5/31/2023 0 Comments Convergent divergent transformThe EM1 and EM2 basalts display positive Sr anomalies and elevated Pb/Ce and Th/La ratios, respectively. Whereas the basalts south of the boundary show isotopic features similar to Enriched Mantle type 1 (EM1) ocean island basalts. The basalts north of the boundary show isotopic features similar to Enriched Mantle type 2 (EM2) ocean island basalts. Based largely on Sr-Nd-Pb isotope systematics, it was found that the sources of basalts from Central and Southern Vietnam are chemically distinct forming a sharp boundary at 13.5°N. To place constraints on the origin of the intraplate volcanism in SE Asia, new geochronological and geochemical data for Cenozoic basalts in Vietnam are presented. Two contrasting models have been proposed to explain the mantle upwelling and volcanism in this region collision of the Indian and Eurasian continents or subduction of the Pacific or Indo-Australian oceanic lithosphere. Vietnam is a major field of Cenozoic volcanism in Southeast Asia. This chapter provides a brief introduction to the history and the workings of plate tectonics. As we will see in this book, plate tectonics is intertwined with ocean tides in unexpected ways. Plate tectonics dictates how the surface of the planet changes, how supercontinents break and come together, and how new oceans form and old ones close. The idea of surface mobility was first solidly proposed by Alfred Wegener in the start of the 20th century, but it took another 50 years for a unified theory of the solid earth to emerge. Many of the fundamental geological phenomena occur along the plate's boundaries, such as earthquakes and volcanoes, and the plates’ movement gives rise to a number of fundamental geological processes that include mountain building and the supercontinent cycle itself. It describes that the surface of the Earth is divided into several lithospheric tectonic plates that move in relation to each other and over the less viscous asthenosphere. Plate tectonics is the unifying theory of solid earth sciences.
0 Comments
Leave a Reply. |