South Qinling Ziyang - Zhenba regional mafic intrusions and geological significance of the dynamic mechanism discussed

Title: South Qinling Ziyang - Zhenba regional mafic intrusions and geological significance of the dynamic mechanism discussed
　　Author: Zhang Xin
　　Degree-granting units: Chang'an University
　　Keywords: South Qinling;; early Paleozoic;; basic intrusive body;; rift environment;; rock geochemistry
　　Summary:
　　Choose paper Ziyang, Shaanxi - Zhenba region in the early Paleozoic strata exposed in the base for the study of intrusion by intrusion of these mafic petrology, geochemistry, geochronology and other systematic study of its causes and source characteristics, in order to bound the area of ​​tectonic setting.
　　Ziyang - Zhenba in the development of Early Neodymium Magnets Paleozoic strata lot, the NE - SW trending mafic intrusions, which show the direction of regional stratigraphic distribution close to the same direction, along the visible intrusion into the relationship; these mafic intrusions main rock types: diabase, gabbro-diabase, gabbro, diabase porphyrite. On the light gray in - for fine-grained gabbro zircon U-Pb (LA-ICPMS) isotopic dating results show that the magmatic activity occurred in the Early Silurian (437.7 ± 2.3Ma), its formation age basalts with Langao the same class and trachyte, together constitute a bimodal volcanic rock, indicating the area in the late Paleozoic crust in an extensional extensional event.
　　Whole-rock mafic intrusions of major and trace element analysis results show that the intrusion in this area between the SiO2 content of 40.14% -55.98% change between, on the whole Si02 content is relatively low, the base of the main. Na2O, TiO2 content, K2O content is slightly lower, the main as the alkaline series, characterized by extension of the period of the early stages of the event for the rift. More enriched in LREE, with a slightly positive Eu anomaly. Chondrite-normalized REE patterns are composed of smooth right-wing type, Ce negative anomaly, a variety of environmental discrimination diagram shows the characteristics of intra-plate tectonic setting, rare earth, trace element characteristics show mafic intrusions and continental rift basalt characteristics similar to the area was Ti-rich mafic and loss P, Sr, and southwest China that feature the Late Permian Emeishan mantle plume head melting and the formation of high-Ti basalts is similar to other intrusions Ta / Hf ratios of between 0.34-0.56 , the reaction of mafic intrusions in the area have similar oceanic island basalt asthenosphere causes mantle-derived magma characteristics.
　　Sr-Nd isotopic study of mafic intrusions in the area that the magma source is a major from the EMII end-as the main component, and a small amount of HIMU and EMI components join end-enriched mantle source, and has a and OIB mantle source similar characteristics. Mafic intrusions in the study area from the lithospheric mantle, the original magma rising http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets process may be accompanied by crustal material contamination, and, lithospheric mantle is constrained nature of the most important source of magma. Nb/Ba-87Sr/86Sr correlation diagram suggests that the magma source region has been enriched lithospheric mantle affected.
　　Articles by Ziyang in Shaanxi - the Early Paleozoic intrusions Zhenba systematic study, revealed in the late Paleozoic, the northern margin of Yangtze Plate region of South Qinling stretching a crustal extension event, with the Qinling orogenic Caledonian movement by cracking pull the event closely related, and with oceanic island basalt asthenosphere similar upwelling of mantle-derived magma, and cause the heat of the overlying strata - mechanical erosion also has a certain relationship between the Qinling orogenic belt in the Paleozoic tectonic evolution has an important significance.
　　Degree Year: 2010