河南泌阳县陈庄-马谷田一带桃园岩体形成构造环境:岩石地球化学及锆石年代学证据

Genesis of Taoyuan intrusion in Chenzhuang-Magutian area, Biyang County, Henan Province:evidence from geochemistry and zircon U-Pb geochronology

分布在泌阳县陈庄-马谷田一带的桃园岩体岩性主要为英云闪长岩、奥长花岗岩、花岗闪长岩,属于TTG岩石组合。岩相学、岩石地球化学研究表明,桃园岩体为低钾钙碱性系列,轻稀土元素富集,明显负铕异常,总体亏损高场强元素和重稀土元素,岩浆来源于地壳物质的部分熔融。桃园岩体锆石(LA-ICP-MS)206Pb/238U加权平均年龄在423.2±2.9 Ma^445.3±1.7 Ma之间,即桃园岩体形成于早志留世。早古生代北秦岭微陆块向北俯冲过程中,在岛弧岩浆岩带靠近海沟一侧俯冲板片部分熔融形成了桃园岩体,属于不成熟岛弧环境下的产物。

Taoyuan intrusion is mainly composed of the diorite, orogranite and granite, and also belongs to the tonalite-trondhjemite-granodiorite（TTG） suite, which located in Chenzhuang-Magutian area, Bixian County, Henan Province. Through the research of the petrography, the lithogeochemistry and the zircon U-Pb geochronology,Taoyuan intrusion have the following characteristics： it＇s belongs to lowpotassium calcium alkalinity series, enrich in LREE, depleted in HREE and HFSE, specially apparent negative anomaly of Eu, which shows that the magma of Taoyuan intrusion come from the partial melting of crustal material. The weighted average zircon206Pb/238 U ages of Taoyuan rocks are between 423.2±2.9 Ma and 445.3±1.7 Ma, which represents the formation age of the rock, and belongs to the early Silurian. At the period of early Paleozoic, North Qinling Micro-Plate subducted to the north, and the subduction ocean plate melted into forming the Taoyuan intrusion at the side of the island-arc rocks closing to the trench, which showthat it is the product of an immature island arc.