Paleogeographic Evolution of Southeast Asia: Geochemistry and Geochronology of the Katha-Gangaw Range, Northern Myanmar

Abstract

The Mogok continental foreland region and Katha-Gangaw range (KGR) are located in the north-central section of the Myanmar plate, which is a component of the Eurasian plate. The origin of KGR, exposed along northern Myanmar (SE Asia), is still up for argument, despite numerous prior studies. Based on the petrography, geochemistry, and detrital zircon U-Pb geochronology of metamorphic rock samples, the current study focuses on the tectonic evolution of the KGR. The study also emphasizes the phenomenon of microcontinents rifting from the Gondwanan supercontinent and their subsequent amalgamation with Asia. Detrital zircon ages from four samples in the southern region of KGR peak at 634 Ma, 525 Ma, 290 Ma, and 248 Ma, and two samples yielded > 40% of the grains of younger than 400 Ma. Similar results were obtained from three samples (out of six) from the central region of the KGR. All of the samples from the northern part of KGR are older than 400 Ma, with the exception of MT-02A, which contains nearly all of the younger grains. These younger peaks are identical to the zircon U-Pb ages of the Indochina block, the Sibumasu block, and the Pane Chaung Formation of the Myanmar plate, as well as the Langjiexue Formation (southeastern Tibet). This similarity raises the possibility of either these units being a source region of strata in northern Myanmar or sharing a similar source. The geochemistry of metamorphic rocks samples from KGR revealed loss-on-ignition (LOI) values of 0.29–4.18 wt%, emphasizing the modest to moderate alteration. The samples are enriched in large-ion lithophile elements (LILEs), and depleted in high-field strength elements (HFSEs). All metamorphic samples are peraluminous, indicating the linkage with collisional orogenies. This result is most comparable to upper continental crustal provenance. Hence, the metamorphic rocks in KGR regions must be associated with the crustal materials.