长江断裂带安徽段上地壳速度结构及基底特征

引用本文

邓晓果, 田晓峰, 杨卓欣, 王夫运, 刘宝峰, 高占永, 郑成龙. 长江断裂带安徽段上地壳速度结构及基底特征[J]. 地震地质, 2020,42(5): 1109-1128.
DENG Xiao-guo, TIAN Xiao-feng, YANG Zhuo-xin, WANG Fu-yun, LIU Bao-feng, GAO Zhan-yong, ZHENG Cheng-long. COMPREHENSIVE INTERPRETATION OF THE UPPER CRUSTAL VELOCITY STRUCTURE AND CRYSTALLINE BASEMENT OF THE CENTRAL YANGTZE FAULT ZONE FROM AIR-GUN SOURCE DATA[J]. SEISMOLOGY AND GEOLOGY, 2020,42(5): 1109-1128. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2020.05.006
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长江断裂带安徽段上地壳速度结构及基底特征

邓晓果, 田晓峰^*, 杨卓欣, 王夫运, 刘宝峰, 高占永, 郑成龙

中国地震局地球物理勘探中心, 郑州 450003

*通讯作者: 田晓峰, 男, 1979年生, 研究员, 主要从事深部探测与构造地质的相关研究, E-mail: tianxf@gec.ac.cn。

〔作者简介〕邓晓果, 女, 1987年生, 2011年于防灾科技学院获地球物理专业学士学位, 工程师, 主要从事深地震测深研究, E-mail: dengyisai@163.com。

收稿日期: 2019-11-11 修回日期: 2020-05-17

基金项目: 国家重点研发计划项目(2018YFC1503200)和国家自然科学基金(41674068, 41790463, 41774071)共同资助

摘要

长江断裂带是中国东部构造体制转换的典型地区, 具有断隆相间、 “一盖多底”的构造特征, 发育了大量金属矿区, 精细的上地壳速度结构和基底图像对该区的成矿作用和构造演化研究具有较为重要的意义。文中以在长江航道内激发的大容量气枪作为震源获得的密集观测数据为基础, 综合利用初至波走时成像、时间项和射线反演等方法, 构建了长江断裂带安庆—马鞍山段的上地壳精细速度结构和基底结构。综合分析研究结果可知, 长江断裂带的上地壳精细速度结构和结晶基底特征显示该区具有断隆相间的构造特征。怀宁盆地是该段上地壳最厚的区域, 其基底埋深约4.5km。庐枞盆地的结晶基底埋深约为4.1km, 沉积盖层呈明显的坳陷盆地形态, 结晶基底及其下方存在相对高速的速度特征。长江断裂带在跨江处的上地壳存在明显的速度横向变化, 显示了长江断裂带切断基底的断裂特征。长江断裂带安徽段基底最浅的区域为铜陵隆起区, 埋深仅为2.2km, 表明铜陵隆起区新生代以来经历了强烈的挤压作用。

关键词: 长江断裂带; 大容量气枪; 上地壳速度结构; 结晶基底

中图分类号:P315.2 文献标志码:A 文章编号:0253-4967(2020)05-1109-20

COMPREHENSIVE INTERPRETATION OF THE UPPER CRUSTAL VELOCITY STRUCTURE AND CRYSTALLINE BASEMENT OF THE CENTRAL YANGTZE FAULT ZONE FROM AIR-GUN SOURCE DATA

DENG Xiao-guo, TIAN Xiao-feng, YANG Zhuo-xin, WANG Fu-yun, LIU Bao-feng, GAO Zhan-yong, ZHENG Cheng-long

Geophysical Exploration Center of CEA, Zhengzhou 450003, China

Abstract

The Yangtze fault zone is a typical tectonic regime transition zone of the eastern China. Tectonically, it is characterized by alternated rifts and uplifts and “several crystalline basements with one sediment cover”. Abundant metal metallogenic deposits are developed. Improvement of the velocity model and basement structure will benefit our understanding and knowledge about the regional tectonics. Large volume airgun sources have been broadly applied to seismic surveys due to significant advantages. For instance, they are environmentally friendly, use lower frequencies, and are repeatable. Several seismic and geological research institutions, such as China Earthquake Administration, carried out a three-dimensional comprehensive sounding using the large volume airgun as the seismic source which was fired at the channel of the Yangtze River in 2015. The source-receiver geometry of this seismic experiment covered the whole Anhui Province which locates at the Middle-Lower Yangtze River. The densest observational area is in the Middle-Lower Yangtze River Metallogenic Belt which is a narrow area along the Yangtze River and consists of the Luzong, Tongling, Ningwu, and Anqing-Guichi ore deposits. The Tanlu fault zone, a giant strike-slip fault of more than 2 000km long, passes through the northwestern margin of this area. Geophysical studies have demonstrated copious geological evidences for the Yangtze fault zone, which is approximately 450km long and crosses central China, extending to the eastern coastal area. The present fault and fold systems are the consequences of the repeated tectonic events since the Mesozoic. We collected and analyzed the seismic data of 20 fixed airgun shot points, then utilized tomography, time term method and head wave traveltime inversion based on ray tracing techniques to model the upper crustal velocity and crystalline basement structure of the Anqing-Maanshan segment beneath the Yangtze fault zone. The profile along the Yangtze River consists of 100 PDS-2 seismometers with a spacing of 2km. We applied the linear and phase weighted stack methods to improve the signal-to-noise ratio of the weak seismic phases from the airgun source. According to the comparison between the linear and phase weighted stack results, the phase weighted stack method significantly improves the quality of the stacked data. We applied the band-pass filter to the stacked data to improve the onset of the first arrival, then picked up the seismic phases and assessed the errors of the picked traveltime. The comprehensive results reveal that the upper crust velocity structure and crystalline basement images show a tectonic feature of alternating rifts and uplifts. The upper crust of the Huaining Basin is the thickest area along the Yangtze River. The basement of the Huaining Basin is around 4.5km and there are Mesozoic lacustrine sedimentary layers whose thickness is about 2km. The crystalline basement depth of the Luzong Basin is 4.1km and the consolidated basin shows clear depression basin shape. This feature of the Luzong Basin reveals that it experienced extensional depression. There is a high-velocity zone beneath the crystalline basement of the Luzong Basin, and the velocity is higher than other areas along the Yangtze River. This high velocity zone shows an arc shape, which agrees with the Paleozoic reflection images by the seismic reflection survey. The profile crosses the Yangtze River in Tongling area and there are obvious velocity differences between the two sides of the Yangtze River. The velocity differences show that the Yangtze faults cut the crystalline basement in Tongling. The upper crust velocity structure of the Tongling area shows clear uplift features and its crystalline basement depth is about 2.2km, which agrees with the arc-reflection structures of the upper crust from the seismic reflection data. This uplift image reveals that the upper crust of the Tongling area has experienced extrusion deformations. The consistency of the seismic reflection imaging results with the near surface geology demonstrates that the large volume air-gun source is applicable to land-based seismic survey.

Keyword: Yangtze fault zone; large-volume airgun; upper crustal velocity structure; crystalline basement

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0 引言

长江断裂带位于大别碰撞造山带的前陆, 在燕山运动时期经历的火山活动和岩浆侵入等被认为与该区域大量金属成矿作用密切相关(董树文等, 2007, 2010; 吕庆田等, 2014)。关于长江断裂带的构造性质及基底特征, 目前仍存在较多争议。秦大正等(1983)对长江断裂带和世界上其它大裂谷进行了综合对比, 认为前者具有大陆裂谷属性; 常印佛等(1991, 1996, 2012)认为长江断裂带是经过多期构造事件后最终在中生代形成的破碎带; 刘湘培等(1988)认为长江断裂带是古老的基底剪切带。此外, 作为规模非常庞大的断裂带, 长江断裂带新生代以来的活动及其地壳稳定性也受到了关注(宋方敏等, 2008)。 2009年以来, 研究者在长江中下游的成矿带开展了大量的深部探测, 获得了该区域主要成矿区的深部构造及横穿长江断裂带若干重要部位的构造图像(董树文等, 2009, 2010, 2011; 史大年等, 2012; 徐涛等, 2013; 吕庆田等, 2014, 2015; 张明辉等, 2015)。

近年来, 在陆上水体中激发大容量气枪震源(Chen et al., 2007; Wang et al., 2011, 2012; Yang et al., 2014)及微弱信号处理提取(Schimmel et al., 2007; Zeng et al., 2016)等技术得到了快速发展, 在内河航道内利用大容量气枪激发地震信号可为获取地下精细结构提供新的途径(陈颙等, 2017)。 2015年, 以大容量气枪作为主要新型震源, 并结合低频可控震源等新型震源, 在长江流域安徽段开展了相关探测工作, 形成了覆盖安徽全省的三维综合探测系统。大容量气枪震源固定激发的信号经叠加后的有效传播距离> 200km, 为获取长江断裂带的精细结构提供了全新的观测数据。田晓峰等(2016)采用线性叠加方法, 基于长江航道内大容量气枪定点激发数据获得了可追踪至60km以远的Pg震相, 并开展了上地壳走时成像的初步研究。 She等(2018)利用主动源激发的面波信号, 获得了沿江主要成矿带浅部的S波波速异常。 Tian等(2018)利用走时成像方法, 构建了区域尺度的上地壳三维精细结构。然而, 长江断裂带安庆— 马鞍山段位于长江腹地, 断陷带内发育了大量断层, 构造复杂, 处于武当— 随县— 张八岭、崆岭— 董岭和江南基底的交会处, 目前尚缺乏完整的基底深部结构图像。

此外, 由于长江两岸沉积层较厚, 并存在较强的人文干扰, 大容量气枪激发的弱信号经线性叠加后信噪比较低, Pg波信号的拾取误差较大, 导致上地壳特别是结晶基底的成像精度不足。本研究使用基于相位加权的叠加方法(Schimmel et al., 2007; Zeng et al., 2016)对气枪信号进行叠加分析, 大大提升了叠后信号的信噪比, 获得了更加可靠的Pg走时数据, 从而可综合利用Pg波走时成像、滑行波射线反演和时间项等方法对长江流域大容量气枪试验观测到的数据进行反演分析, 最终获得了长江断裂带安庆— 马鞍山段的上地壳精细结构和结晶基底特征, 为长江断裂带的研究提供了新的地震学图像。

1 测线位置与地质概况

长江流域大容量气枪探测试验是首次在中国大陆内河航道开展的三维地震综合探测。该试验以大容量气枪为主要震源, 结合低频可控震源等新型震源, 以长江航道为中心布设了超过700台流动地震仪, 形成了9条平行于长江、 2条横跨长江、覆盖安徽全境的三维观测系统。本研究以沿长江布设的密集测线记录到的20次定点激发的地震记录作为研究对象, 观测系统如图 1 所示。沿江布设的测线共包括流动地震仪100台, 观测点距平均为2km, 地震仪连续采样间隔为50ms。

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	图 1 高分辨折射/反射测线位置图Fig. 1 Location map of high-resolution refraction/wide-angle reflection profile.

