扬子西缘小相岭地区苏雄组古火山机构的发现及意义
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摘要
通过详细的野外地质调查,发现扬子西缘小相岭地区苏雄组火山岩由巨厚的酸性-中酸性熔岩、火山碎屑岩和少量基性熔岩组成,在小相岭山脊两侧首次厘定4处古火山机构。其中,阳糯雪山古火山机构最壮观,是由火山颈相、溢流相、爆发相和火山沉积相构成的完整古火山机构。通过系统的地质剖面研究,发现该古火山机构存在2次喷发亚旋回和15个火山韵律,2次喷发亚旋回之间出现了1次明显的火山间歇期。小相岭地区古火山机构的发现,进一步厘定了苏雄组火山岩的喷发方式和构建特征,对进一步研究苏雄组酸性火山碎屑岩的起源及新元古代陆内裂谷作用具有重要意义。
The detailed geological survey shows that Suxiong Formation in Xiaoxiangling area of western Yangtze Block, consists of thick acid-intermediate acid lavas, volcaniclastic rocks and a small amount of basic lavas. And for the first time, four ancient volcanic apparatuses were found on both sides of the ridge of Xiaoxiangling Mountain. The volcanic apparatus in Yangnuo Snow mountain is the most grand, typical and complete sight and consists of volcanic neck facies, effusive facies, explosive facies and volcanic sedimentary facies. Systematic study of geological profile revealed that there were two eruption cycles, including fifteen volcanic rhythms, and there was a distinct period of volcanic intermission between these two eruption cycles. The discovery of these ancient volcanic apparatuses in Xiaoxiangling area can be used for further determination of volcanic eruption pattern and construction feature of Suxiong Formation. And this discovery can be also of significant importance to the study of the source of acidic volcanic rocks of Suxiong Formation and intracontinental riftimg in Neoproterozoic Era.
The detailed geological survey shows that Suxiong Formation in Xiaoxiangling area of western Yangtze Block, consists of thick acid-intermediate acid lavas, volcaniclastic rocks and a small amount of basic lavas. And for the first time, four ancient volcanic apparatuses were found on both sides of the ridge of Xiaoxiangling Mountain. The volcanic apparatus in Yangnuo Snow mountain is the most grand, typical and complete sight and consists of volcanic neck facies, effusive facies, explosive facies and volcanic sedimentary facies. Systematic study of geological profile revealed that there were two eruption cycles, including fifteen volcanic rhythms, and there was a distinct period of volcanic intermission between these two eruption cycles. The discovery of these ancient volcanic apparatuses in Xiaoxiangling area can be used for further determination of volcanic eruption pattern and construction feature of Suxiong Formation. And this discovery can be also of significant importance to the study of the source of acidic volcanic rocks of Suxiong Formation and intracontinental riftimg in Neoproterozoic Era.
引文
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[20] 陈宁,王炬川,杨涛,等.西昆仑上其汗地区火山岩LA-ICP-MS锆石U-Pb年龄及构造意义[J].中国地质调查,2016,3(3):21-28.
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[2] Zhao J H,Zhou M F,Yan D P,et al.Zircon Lu-Hf isotopic constraints on Neoproterozoic subduction-related crustal growth along the western margin of the Yangtze Block,South China[J].Precambr Res,2008,163(3/4):189-209.
[3] Huang X L,Xu Y G,Lan J B,et al.Neoproterozoic adakitic rocks from Mopanshan in the western Yangtze Craton:Partial melts of a thickened lower crust[J].Lithos,2009,112(3/4):367-381.
[4] 任光明,庞维华,孙志明,等.扬子西缘会理地区通安组角闪岩锆石U-Pb定年及其地质意义[J].矿物岩石,2014,34(2):33-39.
[5] 郭建强,游再平,杨军,等.川西石棉地区田湾与扁路岗岩体的锆石U-Pb定年[J].矿物岩石,1998,18(1):92-95.
[6] Sun W H,Zhou M F,Yan D P,et al.Provenance and tectonic setting of the Neoproterozoic Yanbian Group,western Yangtze Block(SW China)[J].Precambr Res,2008,167(1/2):213-236.
[7] Du L L,Guo J H,Nutman A P,et al.Implications for Rodinia reconstructions for the initiation of Neoproterozoic subduction at～860 Ma on the western margin of the Yangtze Block:Evidence from the Guandaoshan Pluton[J].Lithos,2014,196/197:67-82.
[8] 张盛师.四川西南部苏雄组及其相当地层的时代和划分对比[J].四川地质学报,1985:114-124.
[9] 马国干,张自超,李华芹,等.扬子地台震旦系同位素年代地层学的研究[G]//中国地质科学院宜昌地质矿产研究所文集.1989:83-124.
[10] 李献华,周汉文,李正祥,等.扬子块体西缘新元古代双峰式火山岩的锆石U-Pb年龄和岩石化学特征[J].地球化学,2001,30(4):315-322.
[11] 卓皆文,江新胜,王剑,等.川西新元古界开建桥组底部沉凝灰岩锆石SHRIMP U-Pb年龄及其地质意义[J].矿物岩石,2015,35(1):91-99.
[12] 李献华,周汉文,李正祥,等.川西新元古代双峰式火山岩成因的微量元素和Sm-Nd同位素制约及其大地构造意义[J].地质科学,2002,37(3):264-276.
[13] Li Z X,Li X H,Kinny P D,et al.Geochronology of Neoproterozoic syn-rift magmatism in the Yangtze Craton,South China and correlations with other continents:Evidence for a mantle superplume that broke up Rodinia[J].Precambr Res,2003,122(1/2/3/4):85-109.
[14] 李献华,祁昌实,刘颖,等.扬子块体西缘新元古代双峰式火山岩成因:Hf同位素和Fe/Mn新制约[J].科学通报,2005,50(19):2155-2160.
[15] 刘鸿允.中国晚前寒武纪构造、古地理与沉积演化[J].地质科学,1991(4):309-316.
[16] 四川省地质局第一区测队.四川1∶20万冕宁幅区域地质调查报告[R].1967.
[17] 四川省地质矿产勘查开发局.四川省岩石地层[M].武汉:中国地质大学出版社,1997.
[18] Huang X L,Xu Y G,Li X H,et al.Petrogenesis and tectonic implications of Neoproterozoic,highly fractionated A-type granites from Mianning,South China[J].Precambr Res,2008,165(3/4):190-204.
[19] 朱玉书.川西小相岭早震旦世火山岩地层划分及喷发环境的探讨[J].地层学杂志,1982,6(2):101-106.
[20] 陈宁,王炬川,杨涛,等.西昆仑上其汗地区火山岩LA-ICP-MS锆石U-Pb年龄及构造意义[J].中国地质调查,2016,3(3):21-28.
[21] 张照伟,李文渊,张江伟,等.新疆北部晚古生代大规模岩浆作用与成矿耦合关系研究主要进展及成果[J].中国地质调查,2015,2(6):20-25.
[22] Martí J,Groppelli G,Da Silveira A B.Volcanic stratigraphy:A review[J].J Volcanol Geotherm Res,2018,357:68-91.
[23] 董榕生,李建林.川西甘洛苏雄早震旦世地层及其火山岩系特征[J].成都地质学院学报,1979(2):1-19.
[24] 殷继成,丁莲芳,何廷贵,等.四川峨眉—甘洛地区震旦纪地层古生物及沉积环境[M].成都:四川人民出版社,1980.
[25] 马国干,李华芹,张自超.华南地区震旦纪时限范围的研究[G]//中国地质科学院宜昌地质矿产研究所文集.1984:1-29.