摘要
新疆富蕴县五彩城岩体出露于卡拉麦里断裂以南,呈北西-南东向的带状分布,侵位于下石炭统松喀尔苏组,LAICPMS锆石U-Pb年龄显示,该岩体形成于早石炭世(206Pb/238U的加权平均年龄为341.1±4.0Ma和340.9±5.1Ma)。岩石组合为二长花岗岩+钾长花岗岩,闪长质包体发育。岩石低Si O2(59.35%~69.51%),Na2O>K2O,A/CNK<1.1,SiO2与P2O5具有较好的负相关性,暗色矿物主要为角闪石,显示出I型花岗岩的特点。岩体富集大离子亲石元素(K、Rb和Ba),不同程度的亏损Nb、Ta、P和Ti、ΣREE较高(126.0×10-6~172.7×10-6),δEu不明显(0.75~0.95),与西准噶尔地区早石炭世后碰撞花岗岩的特点相似。花岗岩具有正的εNd值(+5.4^+5.5)、较低的Isr值(0.70289~0.70335)及年轻的Nd模式年龄(tDM1=650Ma、tDM2=650~680Ma),表明花岗岩来源于年轻地壳。岩石地球化学显示,该岩体形成于后碰撞环境,与黄羊山、老鸭泉(卡拉麦里断裂以北)等地的晚石炭世A型花岗岩的构造属性一致。五彩城I型花岗岩的锆石年龄代表了卡拉麦里地区后碰撞花岗岩的最老年龄,表明卡拉麦里有限洋盆在早石炭世中期之前(晚泥盆世?)已经闭合。
Wucaicheng pluton is located in the south of Karamaili in Fuyun County in Xinjiang,which shows a characteristic of zonal distribution from NW-SE and is intruded in Songkaersu Group of the Lower Carboniferous,LA-ICPMS zircon U-Pb age shows that the pluton＇s206Pb /238 U ages are 341. 1 ± 4. 0Ma and 340. 9 ± 5. 1Ma. The rock associations of Wucaicheng pluton are monzogranite and K-feldspar granite,the dioritic enclaves are universal,the characteristics of I-type granites is mainly displayed that low Si O2content（ 59. 35% ～ 69. 51%）,Na2 O 〉K2 O,A / CNK 〈1. 1,a good negative correlation between Si O2 and P2O5,the amphibole being main dark mineral. The geochemical characteristics of the pluton shows enrichment in LILE（ K,Rb,Ba）,depletion in Nb,Ta,P and Ti,relatively high REE contents and negligible Eu anomalies（ 0. 75 ～ 0. 95）,which is similar with Early Carboniferous postcollisional granites in western Junngar. Granites are characterized by positive εNd（ t） values（ ＋ 5. 4 ～ ＋ 5. 5）,a relative low initial Sr isotopic ratios（ ISr= 0. 70289 ～ 0. 70335） and young Nd model ages（ tDM1= 650 Ma,tDM2= 650 ～ 680Ma）,so the possible magma source could be the young crust. The petrological and geochemical characteristics indicate that Wucaicheng pluton belongs to postcollisional granites which include Late Carboniferous granites in the north of Karamaili fault（ Huangyangshan and Laoyaquan,etc.）.The zircon U-Pb age of Wucaicheng I-type granites in this paper is the eldest age of post-collisional granites in Karamaili,which manifests that the ocean basin of Karamaili has been closed before the middle stage of Early Carboniferous（ Late Devonian？）.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第5期1471-1484,共14页
Acta Petrologica Sinica
基金
中国地质调查局计划项目(1212011120508)资助
关键词
卡拉麦里
五彩城
I型花岗岩
后碰撞
东准噶尔
Karamaili Wucaicheng I-type granites Post-collision Eastern Junngar
