Tectonic Characteristics Of Luozha Fault And Its Control Of Mineral Resources

The Himalayan orogen is the youngest and most typical orogen in the world.It was formed by a collision of Indian plate and the Asian continent between 70 and 50 Ma.Since the collision,the crust of Himalayan orogen is greatly reduced.In the Miocene,while the crust shortening and thickening,the Himalayan orogen also occurred in a large stretch of movement.Both constitute a complex evolutionary process,and formed a complex geological structure in the southern Tibet.Collision orogeny also caused the mineralization of antimony,antimony gold,antimony lead-zinc polymetallic deposits in southern Tibet,where has been widely regarded as an advantageous zone for finding antimony gold deposits.Luozha fault is located in Himalayan block in Gangdise-Himalayan orogenic system.It is the same fault with Dingri-Gangba fault in the area,and it is an important active fault of the South Tibetan Detachment System.The main antimony gold deposits in the southern Tibet are distributed near the Luozha fault.Through the geological survey of a number of lines across the Luozha fault,we had seen many tectonic phenomenons,and divided the fault into main brittleness fault,toughness fault and branch brittleness fault.Combined with indoor analysis and previous research results,we divided the stress evolution of the Luozha fault into six periods.First,NE-SW extrusion in Paleogene,manifested as the retrograde relics in the main brittleness fault and fold – and-thrust belt in the upper fault.Second,nearly S-N extension in Miocene,it caused the intrusion of pale granite,the toughness fault flowed northward,and metamorphic mineral orientation.Third,NE-SW extrusion in later Miocene,a large number of near vertical cleavage zones were developed in the Miocene granite.There are X-shaped joints in sandstone and slate in Ridang Formation and Lure Formation of Jurrassic,and the joints are filled with calcite veins.Forth,NW-SE extrusion in later Miocene,which formed joints and gentle cleavage belts in the Miocene granite.Fifth,NNW-SSE extrusion in later Miocene,which formed shear joints and reverse fault in the Miocene granite.Calcite veins in the X-shaped joints which were formed in the third period were replaced by quartz veins.Sixth,nearly S-N extension in Quaternary,which caused normal faulting of the main brittleness fault and normal fault system in the Miocene granite.Combined with the study of the stress evolution of the Luozha fault and the metallogenic regularity of the deposits in the area,we think that Luozha fault may provide the ore-containing space for mineralization,control the source of mineralization and provide thermal energy for driving the ore-forming fluid circulation.