Emplacement Mechanism Of Yuechengling Granitic Pluton, Northeast Guangxi

In this paper, based on a comprehensive summary of previous data and research results,the geological survey of a lot of Yuechengling granite body and surrounding rock, makingfull use of the research methods of petrology, geochemistry, geochronology, magnetic fabric,this paper determined basically the emplacement mechanism of Yuechengling granite andmade the following main results or understanding.Firstly, Using the technology ofLAM－ICPMS zircon U-Pb to determine the age ofYuechengling granite.The results show that the age of Yuechengling granite is437±12Ma、432±9.5Ma、404±9.5Ma.Secondly, According to YueChengLing isotope age, rock type and geologicalcharacteristics of granite rock mass，established five sequences：Luojiang，Nandong，Daxijiang，Xinning，Daniaojie, and one independent unit Xiangtangli.Thirdly, Yuechengling granite rock magnetic fabric characteristics show that: the rockmass is based on flaser ellipsoid and mostly on the intrusive body side, reflect the extrusionenvironment. few rocks are elongated ellipsoid, proximity to the intrusive body, reflects thetensile environment. The degree of the magnetic anisotropy in the Caledonian granite,generally the trend is weakening from the intrusive body center to the edge.Rock aciditygradually enhanced, and with the increase of content of SiO2, Al2O3, CaO, FeO, MgO style,P2O5content increased gradually, Na2O+K2O content gradually decreased;Rb/Sr ratio2.07,24.19,0.57, the Rb/Ba ratio of0.33,0.67,6.00, are gradually increased and the changeis bigger, that magmatic evolution experienced a high degree of differentiation;Delta the Eufrom1.35-0.82-0.10, each unit granite samples type standardization of rare earth elementdistribution curve for the enrichment of light rare earth type both right model, shows thatthey have a certain similarity and continuity in origin.fourthly, to YueChengLing granite rock mass and the structure characteristics ofsurrounding rock studies have shown that YueChengLing granite flat oval, intrusion inYueChengLing duplex anticline and its core collapse space occupied, put first regionalstructure has been adjusted to almost the same with the rock mass structure, its contact zoneof the surrounding rock mass, and roughly parallel to the axis direction of rock mass.fifthly, Studies of magnetic fabric features of YueChengLing granitic pluton haveshown that: stage of caledonian and indosinian granitic pluton general is given priority towith the type of flattened ellipsoid，which reflect the extrusion environment and indicatactive emplacement characteristics. Yanshanian granitic pluton is the type of elongatedellipsoid, which reflect tensile environment and indicat the passive emplacement characteristics.In stage of caledonian granitic pluton, the relatively high P values are Mostlydistributed in the edge of the pluton, and with the decresed trend that date from the side ofpluton to the center. The above illustrate that the edge of pluton under bigger stress withsome extrusion strength when the granitic pluton emplacementing and shows thecharacteristics of active emplacement. direction of magnetic lineation of magnetic foliationstage caledonian and indosinian granitic pluton and shows a basic has the same pattern: thedistribution of magnetic foliation direction roughly coordinated with an extension of thegranitic pluton boundary direction, but the Angle from the center to the edge of the graniticpluton changes significantly;The borders of the rock magnetic line direction roughly parallelto the granitic pluton boundary, are nearly NS-trending or south to west, dip slower; Locatedin the inside of the granitic pluton is characterized by east-west and steep angle. This featureshows that after the invasion of magma, first the space occupying nearly east-westhorizontal flow, then gradually becomes nearly ns-trending or south-west lateral extrusionbroaden the space of surrounding rock,which indicates the characteristics of isomorphismfornix role.Sixthly, determine the Yuechengling granitic pluton emplacement tectonic environment,in the Caledonian tectonic environment developed from Volcano arc tectonicenvironment�'the same tectonic environment�'tectonic setting of post collision, andassumes tectonic setting of post collision during the dosinian period and Yanshan period, theYuechengling granites emplaced in tectonic environment of the extrusion effect changedfrom strong to weak, stretch from weak to strong.Seventhly,the comprehensive study shows that the dual characteristics of Yuechenglinggranites are active emplacement and both passive emplacement mechanism. Among them,Caledonian granitic pluton are composite emplacement mechanism of based on the balloonwith dome emplacement mechanism, supplemented by expanding the emplacementmechanism.Indosinian granitic pluton based on the dome emplacement mechanism, thelocal dikes are extended emplacement mechanism. Yanshan period granitic pluton isextended dike emplacement mechanism.