belt. The lower XCO2 conditions of the Mogok metacarbonate rocks during the retrograde stage distinctly contrast with higher XCO2 conditions recorded in metacarbonate rocks from other metamorphic belts of granulite facies. The characteristic low XCO2 conditions were probably due to far‐ranging infiltration of H2O‐dominant fluid throughout the middle segment of the Mogok metamorphic belt under low‐amphibolite facies conditions during the exhumation and hydration stage.
This article is protected by copyright. All rights reserved.
Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar arms readers with a comprehensive overview of the geography, geology, mineral potential and tectonic plate activity of Myanmar. The book focuses on the nature and history of the structural belts and terranes of Myanmar, with particular emphasis on the mineral deposits and their relationship to stratigraphy and structure. The country has a long history of plate tectonic activity, and the most recent plate movements relate to the northward movement of the India plate as it collides with Asia. Both of these are responsible for the earthquakes which frequently occur, making the country a geologically dynamic region. Additionally, Myanmar is rich in mineral and petroleum potential and the site of some of Southeast Asia's largest faults. However, many geoscientists are only recently becoming familiar with Myanmar due to previous political issues. Some of these barriers have been removed and there is emerging international interest in the geology and mineral deposits of Myanmar. This book collates this essential information in one complete resource. Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar is an essential reference for economic geologists, mineralogists, petroleum geologists, and seismologists, as well as geoscience instructors and students taking related coursework. Provides an accessible history of the geological research and mineral exploration and extraction conducted in Myanmar and an overview of its rich mineral resources. Presents the historical and current plate tectonic activity in the region, offering seismologists and geophysicists a guide to Myanmar's structural geology and risk for earthquake activity. Richly illustrated with more than 100 maps, diagrams and photographs to capture the geology of Myanmar and aid in the retention of key concepts. Focuses on the nature and history of the structural belts and terranes of Myanmar.
Production from the 'tract', located approx 700 km N of Rangoon, is largely from alluvial deposits. Topics covered include: history and production, geology, mining methods, gemmology of the ruby, and famous rubies from the tract. -R.V.D.