长江断裂带安庆— 马鞍山段位于长江中游腹地, 是华北块体、秦岭大别造山带与扬子块体的交会带, 属于秦岭大别造山带的前陆区域(图 2)。该区域以郯庐断裂(TFZ)为NW界, 以阳新-常州断裂(YCF)为SE界, 长江穿过其中线, 形成了一个南北100~200km的 “ V” 字型狭长构造带。该条带内发育了安庆— 贵池、庐枞、铜陵和宁芜等矿集区, 被称为长江中下游成矿带(董树文等, 2011)。该区北部的郯庐断裂带附近属于武当— 随县— 张八岭式基底, 沿江的长江断裂带两侧主要为崆岭— 董岭式基底, 阳新-常州断裂SE侧为江南式基底(图2a)(刘刚等, 2016)。这几种不同的基底在该区内均被相同的沉积盖层所覆盖, 形成了 “ 一盖多底” 的构造格局(常印佛等, 1996)。新生代以来, 该区的新构造运动主要表现为弱隆升和垂直差异这2种类型, 且以弱隆升为主。该区的历史地震活动较弱, 以浅源地震为主, 晚更新世以来没有断裂活动(宋方敏等, 2008)。

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	图 2 区域构造图(据常印佛等, 1991修改)及基底分布(据刘刚等, 2016修改)Fig. 2 Tectonic map(modified according to CHANG Yin-fo et al., 1991)and distribution of crystalline basement (modified according to LIU Gang et al., 2016)of the Yangtze fault zone and nearby region.

2 数据处理方法与过程

2.1 数据预处理

本研究利用的数据为20个固定激发点激发的气枪信号在沿长江布设的地震测线上的记录。该测线上共布设PDS-2型数字地震仪100台, 平均观测点距为2km。由于长江沿岸具有较厚的沉积盖层, 且人文干扰较强, 大容量气枪激发的单枪信号被淹没在噪声中, 极难识别(图3a)。利用大容量气枪信号重复性好的特点, 通过多次叠加可大大提升其信噪比(陈颙等, 2017)。为获得地壳深部的地震信号, 对20个固定激发点产生的数据进行线性叠加(图3b)(Wang et al., 2012)和相位加权叠加(图3c)(Schimmel et al., 2007; Zeng et al., 2016), 以提取微弱信号, 最终获得20张共2 000道叠加记录。

图 3 为固定激发点S3的地震记录。其中, 图3a为单枪记录, 从中无法识别有效信号; 图3b为经100次线性叠加获得的记录截面, 从中可明显识别出振幅较强的PmP震相, Pg震相在40km范围内可识别, 经仔细辨认可追踪至60km, 但信噪比较低; 图3c为经215次相位加权叠加获得的记录截面, 其中PmP震相可清晰追踪到150km之外, Pg信号可追踪至超过90km, 且信噪比大大提升。对经相位加权叠加的记录截面进行2~8Hz带通滤波后发现, Pg震相可追踪的距离为80~96km, 与线性叠加方法(田晓峰等, 2016)相比可追踪距离大大提升。最终拾取了上地壳初至波Pg震相912个, 比此前初步研究(田晓峰等, 2016)中的628个Pg震相数量增加了284个。利用互相关方法获取震相的拾取误差(Zelt et al., 1994), 得到震相拾取误差的均值为90~120ms, 与初步研究中采用经验性走时的误差赋值(田晓峰等, 2016)相比, 提升了震相拾取误差的精确度。

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	图 3 固定激发点S3激发产生的地震记录 a 单枪记录; b 100次线性叠加的结果; c 215次相位加权叠加的结果Fig. 3 Observed seismic data from the fixed shot S3.

2.2 初至波走时成像方法

本研究首先采用正则化反演的走时成像方法(Zelt et al., 1998), 对Pg走时进行初至波走时反演, 获取上地壳速度结构模型。在该方法中, 目标函数定义为

$Φ (m) = δ t^{T} C_{d}^{- 1} δt + λ [m^{T} C_{h}^{- 1} m + s_{z} m^{T} C_{v}^{- 1} m]$ (1)

其中, m是模型矢量, δ t是数据残差, C_d是数据协方差矩阵, C_h和C_v分别是水平和垂向平滑度矩阵, λ 是阻尼因子, s_z是水平向与垂向平滑度的权重因子。反演中, 数据协方差矩阵C_d是一个对角矩阵, 其对角元素为Pg震相的到时拾取误差的平方值(Zelt et al., 1998)。水平平滑/粗糙度矩阵C_h每行包含5个非零元素, 分别是1/S_j、 1/S_j、 -4/S_j、 1/S_j和1/S_j的二阶差分值, 这5个元素分别对应第j个反演分块及其在x和y方向相邻的4个分块, S_j为中央分块的先验慢度。在实际反演中, 给定初始速度模型后, 先将该速度模型从正演网格参数化模型转换为反演参数化分块模型, 并将格点速度换算为分块慢度, 即给出了每个反演分块处的先验慢度S_j。 C_v的定义和操作类似, 详见Zelt等(1998)的原文。

该方法数据所拟合的满意度采用统计量χ ²来判断, 其定义为(Bevington, 1969)

$χ^{2} = \frac{1}{N} \overset{N}{\sum_{i = 1}} {[\frac{{t^{o}}_{i} - {t^{p}}_{i}}{σ_{i}}]}^{2}$ (2)

式中, N是观测数据的总量, ${t^{o}}_{i}$ 和 ${t^{p}}_{i}$ 是分别是第i个观测走时和计算走时, σ _i是第i个观测到时的观测误差, 此处相应为震相拾取误差。根据式(2), 当χ ²> 1时, 表明反演结果未能满足数据拟合条件, 为数据拟合不足; 当χ ²< 1时, 表明反演结果过度拟合, 包含了超过数据分辨能力的细结构; 当χ ²=1时, 表明反演结果符合观测误差。

2.3 反演过程及分辨测试

2.3.1 初始模型的选取

不同于传统的经验性选取初始模型的办法(田晓峰等, 2016), 本研究采用Malinowski等(2008)提出的多尺度反演网格迭代选取初始模型的方法。首先, 对优质记录进行视速度分析, 建立一个基于少量炮集的一维模型, 本研究最终所选的一维模型如图4a中的虚线所示。然后, 通过网格尺度不断缩小的非线性迭代反演获得符合数据拟合条件(χ ²=1)的模型后, 对该模型进行一维平均或大尺度平滑成为一维模型, 以此作为反演的初始模型(Malinowski et al., 2008)。

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图 4 a 初始模型的选取; b 初始模型计算的走时曲线与观测走时分布(误差棒为观测走时, 圆点为计算走时); c 初始模型的走时残差直方分布; d 最终速度模型的走时残差直方分布Fig. 4 Initial model for tomography(a), calculated traveltimes(dots)for the initial model and the observed data(error bars)(b), histogram of the traveltime residual for the initial model(c), histogram of the traveltime residual for the final model(d).

本研究在选择初始模型的过程中, 将反演网格分别设置为50km× 10km、 25km× 5km、 10km× 2km、 5km× 2km和2km× 1km, 对每种反演网格均进行5次非线性迭代, 并将第5次迭代产生的模型作为下一种反演网格的初始模型。共经过25次迭代后, χ ²从38.81降低到了1.23。之后, 再对该模型进行一维平均。在平均过程中, 扣除了射线覆盖范围以外的速度值, 最终获得了反演所需的初始模型, 如图4a中黑色实线所示。图4b展示了初始模型计算所得的走时曲线与观测数据的关系。该曲线从观测走时簇中部穿过, 表明该模型与全体观测数据的残差最小, 不会陷入局部极小。

2.3.2 参数选择及反演过程

本研究的模型参数化范围为: 自起始桩号80km至终点桩号350km, 横向全长270km; 垂向为0~20km。该试验探测的平均观测点距为2km, 最小观测点距约为1km, 正演模型适度加密, 采用0.5km× 0.5km的网格进行正演计算, 最终构建了541× 41个正演格点。反演网格采用2km× 1km尺寸, 反演的方块数为270× 20。根据初始模型选取过程中的非线性迭代反演尝试, 将水平向与垂向平滑权重因子s_z设为0.15。在正则化走时反演中, 由于阻尼因子和平滑参数共同约束反演, 一般采用L曲线法选取阻尼因子和平滑参数(Zhang et al., 2003)。然而, 由于地震宽角反射/折射数据反演具有强烈的非线性, 每一步迭代过程中的阻尼因子均不同, 本文所用的初至波走时成像方法在选择阻尼因子时一般采用尝试法(Zelt et al., 1998)。在本研究的反演过程中, 第1次迭代的阻尼因子设为1 000, 通过多次尝试, 每次迭代的阻尼因子值为上次迭代过程中的阻尼因子除以1.08。

最终, 通过31次非线性迭代, 全部912个走时的均方根残差从410.67ms减小到103.37ms, χ ²从23.62降低为1.01。图4c为初始模型走时残差直方分布图, 图4d为最终模型走时残差直方分布图。从图中可以看出, 通过反演, 走时残差从初始模型的大部分残差落在± 300ms收敛至± 100ms以内, 与初始模型相比, 最终模型的反演结果较好地实现了数据拟合。

2.3.3 多尺度检测板分辨测试

为检验反演结果的稳定性和分辨能力, 本研究利用Zelt(1998)和Tian等(2014)提出的多尺度检测板相似度分析方法对结果进行稳定性检验和分辨分析。为了将检测板恢复试验的结果量化, Zelt(1998)提出以检测板恢复相似度R作为模型分辨的参考, 相似度R的定义为

$R = \frac{\overset{M}{\sum_{j = 1}} (D n_{t_{j}} + D n_{r_{j}})^{2}}{2 \overset{M}{\sum_{j = 1}} (D n_{t_{j}}^{2} + D n_{r_{j}}^{2})}$ (3)

其中, D $n_{t_{j}}$ 和D $n_{r_{j}}$ 分别是第j个节点处检测板速度异常的真实值和速度异常的恢复值。 M为一个棋盘格内包含的速度节点总数。该分辨率的定义中, Zelt(1998)指出单个棋盘格内的检测板相似度为0.7, 即为检测板恢复情况良好。该阈值在已开展的走时成像研究中被多次应用(Zelt et al., 2006; Magnani et al., 2009; Tian et al., 2014)。本研究也以0.7作为检测板恢复情况的判断阈值。需要注意的是, 此处的检测板相似度给出的分辨R并非基于反演理论意义上的分辨率定义, 而是基于检测板恢复试验的检测板相似度。

利用前述31次非线性迭代反演得到的模型作为背景模型, 加入± 5%的速度扰动后, 对获得的走时加入± 5%的随机噪音进行反演。在检测板试验的反演过程中, 正、反演参数与前述反演过程参数完全一致, 初始模型为前述第31次迭代的反演结果, 并最终通过31次非线性迭代得到了检测板恢复结果。

图 5 为3个不同尺度检测板的恢复试验结果。图5a、 5c和5e分别为2km× 1km、 5km× 1km和10km× 1km的检测板输入模型, 图5b、 5d和5f分别为相应的恢复结果。利用上述3个检测板恢复结果与检测板输入模型计算每个棋盘格内的相似度, 最终给出了如图6b所示的检测板相似度为0.7的分辨结果。结合射线覆盖(图6c)情况进行分析可知, 在模型所覆盖的大部分范围内, 深度6km以浅的区域成像分辨优于7km, 深度5km以浅的区域成像分辨优于6km。由此, 即获得了长江断裂带较为精细的上地壳速度结构(图6a)。

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	图 5 多尺度检测板恢复试验Fig. 5 Multi-scale checkerboard simulation test.

