摘要
黑龙江省黑河地区广泛发育侏罗—白垩纪火山岩,但是该火山岩的岩石组合、成因和所表征的大地构造环境目前有很大的争议。本文对该套火山岩开展详细的岩石学、岩石地球化学等研究。该火山岩形成于早白垩世,主要以安山岩-英安岩-流纹岩为主,包含英安岩、安山岩、粗面岩、流纹岩、安粗岩、玄武安山岩、粗面英安岩、钾玄岩、歪长粗安岩,因此属于弧火山岩的组合。该区火山岩主要为亚碱性系列,岩石Na_2O/K_2O比值一般>1.2。A/CNK在1附近,为准铝质-过铝质岩石。SiO_2-TFeO/MgO图上既有钙碱性系列(包括低铁钙碱性系列),又有拉斑系列。SiO_2-K_2O图上主要为中钾钙碱-高钾钙碱系列。SiO_2-(Na_2O+K_2O-CaO)图上主要为钙碱系列、碱钙系列和碱性系列,在SiO_2-MgO图中主要落入实验玄武岩的局部熔融范围和镁安山岩系列范围。痕量元素蛛网图显示富集大离子亲石元素,K、La、Zr、Hf、Tb、Tm为峰,亏损Nb、Ta、Ti、Y、Yb等高场强元素。稀土元素球粒陨石标准化配分模式为缓右倾型的模式,轻稀土相对富集,重稀土内部分馏不明显,具有微弱负Eu异常。大部分岩石具有高Sr低Y的特征,其中一些岩石具有adakite岩的特征。上述特征均指示弧火山岩的特征。结合构造环境判别认为该火山岩形成于与洋俯冲有关的环境,推测岩浆可能的源区为俯冲的洋壳、上覆的地幔楔、兴安弧的下地壳。
The Mesozoic volcanic rocks are extensively developed in the Heihe area of Heilongjiang Province,but their geological dating,rock assemblage,petrogenesis and tectonic setting remain unclear.This paper focuses on the petrology and geochemistry of volcanic rocks in this area.Our study showed that the volcanic rocks formed in the Early Cretaceous.They comprise mainly of andesite,dacite and rhyolite,but also contain trachyte,latite,basaltic andesite,trachydacite,shoshonite and benmoreite.The rock assemblage therefore is of arc-volcanic rock assemblage.These rocks mostly belong to the sub-alkaline series with Na2O/K2O ratio1.2 in general.The rock assemblage is metaluminous-peraluminous in the A/CNKA/NK diagram.Other rock series of lesser quantity were also shown in the oxide phase diagrams：both calcalkaline（including low Fe calc-alkaline（LF-CA））and tholeiitic（TH）series in SiO2-TFeO/MgO diagram,high-K calc-alkaline and medium-K calc-alcaline series in SiO2-K2O diagram,calc-alkaline/alka-calcline and alkaline（CA＋AC＋A）series in SiO2-（Na2O＋K2O-CaO）diagram,and experimental basaltic and magnesium andesitic melting ranges in SiO2-MgO diagram.The rocks were enriched in LILE（K,La,Zr,Hf,Tb and Tm）and depleted in HFSE（Nb,Ta,Ti,Y and Yb）.They were relatively enriched in LREEs and slightly depleted in HREEs with weak negative Eu anomaly.Most of the rocks had high Sr and low Y contents,some displayed adakite characteristics.Overall,the geochemical characteristics were consistent with arc volcanic rocks and in accordance with the rock assemblage. Taking into account tectonic setting discrimination result,we propose that the volcanic rocks were formed in subducted oceanic zones,and the magma source areas were likely subducted oceanic crust,upper mantle wedge,and lower crust of Xing＇an Arc.
作者
邵帅
邓晋福
刘翠
赵院冬
段培新
许逢明
狄永军
SHAO Shuai;DENG Jinfu;LIU Cui;ZHAO Yuandong;DUAN Peixin;XU Fengming;DI Yongjun(School of Earth Sciences and Resources, China University of Geoscienses （ Beijing ） , Beijing 100083, China;Shenyang Geological Survey, China Geological Survey, Shenyang 110000, China;China Aero Geophysical Survey and Remote Sensing Center for Land and Resources, Beijing 100083, China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2018年第3期215-229,共15页
Earth Science Frontiers
基金
中国地质调查局项目(DD-16-049,12120114055701,12120115069701,12120114020901,中地调研合同[2016]第132号)
国家自然科学基金项目(41502063)
关键词
黑龙江黑河地区
早白垩世
火山岩组合
弧火山岩
俯冲环境
Heihe area in Heilongjiang Province
Early Cretaceous
volcanic rocks assemblage
arc-volcanicrocks
subduetion setting
