Geochronologic Constraints on the Magmatic Underplating of the Gangdisê Belt in the India-Eurasia Collision: Evidence of
The Gangdisê Belt, located in the southern Tibetan Plateau, is a key geological structure resulting from the ongoing India-Eurasia collision. Understanding the magmatic processes beneath this belt is crucial for unraveling the tectonic evolution of the region. Geochronologic constraints play a pivotal role in deciphering the timing and duration of magmatic underplating, shedding light on the thermal and rheological state of the lithosphere. This article discusses the geochronologic evidence of magmatic underplating beneath the Gangdisê Belt and its implications for the India-Eurasia collision.
The India-Eurasia collision, which began approximately 50 million years ago, has led to the convergence and subsequent underthrusting of the Indian plate beneath the Eurasian plate. The Gangdisê Belt, situated at the northern edge of the Indian plate, has been significantly affected by this collision, experiencing intense deformation, metamorphism, and magmatism. The presence of magmatic underplating beneath the Gangdisê Belt is supported by geophysical and geochemical evidence, including seismic tomography, gravity anomalies, and the composition of volcanic rocks.
Geochronologic studies have provided valuable insights into the timing and duration of magmatic underplating beneath the Gangdisê Belt. Radiometric dating techniques, such as U-Pb dating of zircon and Ar-Ar dating of minerals, have been used to determine the ages of magmatic rocks associated with underplating. These studies have revealed that magmatic activity beneath the Gangdisê Belt occurred in multiple stages over a prolonged period, spanning from the Paleocene to the Miocene.
One of the key geochronologic constraints on the magmatic underplating of the Gangdisê Belt is the identification of different magmatic episodes and their ages. For example, zircon U-Pb dating of granitic rocks in the Gangdisê Belt has yielded ages ranging from approximately 55 to 15 million years ago, indicating episodic magmatic activity over a 40 million year period. Similarly, Ar-Ar dating of mafic and ultramafic rocks has provided ages of approximately 23 to 16 million years ago, indicating a more recent phase of magmatism.
The geochronologic constraints on the magmatic underplating of the Gangdisê Belt have important implications for understanding the tectonic evolution of the region. The episodic nature of magmatic activity suggests that the underplating process was not continuous but occurred in distinct pulses, possibly in response to changes in the subduction dynamics or the thermal regime of the lithosphere. Additionally, the presence of magmatic underplating may have played a role in the thickening and uplift of the Tibetan Plateau, contributing to its high elevation.
In conclusion, geochronologic constraints provide valuable insights into the magmatic underplating of the Gangdisê Belt in the India-Eurasia collision. The episodic nature of magmatic activity and the prolonged duration of underplating highlight the complex tectonic processes at play in the region. Further geochronologic studies are needed to refine our understanding of the timing and duration of magmatic underplating and its role in the tectonic evolution of the Tibetan Plateau.