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	图 6 长江断裂带安徽段的上地壳速度模型(a)、模型分辨(b)及射线覆盖(c)Fig. 6 The final tomographic velocity model(a), the resolution for the velocity model according to the multi-scale checkerboard test(b)and the raypath coverage along the profile(c).

2.4 基底滑行波的射线反演

长江断裂带所在区域主要为崆岭— 董岭式基底(刘刚等, 2016), 是新太古代— 古元古代变质核杂岩。大地电磁的相关结果显示, 基底的电阻明显高于盖层(刘博等, 2018)。基于正则化反演的初至波走时成像能够获得盖层的精细结构, 但由于正、反演方法的特点, 所获得的模型是基于正则化平滑约束的结果, 无法勾画出基底面作为尖锐界面的形态(刘刚等, 2016)。而基于射线追踪的正演试错方法无法计算滑行波, 通常给出的是折射界面(Cerveny et al., 1988)。时间项方法是传统上用来确定基底深度的一种有效方法, 能够利用首波走时反演沿界面的首波滑行速度和滑行界面的深度(Scheidegger et al., 1957; 陈颙等, 1974; 段永红等, 2002; 吴怡等, 2006; 杨卓欣等, 2011)。本研究利用时间项方法反演了沿基底滑行波的走时, 获得了滑行界面的埋深。图7c中的蓝色圆点为时间项反演所获得的基底埋深, 时间项反演所得的滑行波的速度为5.89km/s。利用传统的时间项方法计算时, 通常采用上覆盖层的平均速度, 对于研究区盖层横向变化较大的情况则难以精确约束基底深度(陈颙等, 1974; 段永红等, 2002; 吴怡等, 2006; 杨卓欣等, 2011)。 Hearn等(1986)提出可增加水平分层以更好地约束上覆速度, 利用直达波约束上覆层速度来约束时间项反演的建议。 Valenta等(2007)指出, 为了保持反演过程的稳定, 正则化方法最终获得的模型受一定的平滑约束, 对于某些特殊构造难以精确成像, 同时提出了一种基于先验信息的三维时间项方法, 该方法能够快速地确定滑行界面的埋深。然而, Valenta等(2007)仍然建议研究中应结合包含首波因子算法(Hole et al., 1992)的成像方法综合研究并获取基底结构。

由于部分Pg波为沿着基底界面滑行产生的首波, 这种滑行波对界面形态十分敏感(Cerveny et al., 1971), 因此利用滑行波能够较好地约束基底界面形态。本研究借鉴上述研究的经验和建议, 利用前述层析成像的结果(图6a)给出精确的基底上覆盖层的速度, 并利用基于射线反演的方法, 将初至波到时中的372个基底滑行波单独选出, 利用能够实现滑行波射线追踪和阻尼最小二乘反演方法的RAYINVR软件包进行反演(Zelt et al., 1992), 构建了基底界面的形态及其上覆点的速度, 并结合Pg走时成像、传统时间项和射线反演结果对长江断裂带的基底结构进行综合分析。

射线反演方法(RAYINVR)可采用不规则的网格进行参数化(Zelt et al., 1992)。由于滑行波仅对界面形态和界面处的速度值敏感(Cerveny et al., 1971; Zelt et al., 1992), 为确保基底以上较厚覆盖层速度的准确性, 在反演过程中, 首先将前述初至波走时成像获得的速度模型(图6a)中5.5km/s速度等值线以上的介质视为不能被滑行波走时数据约束的盖层(Valenta et al., 2007)。将初至波走时成像速度模型(图6a)在水平向以10km为网格间距、在垂向将从地表到5.5km/s的速度等值线处平均细分成5层, 所得的模型参数化方案如图7b所示。

图 7b中, 虚线为基于初至波成像模型重采样的界面, 红色方格为界面深度控制节点, 蓝色圆点为速度控制节点, 红色方格和蓝色圆点均基于初至波成像结果重新采样获取, 不参与反演。黑色实线为初始的基底界面位置, 黑色方格和绿色圆点分别为基底界面埋深和速度控制节点, 在反演过程中全部参与反演。

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	图 7 结晶基底上地壳反演结果、初始模型及与成像方法和时间项结果的对比 a 基于射线反演的上地壳速度及基底结构; b 初始模型参数化展示; c 与走时成像方法和时间项方法的结果对比Fig. 7 Results of the head wave inversion and assessment.

结晶基底界面的初始模型深度取前述初至波成像结果中5.7km/s速度等值线(图7b中的黑色实线)的深度, 设基底面上覆初始速度为5.7km/s, 基底面底部的初始速度为5.9km/s, 横向每5km设定1个速度和深度节点。在反演过程中, 设界面深度的不确定性为1km, 速度的不确定性为0.1km/s, 5次反演迭代的阻尼因子均为100。由于射线反演缺乏平滑约束, 每次反演后均对反演获得的界面进行线性平滑, 如果反演结果出现界面交叉的情况, 则将交叉的节点分开。

反演得到的最终模型如图7a所示, 即结晶基底为不连续面的上地壳速度结构。最终模型的均方根走时残差为116ms, χ ²值为1.16。最后, 根据反演的参数给出了速度和界面深度节点的分辨, 如图8c和8d所示, 每个节点的分辨值见表1。一般而言, 反演结果的分辨值> 0.5则可视为已获得了足够的分辨(Zelt et al., 1992; 杨卓欣等, 2011)。

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	图 8 射线反演最终模型的评估 a 滑行波射线覆盖; b 滑行波走时拟合; c 结晶基底上覆速度的反演分辨; d 结晶基底界面反演分辨Fig. 8 Assessment for the inversion model.

表1 滑行波的反演分辨 Table1 Resolution for head wave travel time inversion

3 结果分析和讨论

本研究利用前述Pg走时成像、时间项方法和射线反演方法获得了长江断裂带安庆— 马鞍山段的上地壳精细结构和基底界面形态。 Pg走时成像结果显示, 安庆以南的怀宁盆地到安庆一带的火山盆地是研究区上地壳平均速度最低的区域, 该区域存在厚度> 2km、速度为5.0~5.5km/s的沉积层, 地表速度最低(3.5km/s)的区域位于安庆一带、长江以北的火山盆地内。庐枞盆地是研究区内另一个较厚的沉积集中区域, 盆地中心近地表的速度约为3.5km/s, 5.5km/s速度层以上的沉积厚度> 4km。铜陵以北到芜湖之间为隆起区, 近地表速度> 4.2km/s, 沉积层的水平分层良好, 5.5km/s速度层以浅的沉积层厚度约为2km。芜湖以北到马鞍山为宁芜盆地, 向NE上地壳整体厚度增加, 近地表速度约为4.0km/s, 5.5km/s速度层以上的沉积层厚约5km。

射线反演基于滑行波走时数据, 使用界面和上、下侧速度同时反演的方法, 获得了结晶基底的深度和速度。由于该反演过程中5.5km/s速度层以上的上地壳速度结构均为Pg走时成像结果重新采样获得, 在此不再赘述。射线反演结果显示, 研究区基底埋深最深的区域位于安庆以南的怀宁盆地和安庆一带的火山盆地, 最深为4.48km, 其中结晶基底底部的速度为5.82~5.92km/s, 怀宁盆地一带结晶基底底部的速度最低, 为5.82~5.87km/s, 安庆一带结晶基底底部的速度较高, 为5.88~5.92km/s。庐枞盆地是研究区结晶基底埋深仅次于怀宁盆地的区域, 盆地沉积中心(桩号约210km处)的结晶基底埋深约3.78km, 该区结晶基底底部的速度为研究区内最高, 达5.97km/s。铜陵以北到芜湖为铜陵隆起区, 隆起的中心位置在桩号285km处, 该处的结晶基底埋深约为2.27km, 结晶基底底部的速度为5.90km/s。本研究所获得的观测数据未能覆盖宁芜盆地全部, 反演分辨> 0.5(表1和图 8)的最北区域约位于桩号310km处, 即宁芜盆地的边缘, 该处的结晶基底埋深为2.43km, 结晶基底底部的速度为5.90km/s。图7c对Pg走时成像、时间项方法和射线反演获得的结晶基底结构进行了对比。对比图显示, 通过射线反演和时间项方法获得的结晶基底埋深范围全部位于Pg走时成像速度等值线5.5~5.9km/s范围内, 时间项反演计算所得的范围略大于射线反演分辨> 0.5的范围。同时, 时间项的结果与射线反演结果的一致性较好, 桩号310km以外的基底深度约为3.5km。

研究区最西部的怀宁盆地紧邻大别造山带, 为继承式火山岩盆地, 是长江中下游地区形成最晚的火山盆地(周涛发等, 2011; 薛怀民等, 2016), 该区具有全段最深的基底, 可达约4.5km。坳陷盆地的沉积层序研究显示, 怀宁盆地存在厚度可达2km的中— 晚三叠世湖相沉积, 上覆早中侏罗世河湖相沉积(周涛发等, 2011; 薛怀民等, 2016)。岩浆地球化学研究显示, 怀宁盆地内的火山岩组成呈复合型, 即早期的火山岩属橄榄玄粗岩系列, 晚期的火山岩含钾钙量较高, 属于碱性系列(周涛发等, 2011; 薛怀民等, 2016)。

研究区的另一个坳陷区是庐枞盆地。庐枞盆地结晶基底的埋深呈明显的坳陷盆地形态, 显示了中生代以来经历的伸展坳陷过程(汤家富等, 2010; 周涛发等, 2011)。从庐枞盆地的沉积中心向N, 桩号210km附近的结晶基底上、下侧存在较大的速度差, 且基底面上方的介质速度明显低于周缘。根据SinoProbe在庐枞盆地开展的深地震反射结果(董树文等, 2010; 吕庆田等, 2014)可知, 庐枞盆地内白垩系火山岩盆地底部的双程走时可达2s, 加上处理基准面, 估算其深度约为4.1km, 与本研究射线反演获得结晶基底埋深结果完全一致(董树文等, 2010; 吕庆田等, 2014)。深地震反射的探测结果还显示, 在庐枞盆地的SE界、长江北岸下方存在一系列弧形强反射轴(董树文等, 2010; 吕庆田等, 2014)。该区与本研究所涉及的庐枞盆地位置一致, 射线反演的结果显示, 庐枞盆地结晶基底下方存在速度比其它区域都高的介质属性, Pg走时成像结果也显示出庐枞盆地下方的上隆结构特征。这种弧形的上隆结构与该区古生界的反射特征一致(董树文等, 2010; 吕庆田等, 2014)。

