The Evolution Of The Crystalline Rock Series In Taili, Xingcheng, Liaoning Province

The Xingcheng Taili area situated at the north of the North China platform and the east of the YanShan belt of folded strata. It exposes the Precambrian and orogen crystalline rocks including biotite hornblende plagioclase gneiss,granitic gneiss in Archean, biotite Monzonitic granite (light-colored granite),augen granitic gneiss in Mesozoic, dike rocks like grant granite,garnet granite and basic dike rocks. The Archean rocks experienced multiple periods varying degrees of deformation-metamorphism, magmatism, so that the original rock's appearance and continuity were broken and reconstructed.This article introduced briefly the regional geology background of the Xingcheng Taili crystalline rocks , including the regional geology survey,the regional tectonic,lithostratigraphic units, discussed the characteristic of geology,geochemistry,isotope chronology and granite's metamorphic warm-pressing, talked the crystalline formation age,tectonic background and invasive manner, and also analyzed of the different rocks in magma stadium invasion time and the deterioration-distortion order in detail.The research discovered that the area in Xingcheng Taili exposed crystalline rocks is not only the abyssal rocks which intruded in Precambrian, but also the intrusion in Mesozoic era. Meanwhile, we have confirmed above from the study of the LA-ICP-MS zircon U-Pb ages. We consider preliminarily according to the isotope ages that the gneissic granite original magma intrusion age is about 2522Ma, and subjected to several metamorphism; the augen granitic mylonite original magma emplacement age is about 216.58Ma in the Late Triassic, and was controlled by Indo-China movement; and the biotite monzonitic granite's original magma emplacement age is about 152Ma in Mesozoic.In addition, we have identified the rock geochemistry, petrogenesis and tectonic environment by geochemical analysis including the major elements, trace elements and rare earth elements. We finds that the biotite hornblende plagioclase gneiss which belongs to the trachy-andesite and partial calc-alkaline series in Taili, has a homology with the plagioclase amphibolite as a inclusion in the granite gneiss and the biotite plagioclase gneiss as a inclusion in the bleached granite, and indicates a character of different tiation; the granite gneiss belongs to the granite and calc-alkaline series, whose tectonic background shows the postorogenic granite, and also indicates the character of different tiation; And the bleached granite is a granite, calc - alkaline rocks, it belongs to the partial aluminum rock according to the A/CNK, the same tectonic background for the postorogenic granite. As to the vein rocks in study area, the augen gneiss granite for the granitic, calc - alkaline rocks, the higher REE, LREE enrichment compared to the granite formation of granite, has a good balance characteristics of partial melting; the grant granite belongs to K calc - alkaline rocks, whose original rock may be recrystallizated and replaced by the lava from the deep crust, and its tectonic background shows the postorogenic granite; and the Garnet granite has a strong fractional crystallization in the process of intrusion, whose tectonic setting also showed the postorogenic granite and the mantle-type granite.This study uses the latest geothermobarometers- ternary feldspar geothermobarometersin the study of volcanic rocks of granite in particular to assay the temperature and pressure of some rocks in the study area for the first time to judge their crystallization's temperature and pressure. Among them, the biotite monzonitic granite of high P/T (high-pressure type)<20°C/Km shows that it is a high-temperature gradient, and intruded about 33Km at the underside of the crust as a pressure for 11.2 Kbar, and the crystalline temperature of the feldspar was 637.95°C. According to the characteristics of rocks, Mineral balance and the choice of temperature and pressure measured, the augen gneiss granite in some areas suffer a strong mylonite, and the pressure and temperature of the metamorphic rock deformation should be, 646.93°C ,the temperature gradient was between 20°C/Km~40°C/Km, 23 Km equivalent to the crust, rock by a strong regional power ductile deformation, as the temperature decreases, feldspar the crystallization temperature of 646.93℃,and intruded about 23Km at the underside of the crust as a pressure for 7.84Kbar, and the crystalline temperature of the feldspar was 637.95°C.