摘要
川藏铁路高速交通廊道研究区地质构造环境较为脆弱,尤其是金沙江结合带、澜沧江结合带、怒江结合带及雅鲁藏布江结合带4条主要的块碰撞结合带,表现出不同程度的活动性。本文在地质建造-构造特征、地震、深部地球物理及活动性等问题的基础上,采用微剂量测氡地球化学手段,实测获取氡异常值及本底值。通过统计分析探讨结合带建造-构造特征、活动性等因素与氯气异常的关系。研究结果表明:自南西至北东,结合带氡气浓度值逐渐升高,反映构造应力水平逐渐降低,活动性呈逐渐升高的趋势。处于江达—德钦岩浆岩带的金沙江结合带及处于岗底斯—腾冲岩浆岩带的嘉黎断裂,放射性本底值最高,反映地壳岩石建造的放射性水平对氡气浓度值影响较大。异常系数s(m_(max)/m_0)与断裂发育规模及其活动性强度有着直接的关联,活动性较强的雅鲁藏布结合带和怒江结合带异常系数均呈较高数值。
The geotectonic environment of Sichuan-Tibet railway is so fragile especially in Jinshajiang suture zone,Lancangjiang suture zone and Bangong Co-Nujiang junction zone which show different activities in the past geological ages.Based on the geological construction-structure features,earthquake,deep geophysics and activity,the radon anomaly value and the background value are obtained by means of radon measurement with micro-dose.The relationship between the characteristics of construction and structure,activity and radon anomaly was discussed by statistical analysis.Results have shown:from southwest to northeast,the concentration of radon increased gradually,reflecting the gradual decrease of tectonic stress level and the increasing trend of activity.The Jinshajiang belt in the Jinda-Deqin magmatic belt and the Jiali fault in the GangdeseTengchong magmatic rock belt have the highest radioactive background value,which reflects that the radioactivity level of crustal rocks has a great influence on radon concentration.The anomalous coefficient s(m_(max)/m_0)is directly related to the scale of fault development and its activity intensity.The anomalous coefficient of the Yarlung Zangbo Belt and the Nujiang Belt are high in the region with strong activity.
引文
[1]谷懿,葛良全,王广西,等.汶川地震震后大成都地区断裂带活动性氡气测量分析评价[J].工程地质学报,2009,17(3):296-300.GU Y,CE L,WANG G,etc.Analysis and evaluation of faults activities in Chengdu region with radon concentration measurements after wenchuan earthquake[J].Journal of Engineering Geology.2010,37(4):107-110.
[2]宋健,唐方头,邓志辉,等.青藏高原嘉黎断裂晚第四纪运动特征[J].北京大学学报(自然科学版),2013,49(6)973-980.Song J.Tang F T.DENG Z H,etc.Later quaternary movement characteristics of Jiali fault in Tibetan plateau[J].ASNUP,2013,49(6)973-980.
[3]徐强,赵俊猛,崔仲雄.等.青藏高原班公湖-怒江缝合带中部的Moho错断[J].科学通报,2010,55(1)80-86.XU Q,ZHAO J,CUN Z X,etc.The Moho plane of Bangong CO-Nuijang in Tibet[J].Science China Press.2010,55(1)80-86.
[4]金胜.青藏高原的壳幔电性结构特征及其动力学意义[D].武汉:中国地质大学,2009.50-52.Jin S.The Characteristics of Crust-mantle Electrical Structure and Dynamics within Tibetan PlateaufD].Wuhan:China University of Geosciences,2009.50-52.
[5]Jiang W L,Zhang J F,Tian T,et al.Crustal structure of Chuan-Dian region derived from gravity data and its tectonic implications[J].Physics of the Earth and Planetary Interiors,2012,21(2):76-87.
[6]李京昌.滇西怒江断裂带新构造特征[J].地震地质,1998,20(4):312-320.LI Jingchang.Neotectonic Feature Of The Nujiang Fault Zone In Western Yunnan[J].SETSMOLDGY AND GEOLDGY,1998,20(4):312-320.
[7]王晋南,王洋龙,安晓文,等.1976年龙陵地震区断裂活动性研究[J].地震研究,2006,29(4):366-372.WANG Jinnan,WANG Yanglong,AN Xiaowen,YANG Xiangdong,CHANG Zufeng.Activity of the Faults in the 1976LonglingM7.3,7.4 Earthquake Area[J].Journal of Seismological Research,2006,29(4):366-372.
[8]王阎昭,王恩宁,沈正康,等.基于GPS资料约束反演川滇地区主要断裂现今活动速率[J].中国科学(D辑:地球科学),2008(05):582-597.Wang Yanzhao,Wang Enning,Shen Zhengkang,etc.GPS-constrained Inversion of Present-day Slip Rates along Major Faults of the Sichuan-Yunnan Region,China[J].Science in China.Series D:Earth Sciences,2008(05):582-597.
[9]刘宇平,唐文清,赵济湘.青藏高原东部及邻区现代地壳运动GPS监测[M].北京:地质出版社.2010:122-123.LIU Yu-ping,TANG Wen-qing,ZHAO Ji-xiang.Modern crustal movement GPS monitoring of Eastern Qinghai-Tibet plateau and its adjacent areas[M].BeiJing:Geological Publishing House,2010:122-123.
[10]唐方头,宋键,曹忠权,等.最新GPS数据揭示的东构造结周边主要断裂带的运动特征.地球物理学报,2010,33(9):2119-2128.Tang F T.Song J.Cao Z Q.et al.The movement characters of main faults around Eastern Himalayan Syntaxis revealed by the latest GPS data[J].Chinese J.Geophys(in Chinese),2010,53(9):2119-2128.
[11]Manwinder Singh,Ramola R C,Baljinder R Singh,et al.Subsurface soil gas changes associated with earthquakes[J].Nuclear Tracks and Radiation Measurements,1991,19(4):417-420