观测测线在铜陵跨过长江, 在铜陵以东观测仪器埋置于长江南岸, 位于铜陵矿集区内。 Pg走时成像结果显示, 在观测点跨江处近地表存在明显的速度横向变化, 显示出长江断裂带与长江航道的密切关系。测线跨江后, 地表速度迅速提升, 约为4.2km/s, 沉积盖层明显上隆, 基底埋深约为2.2km。铜陵以东至芜湖段为铜陵隆起区, 上地壳的沉积盖层呈明显的隆升特征, 在该区域开展的深地震反射结果显示, 在该区上地壳的透明反射区之上存在明显的弧形上拱反射组合 (吕庆田等, 2003), 这与本研究成像结果一致, 暗示了该区域的上地壳经历了强烈的挤压变形过程。物探和航磁资料均支持该区域存在巨大酸性岩基的推测 (常印佛等, 1991)。本研究获得的成像结果为沿长江的基底构造, 该段的成像结果体现的仍是崆岭— 董岭基底特征, 其上隆的速度构造特征和地下1~3km的速度等值线变化(图6a)显示出 “ 两隆夹一坳” 的特征。

4 结论

本研究在长江航道内利用大容量气枪激发的地震信号, 通过微弱信号的相位加权叠加方法, 获得了信噪比较线性叠加方法更高的Pg和PmP等震相记录, 并综合利用初至波走时成像、时间项和射线反演等方法, 构建了长江断裂带安庆— 马鞍山段的上地壳精细结构和基底结构, 获得的上地壳速度结构与在庐枞盆地和铜陵矿集区开展的深地震反射结果形成了良好的一致性印证。研究显示:

(1)对于大容量气枪震源激发的微弱信号, 与线性叠加方法相比, 相位加权叠加方法能够大大提升叠后信号的信噪比, 为地震成像提供更优质的数据。

(2)怀宁盆地是该区域上地壳最厚的区域, 基底埋深为4.5km, 存在厚度可达2km的中生代湖相沉积分层。

(3)庐枞盆地结晶基底的埋深约为4.1km, 沉积盖层呈明显的坳陷盆地形态, 显示出中生代以来经历的伸展坳陷过程。庐枞盆地结晶基底下方存在相对其它区域更为高速的介质属性, 该弧形上隆结构与该区开展的深反射探测获得的古生界的反射特征一致(董树文等, 2010; 吕庆田等, 2014)。

(4)测线在铜陵跨过长江, 观测点所在跨江处的上地壳存在明显的速度横向变化, 显示了长江断裂带是切断基底的断裂。

(5)铜陵隆起区上地壳呈明显的隆升特征, 基底埋深仅2.2km, 与该区域开展的深地震反射显示的上地壳复杂的弧形反射相一致(吕庆田等, 2003), 暗示了铜陵隆起区的上地壳经历了强烈的挤压变形。

致谢本文依托陈颙院士领导和组织的长江安徽段试验探测工作开展相关研究; 陈涛博士对长江安徽实验及主动源探测提出了建议; Colin Zelt教授为本研究提供了软件包并针对数据处理方面提出了建议; 审稿专家为本文提出了宝贵的修改意见。在此一并表示感谢!

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1996

0.0

... 常印佛等(1991, 1996, 2012)认为长江断裂带是经过多期构造事件后最终在中生代形成的破碎带 ...

... 的构造格局(常印佛等, 1996) ...

1991

0.0

... 常印佛等(1991, 1996, 2012)认为长江断裂带是经过多期构造事件后最终在中生代形成的破碎带 ...

... 物探和航磁资料均支持该区域存在巨大酸性岩基的推测 (常印佛等, 1991) ...

2012

0.0

常印佛, 周涛发, 范裕. 2012. 复合成矿与构造转换: 以长江中下游成矿带为例[J]. 岩石学报, 28(10): 3067—3075.

CHANG

Yin-fo

, ZHOU

Tao-fa

, FAN

. 2012. Polygenetic compound mineralization and tectonic evolution: Study in the Middle-Lower Yangtze River valley metallogenic belt[J]. Acta Petrologica Sinica, 28(10): 3067—3075(in Chinese).

The polygenetic compound ore deposits are widely distributed in the world. In order to understand the mineralization process, develop the metallogenic theory and guide ore prospecting and exploration; it is significant to make special research on this kind of deposits. As the intense Mesozoic magmatism rebuild the pre-mineralization in the eastern China, this study take the Middle-Lower Yangtze River Valley metallogenic belt as an example of the eastern China to investigate the mineralization mechanisms of this kind of deposits. To the major mechanisms of the polygenetic mineralization, the authors agree that the superposition and transformation are the basic types of the mineralization enrichment, while the pre-enrichment, inheritance and regeneration of mineralization should be paid more attentions. Generally, there is large-scale mineral enrichment after repetitious inherited and pre-enrichment process. The final formation and Ascription of polygenetic compound ore deposits the Middle-Lower Yangtze River Valley metallogenic belt were related with the Mesozoic tectono-magmatic activities during the change of tectonic regime from compression to extension, which exhibited as "metallogenic explosion". During this process, ore bearing formations (including hydrothermal sediment) and mineralized sedimentary source bed are altered to ore bodies. The mineralization process can be generally divided into two stages; At the early stage (145 to 136Ma), high-K calc-alkaline series intrusion and copper and gold mineralization formed in a strike-slip compression tectonic setting, and at the later stage (135 to 127Ma), shoshonitic series volcanic rocks with iron and sulfur mineralization formed in a strike-slip extensional environment. Both the early and late stages of mineralization widely developed the polygenetic copper, gold, iron, sulfur and Pb-Zn deposit, which are mainly effected by the superimposed reformation. They can he further identified as a typical transitional series of polygenetic compound ore deposits between the magmatic hydrothermal ore deposits and the sedimentary deposits such as the strata-bound skarn type, the sediment-hydrothermal superimposed type, the layered superimposed reformed type, the migrated reformed type and the in situ reformation type, which compose a deposit "family". At the last stage (126 to 123Ma), it formed alkaline volcanic rocks and A-type granitoids with iron, gold, molybdenum and uranium mineralization in the extension environment, which indicated the end of mineralization in the metallogenic belt.

[Chang YinFo; Zhou TaoFa; Fan Yu] Hefei Univ Technol, Sch Resources & Environm Engn, Hefei 230009, Peoples R China.;[Chang YinFo] Dept Land & Resources Anhui Prov, Hefei 230088, Peoples R China.

复合成因矿床分布广泛,把它们单独划分出来进行研究,对于深入认识成矿过程、发展成矿理论和指导找矿勘探,均有重要意义。鉴于中国大陆东部中生代岩浆作用强烈,对前期成矿作用的影响也很明显,因此本文以长江中下游成矿带为例,评介了复合成矿作用的几种主要机理,认同前人提出的叠加和改造是其基本类型,但预富集作用也应重视,同时也不能忽视继承成矿和再生成矿,特别是继承和预富集联合多次出现时,可以形成区域性成矿元素大规模富集。同时,本文还将它们放在区域构造体制和机制转化演化过程中加以考察,进一步明确它们在中生代构造体制转换以前主要以沉积(含热水沉积)成因的含矿建造、矿源层或矿(胚)层产出,而矿床的最终形成与就位则主要与新构造体制下由挤压向引张转化的过渡环境中构造-岩浆活动有关,呈现出"成矿大爆发"的现象。其中早期(145~136Ma)构造机制是以走滑挤压作用为主,形成与高钾钙碱性岩系有关的铜金矿化。晚期(135~127Ma)以走滑引张作用为主,形成了与橄榄安粗岩系有关的铁硫矿化。但这两期都有广泛发育的以叠加改造为主的复合成因铜、金、铁、硫及铅锌矿床,从而在典型的岩浆热液矿床和沉积矿床之间形成了一套过渡性矿床序列(层控矽卡岩型→沉积热液叠加型→层控叠改型→迁移式改造型→原地式改造型),构建了一个矿床"家族"。末期(126~123Ma)以引张作用为主,出现碱性火山岩和A型花岗岩类,伴随铁、金、钼、铀等矿化,成矿带的成矿活动随之进入尾声。

... 常印佛等(1991, 1996, 2012)认为长江断裂带是经过多期构造事件后最终在中生代形成的破碎带 ...

1974

0.0

陈颙, 陈运泰. 1974. 晋中南地区地壳结构的初步研究[J]. 地球物理学报, 17(3): 186—199.

CHEN

Yong

, CHEN

Yun-tai

. 1974. A preliminary research on crustal velocity in central southern region of Shanxi[J]. Chinese Journal of Geophysics, 17(3): 186—199(in Chinese).

In this study preliminary results are presented for the investigation of the crustal structure of the South- central part of Shansi Province by use of the time-term method, applied to the material obtained during several industrial explosions carried out in Chang-an, Dai Hsien and Taigu. An adaptation of the method is made for those explosions of which the origin times are not known. The velocity just below the M-discontinuity is found to be 7.95±0.04 km/sec. Assuming an average velocity of 6.4 km/sec, for the crust, the time-terms for 41 locations were obtained, whence the corresponding depths of the M-discontinuity were computed by inversion. The relation between these and the seismicity or mechanism of earthquakes in this area is briefly discussed.

Institute of Geophysics, Academia Sinica

本文是对陕西长安、山西代县和太谷等地工业爆破的资料采用时间项法研究晋中南地壳结构的初步成果。文中首先结合长安爆破观测资料的总结,对时间项方法作一介绍。为使用太谷等缺乏起爆时刻的爆破资料,对时间项方法作了一些改进,使对于那些未有起爆时刻的爆破资料亦能用于确定时间项。使用上述爆破和各台记录的初动到时获得了晋中南地区的界面速度为7.95±0.04公里/秒,求得了41个点的时间项,取莫霍面以上介质的平均速度v 0 =6.4公里/秒反演求得了各点的莫霍界面深度,并对所得的结果结合晋中南地区的地震活动性及部分地震震源机制结果进行了初步的分析和讨论。

... 陈颙等, 1974 ...

... 利用传统的时间项方法计算时, 通常采用上覆盖层的平均速度, 对于研究区盖层横向变化较大的情况则难以精确约束基底深度(陈颙等, 1974 ...

2017

0.0

... , 2016)等技术得到了快速发展, 在内河航道内利用大容量气枪激发地震信号可为获取地下精细结构提供新的途径(陈颙等, 2017) ...

