Sin título

1. ·

   • Transform boundries
     • Transform boundaries are where two plates are moving laterally past one another, like the famous San Andreas fault in California.
   • Conclusion
     • What happens along plate boundaries is critical for mineral formation. Plate tectonics provides a basis for understanding the distribution and origin of mineral deposits. The relationship of plate tectonics and mineral deposits is significant on three counts which is the following: Geological processes operating due to energy released at plate boundaries control the process of mineral deposition, mineral deposits form in particular tectonic settings which are governed by plate tectonics and reconstruction of fragmented continents can provide a useful basis for exploration of new mineral deposits. The energy released along boundaries, results in volcanic and hydrothermal activity that creates the right conditions for many minerals to be concentrated. Plate boundaries are also a way for deep-seated rocks from the mantle to find a way to the near-surface. These rocks become the source of many of our largest mineral deposits.
   • References
     • • Hein, R. J. & Mizell, K., 2013. Hydrothermal systems and mineralization of volcanic arcs: Comparison of West Pacific and Mediterranean arcs. Karlovassi, U.S. Geological Survey, pp. 216-223. • Rafferty, J. P., 2011. Encyclopaedia Britannica. [Online] Available at: https://global.britannica.com/science/back-arc-basin [Accessed 30 January 2016]. • Robb, L. J., 2005. Introduction to Ore-Forming Processes. USA: Blackwell Publishing Company. • Sawkins, F. J., 1976. Metal Deposits Related to Intracontinental Hotspot and Rifting Environments. The Journal of Geology, 84(6), pp. 653-671. • Skinner, B. J. & Porter, S. C., 1987. Physical geology. John Wiley & sons New York, 24(2), pp. 160-161. • Stern , R. J., 2002. Subduction Zones. Reviews of Geophysics, 40(4), pp. 1-13.

2. Tectonic plate boundaries are extremely dynamic places. At these boundaries volcanoes, earthquakes, mountains, and important mineral resources occur. The mineral deposits formed at tectonic plate boundaries are heavily dependent on the volcanic activity in these areas.

   • Introduction

3. Divergent boundaries

   • When two plates are moving away from each other its called Divergent boundaries and they are mostly located under oceans (sea floor spreading).
   • There are many earthquakes and vulcanoes along these ridges. a Low-pressure zone is created where the two plates move away from each other and magma can rise to the surface. The hot magma contains high concentrations of potentially valuable metals. Water percolating through the rocks leeches the metals and further concentrates them in valuable deposits. These magmas heat the water already circulating through the rock, creating hot hydrothermal fluids. Hydrothermal fluids circulating at divergent boundaries form dramatic black smokers on the seafloor that are abundant in sulfur-containing minerals. Within the past decade, mining companies have begun extracting these resources from under two miles deep of ocean water.
   •  Hydrothermal activity at the ridges results in Sulfide deposits and Metalliferous sediments on the flanks of ridges. Important metallic deposits formed are Fe, Zn, Cu, Pb, Au and Ag. Example: In the Red Sea metalliferous sediments containing Fe, Zn and Cu are being deposited.  Mn oxide deposits are important at some ridges. Example: the TAG Hydrothermal field on the Atlantic Ridge.  Ultramafic rocks in ophiolites containing asbestos, chromite and nickel ores. These are generally accessible in Phanerozoic orogenic belts to which sites they have been transported due to plate movement.  Podiform chromite deposits associated with serpentinized ultramafic rocks.  Cyprus Type massive sulfide deposits (Cu-Fe rich) are also associated with ophiolites and represent hydrothermal deposits formed at ocean ridges. (geology In, (2013). Tectonic Settings of Metal Deposits.)
     • DEPOSITS AT OCEANIC RIDGES (DIVERGENT PLATE MARGINS)

4. Convergent boundries

   • Collision zone - continental
     • A collision zone is a convergent margin in which two continents have collided. As continental lithosphere have a relative low density it is usually not subducted, this results in orogenesis involving folding and thrust faulting as the blocks of continental crust pile up against each other. Ophiolite obduction may occur at collisional zones causing felsic magma to rise and results in LILE element mineralization. Orogenic gold as wel as Sn-W-U deposits may occur at collisional zones. MVT deposits and Deposits associated with continental rifts are also related to Orogenesis. Deposits genetically related to collision zones are hydrocarbons which may accumulate in foreland basins. Exmple is the Persian Gulf SW of the Zagros Suture in Iran
   • Convergent boundaries are where two plates are moving towards one another. Plate convergence normally results in subduction, which is where one plate moves beneath the other
   • Lithospheric plates moving in the direction of one another. Subduction of plates is when oceanic crust and the lithosphere under it, together with the sediments collected on the oceanic plate return to the mantle. Continental crust can also be subducted but is not as common as oceanic plates being subducted. Metallic deposits are commonly found at convergent plat boundaries. The subduction of an oceanic plate under a continental plate mostly form economic deposits by forming arc-trenches hot spots, arc volcanos and back-arc basins.
   • Arc-trenches
     • This form where a subducting plate and the overriding lithosphere collide and pulls down a small part of the overriding lithosphere forming a trench, this is also known as the distance between the arc and the trench.
   • Hot spots (Intraplate volcanism):
     • This is volcanism that arises within tectonic plates and is not necessarily related to plate margins. Intraplate volcanism occurs usually because of a mantle plume rising hot, less dense magma from the mantle through convection. A wide variety of ore deposits can typically form in this setting.
   • Arc-volcanos
     • This refers to the chain of volcanoes that form above the subducting plate, if this occurs offshore its known as an island-arc. The subducted plate, pulling down a piece of the lithosphere, will melt at a specific depth. This subducting plate will subduct the lithosphere together with sediments and fluids (volatiles). This fluids contributes to the hydrothermal fluids and lower the melting point in some cases, and thus contributes to huge hydrothermal systems and mineralization of ores in volcanic-arcs. This and partial melting contributes to the concentration of a wide variety metals that extrudes as a volcano and forms an island rich in metals (like gold, silver, copper and barite). Endless amounts of deposits can form from both hydrothermal and igneous processes like orogenic gold, porphyry deposits (Cu-Mo, Sn-W), epithermal deposits and skarn deposits.
   • Back-arc basins:
     • Back-arc basins are associated with subduction zones and volcanic-arcs, and are usually found to be a basin forming behind the volcanic-arc. This can be sites of significant hydrothermal activity. Back-arc basins provides a perfect conditions to trap organic matter that prevents oxidation, and can produce petroleum within the right geothermal heat facilities. Deposits like tin deposits, lead-zinc-copper deposits, lead-zinc deposits, copper nickel sulphides deposits and massive sulphide copper deposits.
   • Significant deposits associated with convergent boundaries
     • Base metals ( Cu,Pb, Zn, Mo) • Presious metals (Au, Ag, Pt) • Porphyry copper deposits • Sn deposits • Cu-Ag and Ag veins • Contact metasomatic Fe-deposits • Other metals

5. Plate tectonics are where the Earth's crust is broken into rigid plates that slowly move around the surface of the planet and it is broken into several pieces to cover the Earth. The plates move around because they are riding on the slightly molten mantle

   • What is plate tectonics?

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