Granitoid batholiths: Structuring and processing of information and comparative characteristics

Geological, geophysical, and geochemical materials on Mesozoic granitoids o f the Mongolo-Okhotsk Zone (MOZ) are systematized and structured. A databas e (DB) on 947 granitoid massifs of the MOZ is compiled; 332 of the massifs (including 50 granitoid batholiths) are described in detail. Similar inform ation is prepared for granitoid batholiths of other regions (Kuznetsk Alata u, East Sayan). Results of processing of the database information are given . Geophysical data on the arrangement and areas of exposure of granitoids i n the MOZ and in the entire Earth's crust evidence that they form batholith s at least 300 km(2) in size. A correlation was made between the geochemica l zonation of Mesozoic granitoid magmatism and the structure and thickness of the lithosphere in the MOZ. It is shown that alkali and subalkalic grani toids are predominant in the areas with thick continental lithosphere and g ranitoids of normal alkalinity - in the areas with thinner lithosphere. Thi s model does not rule out participation of mantle-derived fluids in the mag ma formation. The level of alkalinity (normal, subalkalic, and alkaline) an d the type of alkalinity (potassic, sodic, and potassic-sodic) of granitoid s are magmatic criteria determining a difference of lithospheric blocks in maturity, thickness, crust-mantle proportion, etc. The diversity of the geo chemical types of granitoids is caused by changes in alkalinity and composi tion of juvenile fluid, which is manifested in the existence of specific ma gmatic associations (syenite-alaskite and granodiorite-granite series), and by different compositions of protoliths and mechanisms of granite formatio n (palingenetic rare-metal models). The distribution of the geochemical typ es of granitoids from various facies is close to the Gauss curve, which, al ong with the regularities of their areal arrangement, evidences that the gr anitoids are self-organized systems and that the above geochemical typizati on is correct. By the example of model granitoid batholiths, it is shown th at element distribution in granitoids of a metabasic crustal substratum is similar to that in the middle-lower crust, whereas the geochemical composit ion of granitoids of diorite-granodiorite substratum is close to that of th e upper crust.