... 利用大容量气枪信号重复性好的特点, 通过多次叠加可大大提升其信噪比(陈颙等, 2017) ...

2009

0.0

... 2009年以来, 研究者在长江中下游的成矿带开展了大量的深部探测, 获得了该区域主要成矿区的深部构造及横穿长江断裂带若干重要部位的构造图像(董树文等, 2009, 2010, 2011 ...

2011

0.0

董树文, 马立成, 刘刚, 等. 2011. 论长江中下游成矿动力学[J]. 地质学报, 85(5): 612—625.

DONG

Shu-wen

, MA

Li-cheng

, LIU

Gang

, et al. 2011. On dynamics of the metallogenic belt of middle-lower reaches of Yangtze River, eastern China[J]. Acta Geologica Sinica, 85(5): 612—625(in Chinese).

The Middle Lower Reaches of Yangtze River is a well-known Mesozoic metallogenic belt in central eastern China, which has been the key base of mineral supply for the Yangtze industry corridor, and then is nicknamed The Industry Cradle. In view of geological evolution and metallogenic dynamics, the Middle Lower Yangtze metallogenic belt has its own distinguishing features in China, even in the world. Firstly, the tectonic background and processes had experienced the environments from plate margin to intra plate during T2-J2, and mineralization occurred in transformation from compression to extension (145~130 Ma). Secondly, diagenesis and mineralization in the belt were controlled by base structure and deep process, and related to its own basement. In conclusion, the Middle Lower Yangtze mineralization had occurred through the whole Yanshanian epoch (165～120Ma) and distinctly recorded the imprint of subduction of Pacific Plate during Late Jurassic to Early Cretaceous.

长江中下游是我国东中部著名的中生代金属成矿带，更是长江工业走廊的矿物供应基地，素称工业摇篮。从地质演化和成矿动力学角度，长江中下游成矿带在我国、甚至世界上具有鲜明的特色。首先，成矿大地构造背景和过程经历了由板缘到板内的环境，成矿作用发生在挤压向伸展的转换过程；其次，成岩成矿受基底构造和深部作用控制、与特有的基底有关；最后，长江中下游成矿作用贯穿于“燕山运动” 的始终，深刻地记录了太平洋板块作用的影响。本文对上述重大问题提出粗浅的见解，供讨论。

... 贵池、庐枞、铜陵和宁芜等矿集区, 被称为长江中下游成矿带(董树文等, 2011) ...

2010

0.0

董树文, 项怀顺, 高锐, 等. 2010. 长江中下游庐江—枞阳火山岩矿集区深部结构与成矿作用[J]. 岩石学报, 26(9): 2529—2542.

DONG

Shu-wen

, XIANG

Huai-shun

, GAO

Rui

, et al. 2010. Deep structure and ore formation within Lujiang-Zongyang volcanic ore concentrated area in middle to lower reaches of Yangtze River[J]. Acta Petrologica Sinica, 26(9): 2529—2542(in Chinese).

To explore the crustal-depth structures in a volcanic depression, iron and sulfur ore concentrated area, and study deep process ore-formation within Lujiang-Zongyang area, along the metallogenic belt of Middle-Lower Reaches of Yangtze River during Cretaceous, the deep-probe project was carried. 150km long deep reflection seismic profile (recorded 30 seconds) across volcanic depression, 20km shallow high resolution reflection seismic profile in Luohe larger iron deposit (20km), magnetotelluric profiles, high resolution gravity and magnetic profiles parallel to the seismic profile were finished since 2006~2009, and the images of whose crustal fine structure and electromagnetic structures were revealed, simultaneously the regional tectonic analysis and volcanic rocks chronology were obtained. The all of new evidences indicated that Lu-Zong volcanic depression and iron deposits was controlled by a deep fault, NE-SW tending Luohe fault, which cut through crust to MOHO and the half-round sharp ("ear-sharp") depression was an asymmetric volcanic eruption along Luohe fault expending from west to east, excluded the hypothesis that another half buried in west of Luohe fault under red bed basin. The Luohe fault is considered as the tectonic channel linking from surface to mantle resulting in the upwelling and eruption of deep fluid, and magma chambers in mid-crust along bi-later of this channel can distinguished form "light spots" of the reflectors. The multi-layer borders were identified through the volcanic depression, the depth of Cretaceous volcanic rocks and Jurassic sedimentary strata is 4~5km (the depth of volcanic rocks is ca.3km), the depth of sequence of deformated layers from Sinian to Triassic is ca.18~20km, and the middle-lower crust consists of metamorphic basements.The MOHO has gentle north-west dipping and ca.33~31km depth. Tan-Lu fault, a larger left slip displacement fault, extended to MOHO with steep dipping, the width is ca.10km. Thereby, the deep process and mechanics of the mineralization within Lu-Zong volcanic depression during Early Cretaceous (132~127Ma) were revealed.

为探测长江中下游成矿带庐江-枞阳白垩纪火山岩盆地和铁、硫矿集区深部构造和地壳结构,探讨成矿深部控制条件,作者完成了穿越火山岩盆地的深反射地震剖面(150km,记录30s)和罗河铁矿区浅层高分辨反射地震剖面(20km),以及平行剖面的大地电磁、高精度重磁剖面,揭示了矿集区全地壳精细结构和电磁结构,同时开展区域构造测量和火山岩年代学研究,获得了新的认识。证实"耳状"的庐-枞火山岩盆地是一个沿北东向罗河断裂向东侧发育的非对称火山盆地,排除了另一半被断在西侧红层之下的判断;罗河断裂是一条切穿MOHO的深断裂,倾向南东,是引导地幔流体和岩浆上涌和喷发的通道,在中地壳形成岩浆房(反射亮斑);鉴别出多层界面,火山岩-侏罗系厚度约4~5km(其中火山岩厚度约3km),三叠系-震旦系变形层底界深度大致18~20km,变质基底组成中下地壳,MOHO平缓向北西倾,深度33~31km;追踪郯-庐断裂带的深部产状,陡立延伸到MOHO,宽约10km。从而揭示了早白垩系(132~127Ma)庐-枞火山岩矿集区深部过程与成矿、控矿作用。

... 0 引言长江断裂带位于大别碰撞造山带的前陆, 在燕山运动时期经历的火山活动和岩浆侵入等被认为与该区域大量金属成矿作用密切相关(董树文等, 2007, 2010 ...

... 根据SinoProbe在庐枞盆地开展的深地震反射结果(董树文等, 2010 ...

... 1km, 与本研究射线反演获得结晶基底埋深结果完全一致(董树文等, 2010 ...

... 深地震反射的探测结果还显示, 在庐枞盆地的SE界、长江北岸下方存在一系列弧形强反射轴(董树文等, 2010 ...

... 这种弧形的上隆结构与该区古生界的反射特征一致(董树文等, 2010 ...

... 庐枞盆地结晶基底下方存在相对其它区域更为高速的介质属性, 该弧形上隆结构与该区开展的深反射探测获得的古生界的反射特征一致(董树文等, 2010 ...

2007

0.0

董树文, 张岳桥, 龙长兴, 等. 2007. 中国侏罗纪构造变革与燕山运动新诠释[J]. 地质学报, 81(11): 1449—1461.

DONG

Shu-wen

, ZHANG

Yue-qiao

, LONG

Chang-xing

, et al. 2007. Jurassic tectonic revolution in China and new interpretation of the Yanshan Movement[J]. Acta Geologica Sinica, 81(11): 1449—1461(in Chinese).

随着一系列新构造观察资料和高精度同位素测年数据的累积,加深了对发生在中国东部晚侏罗世―早白垩世时期构造变革事件的认识,对燕山运动的性质、时限和动力学内涵有了新的诠释。中―晚侏罗世初期(165±5Ma)东亚多板块拼贴运动学发生重大调整,构造体制发生重大转换,启动了以中朝地块为中心、来自北、东、南西不同板块向东亚大陆"多向汇聚"的构造新体制,形成以陆内俯冲和陆内造山为特征的东亚汇聚构造体系。同时大陆地壳岩石圈发生显著增厚,并紧随早白垩世以剧烈的大陆岩石圈伸展和火山―岩浆活动为特征的岩石圈巨量减薄和克拉通破坏,导致燕辽生物群灭绝和热河生物群兴盛的重大生物群更替,成为中国大陆和东亚重大构造变革事件,这是燕山运动的基本内涵。本文依据燕山运动构造变形型式、动力学背景以及产生的深部过程,将"燕山运动"定义为起始于165±5Ma的"东亚多向汇聚"构造体制及其形成的广泛陆内造山和构造变革,并将中国东部岩石圈巨量减薄视作燕山期陆内造山和陆内变形的后效。

2002

0.0

... 段永红等, 2002 ...

2018

0.0

... 大地电磁的相关结果显示, 基底的电阻明显高于盖层(刘博等, 2018) ...

2016

0.0

... 董岭式基底, 阳新-常州断裂SE侧为江南式基底(图2a)(刘刚等, 2016) ...

... 董岭式基底(刘刚等, 2016), 是新太古代#cod#x02014 ...

... 基于正则化反演的初至波走时成像能够获得盖层的精细结构, 但由于正、反演方法的特点, 所获得的模型是基于正则化平滑约束的结果, 无法勾画出基底面作为尖锐界面的形态(刘刚等, 2016) ...

1988

0.0

... 刘湘培等(1988)认为长江断裂带是古老的基底剪切带 ...

2014

0.0

吕庆田, 董树文, 史大年, 等. 2014. 长江中下游成矿带岩石圈结构与成矿动力学模型: 深部探测(SinoProbe)综述[J]. 岩石学报, 30(4): 889—906.

LÜ

Qing-tian

, DONG

Shu-wen

, SHI

Da-nian

, et al. 2014. Lithosphere architecture and geodynamic model of middle and lower reaches of Yangtze metallogenic belt: A review from SinoProbe[J]. Acta Petrologica Sinica, 30(4): 889—906(in Chinese).

The lithosphere structure and deep processes are keys to understanding the formation of ore-district and metallogenic province. Lithosphere-scale process could create big footprints or signatures which can be observed by geophysics methods. To better understand the deep dynamic of the major metallogenic province, the authors has conducted an integrated deep exploration across Middle and Lower Reaches of Yangtze Metallogenic Belt (YMB) in eastern China, these included broadband seismic, deep reflection seismic, wide-angle reflection seismic and magnetotelluric sounding. The findings based on the data processing and inversion of these integrated geophysical exploration include: (1) Lower velocity body at the top of upper mantle and a SW dipping high velocity body with center depth at 300km, were imaged by teleseismic tomography beneath YMB; (2) S-wave receive function evidence the thinning of the lithosphere beneath the YMB to 50 similar to 70km; and SKS, SKKS shear wave splitting results show NE parallel fast-wave polarization direction which parallel with the regional tectonic lineament; (3) The reflection seismic data reveals strong NW-SE upper crustal contraction deformation, characterized as tight fold, thrust fault and nappe. The "crocodile" reflection structures are found beneath the Ningwu volcanic basin, Changjiang deep fault and Tan-Lu fault, indicating the decoupled deformation process of the upper and lower crust. Overall, the seismic data show evidence for an introcontinental orogen with lower crust and upper mantle subduction and imbrication; (4) Refraction seismic and MT data provide velocity and resistivity distribution across the YMB, and show a general agreement with the tectonic units. Based on the results of the integrated geophysical exploration, combining with the recent geochemistry results, a geodynamic model is proposed for the YMB. The model suggests that Middle and Later Jurassic introcontinental subduction, lithosphere delamination, mantle-derived magmatic underplating and MASH process are responsible for the formation of this world-class metallogenic belt.

