Geochemical Characteristics And Genetic Analysis Of Quartz Monzotite Porphyry In The Southern Part Of Taihang Mountains

The Motianling area in the southern Taihang Mountains is located in the northern part of Zhongtiaoshan in the southern margin of the craton in the central part of the North China Platform,with the Zanhuang uplift in the East and Jingxing depression in the west.There are many rock mass in the Central Orogenic Belt of Taihang Mountains.Among them,quartz monzonitic porphyry intrusions mostly that have small rock bodies and dikes are well developed,which occur in Shipozui,Huaishuzhuang and Mengjiaping.1.The quartz feldspathic porphyry in the study area is in the form of a vein with a pulse width of 7¹0m,which intrudes into the strata of nansizhang formation of gantahe group in motianling and cuts fine sandstone of the second section of nansizhang formation.2.U-Pb of quartz monzotite zircon from the motianling area in the southern part of taihang mountain was 2118±45Ma old and formed in the middle proterozoic era.3.Geochemical characteristics showed that the SiO₂ content of the sample was71.1%⁷7.4%,the Al₂O₃ content was 11.75%¹5.3%,belongs to peraluminum,the A/CNK ratio was 1.74².78,the total alkali content was 5.02%⁶.03%,and the Na₂O/K₂O content was 1.42⁶.87.The alkalinity rate?AR?was 1.95².52,which was calc-alkaline,and the consolidation index was 11.15,indicating a high degree of magma differentiation.The distribution of rare earth elements is right-leaning,and the large ion lipophilic elements such as Rb,Ba and K are enriched,while the high field intensity elements such as Ta,Nb,Sr,P and Ti are lost.The total amount of rare earth elements is 63.44×10^-6129.66×10^-6,and the ratio of light to light rare earth elements is more than 10,showing obvious differentiation.LREE relative enrichment,HREE relative loss,Eu and Ce anomalies are not obvious.It is concluded that quartz monzophyre is a highly differentiated peraluminous calc-alkaline type I granite.4.Quartz monzophyre is volcanic arc granite,which is the product of partial melting of the lower crust.The magmatic source area originates from the lower crust of the low-pressure environment,and the tectonic environment is a subduction type tectonic environment related to arc,which indicates that the formation of crystalline basement of the north China craton should be delayed to 2118Ma at least.