地球化学小波分析在火山旋回韵律厘定中的应用 --以埃塞俄比亚北部施瑞地区为例

韩世礼^{1, 2}，张术根^{1, 2}，柳建新^{1, 2}，丁俊^{1, 2}，张文山^{1, 2, 3}，朱思才³

(1. 中南大学 有色金属成矿预测教育部重点实验室，湖南 长沙，410083；
2. 中南大学 地球科学与信息物理学院，湖南 长沙，410083；
3. 中色金地资源科技有限公司，北京，100012)

摘 要：以埃塞俄比亚北部施瑞地区变火山岩系为典型实例，阐述变火山岩系火山旋回的岩性岩相特征，并在此基础上探讨利用地球化学含量小波分析识别火山旋回韵律的技术与方法。通过地质地球化学剖面对比分析，选择具有代表性的地球化学元素Si和Fe+Mg含量作为分析对象，选择db5小波基进行三尺度小波分解与重构。提取有关旋回韵律演化的信息，综合对比各地质剖面的空间分布特征，变火山岩系共划分出6个旋回15个韵律。研究结果表明：经小波处理后的地球化学含量有效去除了局部噪音干扰；小波分析在火山旋回厘定中不仅可有效划分区域火山旋回，而且可有效判别旋回中的韵律。

关键词：小波分析；地球化学；火山旋回韵律；埃塞俄比亚施瑞地区

Geochemical wavelet analysis application in discrimination of volcanic cycle and rhythm: An example from Shire region in northern Ethiopia

HAN Shi-li^{1, 2}, ZHANG Shu-gen^{1, 2}, LIU Jian-xin^{1, 2}, DING Jun^{1, 2}, ZHANG Wen-shan^{1, 2, 3}, ZHU Si-cai³

(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education,
Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
3. Beijing Donia Resources Co. Ltd, Beijing 100012, China)

Abstract:Taking the meta-volcanics in Shire region of Ethiopia northern as a typical instance, the lithology lithofacies characteristics of the meta-volcanics cycle were compound, and the technology and method were discussed to identify volcanic cycle and rhythm by using geochemical data. Through the geological and geochemical section analysis, this method selects the representative geochemical elements Si and Fe+Mg content as analysis object and db5 wavelet bases for the three-scale after wavelet decomposition and reconstruction. Synthetically comparing the spatial distribution characteristics of the geological section, the meta-volcanics were divided into 6 cycles and 15 rhythm. The results show that wavelet processing, the geochemical data effectively remove the local noise interference and extract the information about cycle and rhythm. The wavelet analysis plays a unique function and effect in discrimination of volcano cycle, i.e. it not only effectively divides the regional volcanic cycle, but also validly identifies the rhythm inside volcanic cycle.

Key words:wavelet analysis; geochemistry; volcanic cycle and rhythm; Shire in Ethiopia