[Lu QingTian; Shi DaNian; Zhang YongQian] Chinese Acad Geol Sci, Inst Mineral Resources, MLR Key Lab Metallogeny & Mineral Assessment, Beijing 100037, Peoples R China.;[Dung ShuWen] Chinese Acad Geol Sci, Beijing 100037, Peoples R China.;[Tang JingTian] Cent S Univ, Sch Geosci & Infophys, Key Lab Metallogen Predict Nonferrous Met, Minist Educ, Changsha 410083, Hunan, Peoples R China.;[Jiang GuoMing] China Univ Geosci, Sch Geophys & Informat Technol, Beijing 100083, Peoples R China.;[Xu Tao] Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China.

岩石圈结构和深部过程对理解成矿带和大型矿集区的形成十分重要。岩石圈尺度的地球动力学过程将在地壳中留下各种结构的或物质的“痕迹”，这些“痕迹”可以通过地球物理的手段去探测。为深入理解长江中下游成矿带形成的深部动力学过程，作者在国家深部探测专项（SinoProbe）和国家自然科学基金重点项目支持下，在长江中下游成矿带开展了综合地球物理探测。方法包括宽频地震、深地震反射、广角反射/折射和大地电磁测深。数据处理和反演结果取得一系列新发现：（1）成矿带上地幔顶部存在低速体，在中心深度300km处有一向SW倾斜的高速体；（2）S波接收函数证实成矿带岩石圈较薄，只有50~70km；横波分裂结果显示，成矿带上地幔各向异性方向和强度与邻区有较大区别，显示平行成矿带（NE-SW向）的上地幔变形和流动；（3）深反射地震揭示成矿带上地壳曾发生强烈挤压变形，以紧闭褶皱、逆冲和推覆为特征；在宁芜火山岩盆地、长江断裂带和郯庐断裂之下出现“鳄鱼嘴”构造，指示上下地壳在挤压变形过程中解耦；深反射地震证实发生过陆内俯冲和叠瓦，并认为是岩石圈增厚和拆沉的主导机制；（4）广角反射和大地电磁反演给出了跨成矿带地壳剖面的速度和电性结构，速度和电阻率分布总体上与构造单元相吻合。本文分析和解释了这些发现的地质意义，并结合近年在长江中下游地区的地球化学研究进展，提出了成矿带地球动力学模型。该模型认为：中、晚侏罗世陆内俯冲、岩石圈拆沉、幔源岩浆底侵和MASH过程造就了长江中下游世界级成矿带的形成。

... 吕庆田等, 2014) ...

... 吕庆田等, 2014, 2015 ...

... 吕庆田等,2014)可知, 庐枞盆地内白垩系火山岩盆地底部的双程走时可达2s, 加上处理基准面, 估算其深度约为4 ...

... 吕庆田等, 2014) ...

2003

0.0

... 铜陵以东至芜湖段为铜陵隆起区, 上地壳的沉积盖层呈明显的隆升特征, 在该区域开展的深地震反射结果显示, 在该区上地壳的透明反射区之上存在明显的弧形上拱反射组合 (吕庆田等, 2003), 这与本研究成像结果一致, 暗示了该区域的上地壳经历了强烈的挤压变形过程 ...

... 2km, 与该区域开展的深地震反射显示的上地壳复杂的弧形反射相一致(吕庆田等, 2003), 暗示了铜陵隆起区的上地壳经历了强烈的挤压变形 ...

2015

0.0

... 吕庆田等, 2014, 2015 ...

1983

0.0

秦大正, 刘昌森, 丁颂华, 等. 1983. 长江断裂带东延问题及裂谷特性的讨论[J]. 地震地质, 5(2): 69—78.

QIN

Da-zheng

, LIU

Chang-sen

, DING

Song-hua

, et al. 1983. Research on the extending to the east of the Yangtze fault zone and its characteristics of rifting[J]. Seismology and Geology, 5(2): 69—78(in Chinese).

According to the effect of water infiltrating in porous rocks and the generalized classification of earthquake by Bell and Nur and Mogi,it is suggested that the process of infiltrating of water may be responsible for the unstable and inhomogeneous distributioneh of the effective stress over the reservoir area. The characteristics of the earthquake sequence in the reservoir are related to this kind of stress distribution. The effect of infiltrating water on the main shock is discussed. The permeability can be found to be 10 -4 darcy. It is suggested that the tectonic stress in the reservoir area is not in the critical state; water in the reservoir area collected along with underground water to form a new water system; and then water widely infiltrated into deeper parts with the pore pressure increasing and the tectonic stress concentrating to cause the main shock. On the basis of the Coulomb criterion,the transformation of the stress field is studied. The transformation of the stress field after the main shock may account for different stress state of earthquake sources between the foreshock and the aftershock.

Department of Geophysics, Peking University

据具有孔隙的岩石中水的渗透作用及 Mogi 的地震分类原则,提出水的渗透过程形成了库区有效应力分布的非稳定的不均匀状态,水库地震的序列特点与其密切相关;讨论了水的渗透对引起主震的作用,得出水库区的渗透率约为10 -4 达西,认为在蓄水前库区的构造应力场未达到临界状态,库水与地下水形成新水系,后在此基础上进一步渗透,孔隙压力增加,构造应力进一步集中,激发主震;根据库仑准则讨论了应力场的转换,提出主震后应力场的转换是造成前震和余震的震源应力场方向不同的原因。

... 秦大正等(1983)对长江断裂带和世界上其它大裂谷进行了综合对比, 认为前者具有大陆裂谷属性 ...

2012

0.0

史大年, 吕庆田, 徐文艺, 等. 2012. 长江中下游成矿带及邻区地壳结构: MASH 成矿过程的 P 波接收函数成像证据?[J]. 地质学报, 86(3): 389—399.

SHI

Da-nian

, LÜ

Qing-tian

, XU

Wen-yi

, et al. 2012. Crustal structures beneath the mid-lower Yangtze metallogenic belt and its adjacent regions in eastern China: Evidences from P-wave receiver function imaging for a MASH metallization process?[J]. Acta Geologica Sinica, 86(3): 389—399(in Chinese).

Using the passive-source seismic data collected during November 2009 to March 2011 in a multidisciplinary cross-section in the mid-lower Yangtze metallogenic belt, we conducted receiver function imaging etc., and obtained images with great clearance of the crust and upper mantle structures in the study region. First, the receiver function image shows the Moho depth varies significantly along the profile in the study region, and a “mantle uplift” is shown just beneath the Yangtze metallogenic belt (will refer to the Nanjing-Wuhu ore district of the Yangtze metallogenic belt in this paper if not stressed, the same below). In the southeast section of the northern margin of Yangtze craton, Moho topography is relatively stable with depths of about 30km, and in the vicinity of the Jiangnan fault and the Maoshan fault, Moho surface is shown rugged up, and to the centre part of the cross-section or beneath the Nanjing-Wuhu ore district, the Moho is shown uplift obviously with a depth of only about 28km, below the Tan-Lu fault zone the Moho is seen deepened up to a depth of 36km, and further north to the southern margin of North China block, Moho depth is shown gradually restored to depth of about 32km or to the level of the average depth. Secondly, we found in the results of receiver function image the lower crus of the Yangtze metallogenic belt is different from its surrounding in the structures, and the lower crust of the Yangtze metallogenic belt is significantly seismic azimuthal anisotropic. The lower crust beneath the northern margin of Yangtze craton is seen in a nearly horizontal structure with high velocity but without appearent seismic anisotropy; Contrastly, the lower crust beneath the Yangtze metallogenic belt is although in a nearly horizontal structure, but shown to be in high velocity for seismic waves propagated approximately along the strike of the metallogenic belt, and shown to be in low velocity for seismic waves propagated approximately normal to the strike, which means that the lower crust of the metallogenic belt exists belt-parallel seismic anisotropy. We interprete this phenomenon is due to the melting, flow and mineral crystal orientation in the lower crust. Finally, we observed a converted interface extened from the shallow crust to the middle and lower crust on the northern side of the TanLu fault in the southern margin of North China, which dips to southeast and interpreted to be related to the crustal extension within the Hefei Basin. In addition, we found that the \"mantle uplift structure\" observed in the receiver function result is in a good correspondence to a low velocity zone in the upper mantle at depths of about 150km beneath the metallogenic belt on the teleseismic P wave tomogram (Jiang Guoming et al., in another paper). We interpreted both of them to be a result of asthenosphere upwelling.Integrated the results from the seismic imaging of receiver function with the one from the teleseismic P wave tomography and previous research results in magmatic rocks and so on, we suggest that the formation of the Yangtze metallogenic belt to be a result MASH mineralization. First, the upwelling asthenosphere led to a extensional environment in the the Yangtze metallogenic belt and its surrounding regions, and resulted in a series of extensional structures in the middle to upper crust; then, upwelling asthenospheric materials underplated into the lower crust of the Yangtze metallogenic belt, and occurred assimilation when mixed with the lower crustal material in situ, resulted in the formation of adakitic-like magma; Then adakitic magma rised up along the extensional and the decollemental structures in the shallow crust as intrusive bodies, and reacted with country rock to form the mineral deposits.

