内蒙古渣尔泰地区中生代火山岩地球化学特征及构造环境分析
发布时间：2019-05-28 10:58
【摘要】：内蒙古渣尔泰地区处于华北地台西北部,其分布的中生代火山岩划分为两大类,形成于两个喷发旋回。早白垩世早期喷发旋回以中基性火山岩为主,沿近东西向的深大断裂呈北东东向裂隙式喷发;晚期喷发旋回以酸性火山岩为主,沿近南北向断裂带呈裂隙-中心式喷发。中基性火山岩主要为橄榄玄武粗安岩和安粗岩,其SiO_2介于49.65%~56.64%;酸性火山岩包括次火山岩、火山碎屑岩、火山熔岩,其Si O2介于73.18%~83.82%;两者组成典型的宽双峰火山岩。中基性火山岩富碱(Na_2O+K_2O=6.70%~7.47%)、高Ti(TiO_2=2.29%~3.55%)、Fe,相对贫Ca、Mg,富含大离子亲石元素(LILE)(Rb、Ba),轻稀土相对富集,轻、重稀土元素分馏明显,LREE/HREE=4.50~6.47,(La/Yb)N=4.17~8.85,具微弱的负Eu异常(δEu=0.67~0.96),具有与洋岛玄武岩(OIB)相似的地球化学特征,其岩浆来源于交代富集的软流圈地幔,岩浆上升过程中地壳组分混染较少。酸性火山岩富Si、高K,贫Ca、Mg、Fe、Ti,富含大离子亲石元素(LILE)(Rb、Th、U)和高场强元素(HFSE)(Nb、Ta、Zr、Hf),富集轻稀土,LREE/HREE=2.91~14.3,轻、重稀土分馏明显,(La/Yb)N=2.53~28.4,(La/Sm)N=1.16~4.57,(Gd/Yb)N=1.22~5.04,负Eu异常明显(δEu=0.02~0.25),具有A型流纹岩的特征,为幔源岩浆底侵,使上覆的先存地壳岩石发生部分熔融的产物。结合区域地质背景,认为研究区双峰式火山岩形成于西伯利亚板块与华北板块碰撞造山期后陆内拉张的构造环境。
[Abstract]:The area of Jiltai, Inner Mongolia, is located in the northwest of the North China platform. The Mesozoic volcanic rocks are divided into two types, which are formed in two eruptive cycles. In the early Cretaceous, the middle basic volcanic rocks were the main eruptive cycles, and the deep faults along the near east-west direction were in the north-east-west fracture type, while the late eruption cycles were mainly acidic volcanic rocks, and the near-north-south fault zones were fissured-central eruptions. The middle basic volcanic rocks are mainly olivine-Black Tortoise trachyandesite and their SiO_2 is between 49.65% and 56.64%, while acidic volcanic rocks include subvolcanic rocks, pyroclastic rocks and volcanic lava, and their Si O2 is 73.18% and 83.82%, respectively. The two constitute typical wide bimodal volcanic rocks. The middle basic volcanic rocks are alkali-rich (Na_2O K 鈮，
本文编号：2486994
[Abstract]:The area of Jiltai, Inner Mongolia, is located in the northwest of the North China platform. The Mesozoic volcanic rocks are divided into two types, which are formed in two eruptive cycles. In the early Cretaceous, the middle basic volcanic rocks were the main eruptive cycles, and the deep faults along the near east-west direction were in the north-east-west fracture type, while the late eruption cycles were mainly acidic volcanic rocks, and the near-north-south fault zones were fissured-central eruptions. The middle basic volcanic rocks are mainly olivine-Black Tortoise trachyandesite and their SiO_2 is between 49.65% and 56.64%, while acidic volcanic rocks include subvolcanic rocks, pyroclastic rocks and volcanic lava, and their Si O2 is 73.18% and 83.82%, respectively. The two constitute typical wide bimodal volcanic rocks. The middle basic volcanic rocks are alkali-rich (Na_2O K 鈮，
本文编号：2486994
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