Mesozoic Magmatism Time Limit Of The South Taihang And Its Tectonic Significance

The South Taihang Mountains is located in the southern section of the Mesozoic Taihang Mountains Intraplate Orogenic Belt,in the middle of the North China Craton,and experienced a strong magma-tectonic effect in the Mesozoic.Large-scale intense magmatism is an important indicator of the destruction of the North China Craton.The spatio-temporal characteristics of the magmatic activity record the process of the destruction of the North China Craton,which provides an excellent target for us to study the mechanism of the craton destruction.This paper systematically collects the chronological and geochemical data of the Mesozoic magmatic rocks in the South Taihang Mountains region,and establishes a corresponding database.Based on this,through field investigation,petrographic studies of typical lithological samples,zircon dating and geochemical analysis has improved the database of Mesozoic intrusive rocks in this region,constructed a time-space framework for the Mesozoic magmatism of the South Taihang Mountains,and traced the rhythm and evolution law of the Mesozoic magmatism,providing a discussion on the time limit and destruction mechanism of the North China Craton.The Mesozoic magmatic rocks of the South Taihang Mountains can be divided into the western,central and eastern magma belts according to the space.The overall lithology is dominated by the intermediate and basic rocks.The zircon LA-ICP MS U-Pb dating results indicate that the emplacement age of the western magma zone in ranged from 141 to 119 Ma with a peak period of 129 to 127 Ma.The emplacement age of the central magma belt is144 ? 119 Ma,the peak period is 131 ? 129 Ma,and the emplacement age of the eastern magma belt is 142 ? 120 Ma,and the peak period is 132 ? 130 Ma.Through petrographic studies,geochemical analysis and zircon in-situ Lu-Hf isotope analysisis,it is known that the Mesozoic magmatic rocks of the South Taihang Moutains originate from the enriched mantle.The Fushan intrusion formed by follow process: the basic magma originating from the lithospheric mantle(EM1)and invades into the lower part of the crust and causes the lower crust partially melting and form acidic magma.Both of them undergo a similar MASH process at the crust-mantle boundary,and formed a dioritic magma chamber in the deep crust(15-17km),experienced the crystallization process of amphibole-dominated in the magma chamber,the mantle-derived magma injected into the magma chamber multiple times,and the evolved magma pulsated into the shallow part of the crust(1-5km).The Kuangshan intrusion is formed by mixing of basic magma derived from the lithospheric enrichment mantle(EM1)and acidic magma originated from the lower crust,and undergoes crystallization differentiation process.The Hongshan intrusion formed by follow process: the upward emplacement of the(EM1)basic magma originating from the enriched mantle mixed with a small amount of crustal material,and undergoes two-stage separation and crystallization.Combined with the tectonic setting of the region where the South Taihang is located at,this paper considers that the Mesozoic magmatic rocks of the South Taihang Mountains are formed in the post-collision environment.Due to the change in the subduction angle of the Western Pacific Plate and the East Asian continent,a stagnant plate was formed during the trench retracement and plate reversal.Dehydration of the retained plate leads to unsteady turbulent flow.Under this background,the deep fluid migrates to the lithospheric mantle,leading to the melting of the enrichment mantle and forming basic magma.Acitic mgama is produced by melting of lower crust.In different deepth,basic magma mixed with the acidic magma.