Brief Introduction
Lushan region has gone through three main different geological development stages during the long geological time.
Continental crust forming marine development stage(2500-800Ma)
Lushan region belong to a marine trough during 2500-1800Ma.The trough in the area is closed by compression around 1800Ma.Meanwhile the sedimentary and volcanic rocks in the trough were intensively metamorphosed and deformed.The continental crust crystallized basement is composed of the metamorphosed and deformed rock.The region rifted into a sea again during 1800-1000Ma.The region became the“pacific type”active continental margin during 1000-850Ma,in which the continental slope,marginal sea,volcanic arc,trench,abyssal sea occurred successively from inner to outer.Lushan region was located in the marginal sea during that time.The collision between volcanic arc and continent plate happened during 850-800Ma and the sedimentary and volcanic rocks in the sea were strongly metamorphosed and deformed,which led to the formation of continental folded basement.A large number of granite intrusions and volcanic eruption developed during the collision.
2.platform epicontinental sea stage(800-200Ma)
The crustal movement in Lushan region is relatively weak during 800-200Ma,which made the region became a broad epicontinental sea through the prolonged denudation and planation of previous mountains.Abundant animal groups occurred in seawater.The crust was uplifted into continental land at 200Ma,the seawater gone never come again.
3.Basin-range development stage(200Ma-today)
Crust movement activity in Lushan region increased obvious again after 200 Ma,which is marked by faults,magmatic intrusions,basin-range interval arrangement.Lushan region was in the intensive extension state during 95-65Ma,bring about a huge low angle main detachment fault which caused the high-grade metamorphic rock underlying the paleo-Poyang Lake in the depth of 15-20 kilometers slip to the surface,so the metamorphic core complex and paleo-Poyang Lake basin were formed.The embryonic form of the Lushan fault-block mountain developed during 65-23.3 Ma,the neighboring area depressed into lake.The Lushan fault-block mountain uplifted rapidly during 23.3-3 Ma.When the great Quaternary Glaciations occurred,Lushan had been a lofty block mountain.