利用长江中下游成矿带多学科深部探测剖面于2009年11月至2011年3月间采集的天然地震数据，通过天然地震接收函数成像等方面研究，得到了研究区地壳和上地幔结构的清晰图像。接收函数成像结果显示研究区内Moho面深度存在着明显起伏变化，在长江中下游成矿带(指剖面穿过的长江中下游成矿带宁芜矿集区，下同)下方存在“幔隆构造”。在剖面东南端的扬子克拉通北缘，Moho面相对稳定，深度约为30km，在茅山和江南断裂附近，Moho面存在上下起伏现象，在剖面中部的宁芜矿集区下方，Moho面存在明显隆起，深度只有28km左右，在郯庐断裂带下方Moho面明显加深，深度达到36km，进一步向北到华北地台南缘，Moho面深度逐渐恢复到了32km左右的平均深度水平。其次，我们在接收函数成像结果中发现，长江中下游成矿带与其周边的下地壳结构存在着明显的差异，成矿带的下地壳具有显著的地震波方位各向异性。扬子克拉通北缘的下地壳呈高速的近水平状结构，地震波各向异性特征不明显；与此成对比的是，长江中下游成矿带的下地壳虽然也呈近水平状结构特征，但是，对于沿成矿带走向方向传播的地震波，其下地壳表现为高速特征，而对于垂直于成矿带走向方向上传播的地震波，其下地壳又表现为低速特征，这意味着长江中下游成矿带的下地壳存在平行于成矿带走向的地震波各向异性，我们解释其是下地壳熔融并沿成矿带走向流动导致矿物晶体定向排列的结果。最后，我们在郯庐断裂以北的华北地台南缘观测到一条从上地壳延伸到中下地壳的、南东向方向倾斜的转换界面，推测它可能与合肥盆地内部的地壳伸展过程有关。此外，我们发现接收函数成像结果中观测到的“幔隆构造”与远震P波层析成像结果在成矿带下方150km深度上显示的上地幔低速异常(江国明等，另文发表)存在良好的对应关系，我们解释它们是软流圈物质上涌的遗迹。综合天然地震接收函数成像结果，以及远震P波层析成像证据和前人关于岩浆岩等方面的研究成果，我们认为长江中下游成矿带的形成是MASH成矿作用的结果。首先，软流圈物质上涌导致了长江中下游成矿带及其周边拉张环境的形成，在中上地壳形成了一系列伸展构造；然后，软流圈物质通过底侵进入长江中下游成矿带的下地壳并与原下地壳物质发生同化作用，形成埃达克质的岩浆；接着，埃达克质的岩浆沿着伸展、拆离构造上升到地壳浅部形成不同层次岩浆房和侵入岩体，并与围岩作用形成矿床。

... 史大年等, 2012 ...

2008

0.0

宋方敏, 邓志辉, 马晓静, 等. 2008. 长江谷地安庆—马鞍山段新构造和断裂活动特征[J]. 地震地质, 30(1): 99—110.

SONG

Fang-min

, DENG

Zhi-hui

, MA

Xiao-jing

, et al. 2008. Neotectonics and fault activity in the Anqing-Ma'anshan section of the Changjiang River valley[J]. Seismology and Geology, 30(1): 99—110(in Chinese).

The neotectonic movement and characteristics of fault activity in the Anqing-Ma'anshan section of the Changjiang River valley are analyzed on the basis of data obtained from field investigation,shallow seismic prospecting and drilling. The results show that during neotectonic time this river valley section and its both sides as a whole was dominated by weak and intermittent uplift movement. As a consequence,owing to the effect of the activity of NE-and NNE-trending faults,relatively strong vertical differential movement occurred in Wuwei-Anqing area during Paleogene-Neogene,and had continued to early and middle Pleistocene. The NE-NNE-trending and NW-trending faults were developed in the bed rocks of the valley and its both sides. The former was formed during Indo-Chinese epoch,while the later was formed during Yanshan epoch. The most recent active period of the larger faults controlling the development of Cenozoic Basins is middle Pleistocene,while the newest activity of the relatively small faults developed within pre-Cenozoic group is pre-Quaternary. The Quaternary system in the valley is \{10～\}50m thick,consisting mainly of Pleistocene-Holocene deposits. The isopach of these deposits is smoothly distributed,indicating normal valley deposition. Seismic activity along the valley and its both sides is relatively weak,and historically only 4 destructive earthquakes have been recorded. Among these events,the largest one is the M 5(3/4) earthquake occurring at Chaohu in 1585,and the other events including one with M 5(1/4) and two with M 4(3/4). Since the beginning of instrumental records in 1970,the largest magnitude that has been recorded so far is ML 3.7. All these results may provide better constraints on the assessment of the crustal stability for this river valley section.

Institute of Geology, China Earthquake Administration, Beijing 100029, China

根据地面地质调查、浅层地震勘探、钻探等成果,分析了长江谷地安庆—马鞍山段的新构造运动和断裂活动特征。资料表明,该段谷地及其两侧新构造时期总体以弱的间歇性隆升运动为主,其中无为、安庆一带受NE,NNE向断裂活动的影响,古近纪—新近纪有较强烈的垂直差异运动,并一直持续到早、中更新世。谷地及其两侧基岩中发育NE—NNE向与NW向2组断裂,前者主要形成于印支期,后者主要形成于燕山期,其中控制新生代盆地发育且规模较大的断裂最新活动时代为中更新世,而发育在前新生界内部且规模较小的断裂最新活动时代为前第四纪。谷地中第四系厚度为10～50m,主要为晚更新世—全新世堆积,等厚线总体分布平稳,为正常的河谷堆积。沿谷地及其两侧地震活动较弱,历史上仅发生4次破坏性地震,最大地震为1585年巢湖南5(3/4)级地震,另有1次5(1/4)级地震、2次4(3/4)级地震,1970年有仪器记载以来,记录到的最大地震为 M L 3.7。这些特征有利于该段谷地的地壳稳定性评价。

... 此外, 作为规模非常庞大的断裂带, 长江断裂带新生代以来的活动及其地壳稳定性也受到了关注(宋方敏等, 2008) ...

... 该区的历史地震活动较弱, 以浅源地震为主, 晚更新世以来没有断裂活动(宋方敏等, 2008) ...

2010

0.0

汤家富, 陆三明, 李建设, 等. 2010. 安徽庐枞火山岩盆地与邻区基底构造变形, 形成演化及其对矿床分布的控制[J]. 岩石学报, 26(9): 2587—2597.

TANG

Jia-fu

, LU

San-ming

, LI

Jian-she

, et al. 2010. The basement structural deformation, evolution and its control action on deposit distribution in Luzong volcanic basin and its adjacent area in Anhui Province, China[J]. Acta Petrologica Sinica, 26(9): 2587—2597(in Chinese).

In this article, the tectonic background of formation and the characters of the two important unconformity interface and two kinds of faults in Luzong volcanic basin are analyzed. The deformation characteristics of the two stage overlapping-folds and the stratigraphic sequence and spatially distributing feature in Indosinian folding basement in Luzong volcanic basin and adjacent areas are discussed. And it introduced the expression and controversy of Jinzi Movement and Nanxiang Movement in Indosinian in this areas. Based on the unconformable contact between Dongmaanshan Formation and Nanlinghu Formation in the area of Chaohu and Hexian recently, the existence of the Jinzi Movement is further confirmed,which discussed the kinematic base and possible dynamic conditions formed by the deformation of the two stage Indosinian folds. Through the reunderstanding of metallogenic background, the mineralizing characteristics and prospecting direction of the three types deposits are summarized (volcanic-related iron deposits, neutral-acid intrusive rocks-related porphyry copper and lead-zinc deposits,contact metasomatic type and stratabound iron type of the iron and copper deposits). It emphasized the Yanshanic structural especially faulted structure control on magma intrusion and volcanic action and related mineralization. And it discussed the rock-controlling and ore-controlling structure conditions of typical deposits.

本文简略分析了庐枞火山岩盆地形成的地质构造背景及火山岩盆地内两个重要不整合界面,两类不同性质断裂的特征。文中详细论述了庐枞及邻区印支期褶皱基底中两期叠加褶皱变形特征及其对地层序列与空间展布的控制。介绍了区内印支期金子运动与南象运动的存在表现及争议。根据近期在巢湖、和县一带普遍发现东马鞍山组与南陵湖组间不整合接触关系,进一步肯定了金子运动的存在,从而探讨了印支期两期褶皱变形形成的运动学基础及可能形成的动力学条件。在对上述成矿背景重新认识的基础上,总结了区内三类矿床的成矿特征及找矿方向(与火山岩有关的铁矿、与中酸性侵入岩有关的斑岩型铜矿及铅锌矿、接触交代型与层控型铁铜矿)。强调了燕山期构造,特别是断裂构造对岩浆侵入、火山活动及与其相关成矿作用的控制,并对区内典型矿床的控岩控矿构造条件作了论述。

... 庐枞盆地结晶基底的埋深呈明显的坳陷盆地形态, 显示了中生代以来经历的伸展坳陷过程(汤家富等, 2010 ...

2016

0.0

... 田晓峰等(2016)采用线性叠加方法, 基于长江航道内大容量气枪定点激发数据获得了可追踪至60km以远的Pg震相, 并开展了上地壳走时成像的初步研究 ...

... 对经相位加权叠加的记录截面进行2~8Hz带通滤波后发现, Pg震相可追踪的距离为80~96km, 与线性叠加方法(田晓峰等, 2016)相比可追踪距离大大提升 ...

... 最终拾取了上地壳初至波Pg震相912个, 比此前初步研究(田晓峰等, 2016)中的628个Pg震相数量增加了284个 ...

... , 1994), 得到震相拾取误差的均值为90~120ms, 与初步研究中采用经验性走时的误差赋值(田晓峰等, 2016)相比, 提升了震相拾取误差的精确度 ...

... 不同于传统的经验性选取初始模型的办法(田晓峰等, 2016), 本研究采用Malinowski等(2008)提出的多尺度反演网格迭代选取初始模型的方法 ...

2006

0.0

吴怡, 嘉世旭, 段永红, 等. 2006. 地震折射波法在郑州市西区浅层勘探中的应用[J]. 地震地质, 28(1): 84—92.

, JIA

Shi-xu

, DUAN

Yong-hong

, et al. 2006. The application of refraction method to shallow exploration of western Zhengzhou[J]. Seismology and Geology, 28(1): 84—92(in Chinese).

Seismic refraction method is tentatively used in the exploration of urban active faults where strong interference of surface waves exists and it is difficult to use seismic reflection survey. Original seismic refraction data are calculated and inversed by using time-terms, curve of differential time-distance and finite-difference tomography, to investigate the effect of the new technique in the exploration of urban active faults.In this paper, velocity structures and interface structures are obtained after the shallow seismic refraction data in the western segment of Xushui fault of western Zhengzhou are calculated and inversed by using the above-mentioned three calculation methods, and structural characteristics and depths of main geologic strata are got by integrating inversion results and features of seismic phases. The results of these three methods are similar, and they are confirmed by drilling data in the profile. The seismic refraction method can be used in the exploration of urban active faults.

1. Department of Engineering Survey, Earthquake Administration of Zhengzhou City, Zhengzhou 450007, China; 2. Geophysical Exploration Center, China Earthquake Administration, Zhengzhou 450002, China

在城市活断层勘探中,对于面波干扰大、地震反射波法难以开展工作的区域,可尝试利用地震折射波法进行探测,并对折射波法探测的原始记录采用时间项、差异时距曲线和有限差分成像等方法进行综合计算、分析,以探索折射波法在城市活断层勘探中的应用成效。文中针对郑州市须水断层西段浅层地震折射波法勘探记录,利用时间项、差异时距曲线和有限差分成像等计算方法,获取剖面速度结构与界面构造;综合震相特征、计算结果等资料确定主要地层的界面深度和构造特征,3种方法都取得了相近的结论。后又通过在测线上4个钻孔资料的验证,认为3种方法的计算结果与钻孔资料相吻合,说明折射波法勘探在城市活断层探测中的应用是可行的。

... 吴怡等, 2006 ...

