![]() Image CC Divergent Plate Boundaries and MineralisationĪs the seafloor splits apart, the hydrothermal activity causes deposits of both sulphides and metalliferous sediments along flanks of ridges. If we have a clear understanding of the location of ancient plate boundaries, it’s easier to predict where regional mineralisation may occur today. However, for the exploration geologist, it is not just about where plate boundaries are now – it’s about where they were many hundreds of millions of years ago. These rocks become the source of many of our largest mineral deposits. Plate boundaries are also a way for deep-seated rocks from the mantle to find a way to the near-surface. The energy released along boundaries results in volcanic and hydrothermal activity that creates the right conditions for many minerals to be concentrated. What happens along plate boundaries is critical for mineral formation. The San Andreas fault in California is the best known example. A transform plate boundary is where two plates slide alongside each other.The Himalayas being the most spectacular example, formed as the Indian plate slams into the southern edge of the Eurasian plate. Convergent plate boundaries also create mountains when two plates of equal density collide. The Indonesian islands of Sumatra, Java, Bali and others formed from the collision of the Australian plate which is being forced under the Eurasian plate. Subduction zones are marked by a deep ocean trench with a line of volcanoes on the continent, such as the Andes where the Nazca plate is sliding under the South American plate. In subduction zones, the denser plate is forced under the less dense plate. A convergent plate boundary is where plates collide.Undersea examples include mid-ocean spreading centers and the “ black smokers” of the mid-Atlantic and northwest Pacific. Iceland is the best-studied example, as it’s conveniently above sea level. ![]() A divergent plate boundary is where tectonic plates are moving apart, usually along mid-oceanic ridges.There are three main types of plate boundaries: Three types of plate boundaries: Convergent, Transform and Divergent. If the plates suddenly stopped moving and no new crust was created, the whole world would become one gigantic ocean, as the continental crust would get eroded down to below sea level. Plate boundaries are crucial, as they are where new land is created. Oceanic crust gets thicker and colder the further away it is from a mid-ocean ridge. Oceanic plates are thinner, denser and made of basaltic rock, while the continental plates are thicker, less dense and made of granitic rock. The Earth’s topmost layer, called the crust, is broken up into pieces called tectonic plates. Red arrows indicate the direction of plate movement. The energy released along a plate boundary results in volcanic and hydrothermal activity that creates the right conditions for mineral concentration. It also explains why the Himalayas are the highest mountains in the world while the highest peak in Australia is barely over 2000m! Plate tectonics is the theory that explains why there are lots of volcanoes in Iceland and Japan, but far fewer in Russia and Africa. The physics is simple: something’s gotta give, and there are probably going to be fireworks – or at least volcanic eruptions and earthquakes! But along with the destruction comes the creation of many of the mineral deposits we rely on to support modern life. The most unstable areas of all are the plate boundaries, where giant crustal plates collide. The earth that we stand on, and think of as fixed, is anything but. In this model, the descending oceanic slab does not slide directly under the overriding plate but instead rolls back, pulling the overlying plate seaward.The world is a dynamic place. Some scientists have proposed a subduction mechanism called oceanic slab rollback creates extension faults in the overriding plates. In some subduction zones, tensional forces working on the continental plate create a backarc basin on the interior side of the volcanic arc. The forearc basin experiences a lot of faulting and deformation activity, particularly within the accretionary wedge. This subduction zone is ocean-ocean subduction, though the same features can apply to continent-ocean subduction.Īll subduction zones have a forearc basin, a feature of the overriding plate found between the volcanic arc and oceanic trench.
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