2013

0.0

... 徐涛等, 2013 ...

2016

0.0

... 薛怀民等, 2016), 该区具有全段最深的基底, 可达约4 ...

... 薛怀民等, 2016) ...

2011

0.0

... 杨卓欣等, 2011) ...

2015

0.0

... 张明辉等, 2015) ...

2011

0.0

周涛发, 范裕, 袁峰, 等. 2011. 长江中下游成矿带火山岩盆地的成岩成矿作用[J]. 地质学报, 85(5): 712—730.

ZHOU

Tao-fa

, FAN

, YUAN

Feng

, et al. 2011. Petrogensis and metallogeny study of the volcanic basins in the Middle and Lower Yangtze metallogenic belt[J]. Acta Geologica Sinica, 85(5): 712—730(in Chinese).

The Middle-Lower Yangtze River Valley is one of the most important Cu-Fe polymetallic belts in China, in which occurs many volcanic basins, such as Li-Shu, Li-Yang, Ning-Wu, Fan-Chang, Lu-Zong, Huai-Ning and Jin-Niu volcanic basin. Compared with the uplift area in this region, the researches on the petrogenetic and metallogenetic in the volcanic basin are still poorly investigated. Basing on the summaries of the contributions of the previous researchers as well as our fundamental studies in recent years mainly on Lu-Zong basin and Ning-Wu basin, this paper discussed the geological characteristics, the temporal-spatial framework, geochemistry, geochronology of petrogenesis and mineralizations and metallogenetic model of the volcanic basins in the Middle-Lower Yangtze River metallogenetic belt. The chronological results of the igneous rocks suggests that the magmatic rocks in the volcanic basins formed in early Cretaceous (135~123Ma). The geochemical features of the volcanic rocks and the intrusive rocks in the volcanic basins indicate that their evolution, sources and the origin of the four formation volcanic rocks and the two epochs of intrusions are comparable. The source of the igneous rocks might be the metasomatic mantle, the formation of the metasomatic mantle was related to the subduction of the paleo-Pacific plate. The magma evolution underwent fractional crystallization and in the magma chamber and contamination during rising. Iron is the main mineralization occurred in the volcanic basins, which represented by the “porphyry iron deposits”. The “porphyry iron deposits” include a series of volcanic-subvolcanic hydrothermal deposits, sedimentary-reformed deposits, pyrite deposits, anhydrite deposits and alunite deposits. The geological and geochemiscal characteristics of these deposits indicated that their formation were closely related to the subvolcanic rocks (diorite porphyry) and diorite intrusions, and also controlled by the volcanic structures and the basal halites in the Triassic strata. The mineralization chronology shows all the porphyry iron deposits are “booming” formed around 130Ma in a short interval. This paper proposes a petrogenetic and metallogenetic model for the volcanic basins in the Middle and Lower Reaches of the Yangtze River area metallogenetic belt. The petrogenetic and metallogenetic in these volcanic basins is one part of Mesozoic tectono-magmatic-metallogenic event controlled by the geodynamic setting of eastern China in the Yanshanian period.

长江中下游成矿带是我国重要的铜铁多金属成矿带，其中发育溧水、溧阳、宁芜、繁昌、庐枞、怀宁和金牛盆地等火山岩盆地。与成矿带中断隆区相比，火山岩盆地内的成岩成矿作用研究仍显滞后。本文综合已有研究工作和资料，以庐枞盆地和宁芜盆地为主，探讨长江中下游地区火山岩盆地的地质特征、岩浆岩时空格架、地球化学特征及成矿作用和成矿模式等。长江中下游成矿带火山岩盆地内岩浆岩的年代学研究表明，各陆相火山岩盆地内岩浆岩均形成于早白垩世（135~123Ma），不同盆地内各旋回火山活动时间几乎相同，盆地中侵入岩的分期、岩性和成岩时代也大致可以对比。地球化学特征研究表明，盆地内早晚两旋回火山岩与两期侵入岩在岩浆起源、岩浆演化特征、岩石成因等方面一致，可以完全对应。岩浆源区为成分接近富集的交代地幔，交代地幔的形成与古板块的俯冲交代作用有关。岩浆演化经历了结晶分异作用和同化混染作用，岩浆结晶分异作用主要发生于深部岩浆房中。长江中下游成矿带火山岩盆地中成矿作用以铁矿化为主，产出以著名的“玢岩铁矿”矿床组合为特征的一系列不同类型的火山-次火山热液型和沉积改造型等铁矿床及硫铁矿、硬石膏和明矾石矿床。矿床地质地球化学特征研究表明，铁矿床和次火山岩（闪长玢岩）关系密切，其形成还受火山构造和基底膏盐层等控制和影响。成矿年代学研究证实不同玢岩型矿床的成矿时代基本一致，均为130Ma左右，盆地内铁成矿作用是在较短时间（1~2Ma）内集中“爆发式”形成的。综合火山岩盆地成岩成矿作用特征，本文建立了长江中下游成矿带火山岩盆地的成岩成矿模式，并认为火山岩盆地成岩成矿作用是中国东部中生代构造-岩浆-成矿系统演化的有机组成部分，受中国东部中生代地球动力学背景的制约。

... 研究区最西部的怀宁盆地紧邻大别造山带, 为继承式火山岩盆地, 是长江中下游地区形成最晚的火山盆地(周涛发等, 2011 ...

... 晚三叠世湖相沉积, 上覆早中侏罗世河湖相沉积(周涛发等, 2011 ...

... 岩浆地球化学研究显示, 怀宁盆地内的火山岩组成呈复合型, 即早期的火山岩属橄榄玄粗岩系列, 晚期的火山岩含钾钙量较高, 属于碱性系列(周涛发等, 2011 ...

... 周涛发等, 2011) ...

1969

0.0

... ²来判断, 其定义为(Bevington, 1969) ...

1988

0.0

... 而基于射线追踪的正演试错方法无法计算滑行波, 通常给出的是折射界面(Cerveny et al ...

1971

0.0

... 由于部分Pg波为沿着基底界面滑行产生的首波, 这种滑行波对界面形态十分敏感(Cerveny et al ...

... 由于滑行波仅对界面形态和界面处的速度值敏感(Cerveny et al ...

2007

0.0

... 近年来, 在陆上水体中激发大容量气枪震源(Chen et al ...

1986

0.0

... Hearn等(1986)提出可增加水平分层以更好地约束上覆速度, 利用直达波约束上覆层速度来约束时间项反演的建议 ...

1992

0.0

... 然而, Valenta等(2007)仍然建议研究中应结合包含首波因子算法(Hole et al ...

2009

0.0

... Magnani et al ...

2008

0.0

... 不同于传统的经验性选取初始模型的办法(田晓峰等, 2016), 本研究采用Malinowski等(2008)提出的多尺度反演网格迭代选取初始模型的方法 ...

... ²=1)的模型后, 对该模型进行一维平均或大尺度平滑成为一维模型, 以此作为反演的初始模型(Malinowski et al ...

1957

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... 时间项方法是传统上用来确定基底深度的一种有效方法, 能够利用首波走时反演沿界面的首波滑行速度和滑行界面的深度(Scheidegger et al ...

2007

0.0

... , 2014)及微弱信号处理提取(Schimmel et al ...

... 本研究使用基于相位加权的叠加方法(Schimmel et al ...

... , 2012)和相位加权叠加(图3c)(Schimmel et al ...

2018

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... She等(2018)利用主动源激发的面波信号, 获得了沿江主要成矿带浅部的S波波速异常 ...

2018

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... Tian等(2018)利用走时成像方法, 构建了区域尺度的上地壳三维精细结构 ...

2014

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... 为检验反演结果的稳定性和分辨能力, 本研究利用Zelt(1998)和Tian等(2014)提出的多尺度检测板相似度分析方法对结果进行稳定性检验和分辨分析 ...

... Tian et al ...

2007

0.0

... Valenta等(2007)指出, 为了保持反演过程的稳定, 正则化方法最终获得的模型受一定的平滑约束, 对于某些特殊构造难以精确成像, 同时提出了一种基于先验信息的三维时间项方法, 该方法能够快速地确定滑行界面的埋深 ...

... 然而, Valenta等(2007)仍然建议研究中应结合包含首波因子算法(Hole et al ...

... 5km/s速度等值线以上的介质视为不能被滑行波走时数据约束的盖层(Valenta et al ...

2012

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... , 2011, 2012 ...

... 为获得地壳深部的地震信号, 对20个固定激发点产生的数据进行线性叠加(图3b)(Wang et al ...

2011

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... Wang et al ...

2014

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... Yang et al ...

1998

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... 2 初至波走时成像方法本研究首先采用正则化反演的走时成像方法(Zelt et al ...

... 反演中, 数据协方差矩阵C_d是一个对角矩阵, 其对角元素为Pg震相的到时拾取误差的平方值(Zelt et al ...

... C_v的定义和操作类似, 详见Zelt等(1998)的原文 ...

... 然而, 由于地震宽角反射/折射数据反演具有强烈的非线性, 每一步迭代过程中的阻尼因子均不同, 本文所用的初至波走时成像方法在选择阻尼因子时一般采用尝试法(Zelt et al ...

... 为检验反演结果的稳定性和分辨能力, 本研究利用Zelt(1998)和Tian等(2014)提出的多尺度检测板相似度分析方法对结果进行稳定性检验和分辨分析 ...

... 为了将检测板恢复试验的结果量化, Zelt(1998)提出以检测板恢复相似度R作为模型分辨的参考, 相似度R的定义为 ...

2006

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... 该阈值在已开展的走时成像研究中被多次应用(Zelt et al ...

1998

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... 该分辨率的定义中, Zelt(1998)指出单个棋盘格内的检测板相似度为0 ...

1994

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... 利用互相关方法获取震相的拾取误差(Zelt et al ...

1992

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... 本研究借鉴上述研究的经验和建议, 利用前述层析成像的结果(图6a)给出精确的基底上覆盖层的速度, 并利用基于射线反演的方法, 将初至波到时中的372个基底滑行波单独选出, 利用能够实现滑行波射线追踪和阻尼最小二乘反演方法的RAYINVR软件包进行反演(Zelt et al ...

... 射线反演方法(RAYINVR)可采用不规则的网格进行参数化(Zelt et al ...

... Zelt et al ...

... 5则可视为已获得了足够的分辨(Zelt et al ...

2016

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... Zeng et al ...

2003

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... 在正则化走时反演中, 由于阻尼因子和平滑参数共同约束反演, 一般采用L曲线法选取阻尼因子和平滑参数(Zhang et al ...