基于地球物理反演结果对沂沭断裂带中段深部结构再认识
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本文为山东省自然科学基金面上资助项目(编号:ZR2020MD039)和山东省地质勘查项目(编号:鲁勘字(2019)13号)的成果


Understanding of deep structure of Yishu fault zone based on three- dimensional gravity inversion model
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    摘要:

    沂沭断裂带为郯庐断裂带山东段的大断裂,其深度切穿莫霍面,把鲁中造山带与苏鲁造山带隔开,断裂带的活动情况影响山东地区大地构造的稳定性。以往的工作多集中在地表或近地表地质要素的调查和研究,局部也开展了一些地球物理探测工作,大多以剖面为主,对区内地质构造的认识比较局限。本文收集沂沭断裂带约14600 km2范围的区域重力数据,并对其进行了定性解释和三维定量反演,获得了区内地下30 km内的相对密度分布。综合研究了从诸葛镇到五连金矿的精测剖面,其中包括重力、磁法和大地电磁3种方法。由此得到以下几点结果:①揭示了区内东部地下存在一条巨大的隐伏隆起构造,深度约2 km到10 km,从南南西方向延伸到北北东,有3个局部核心区:分别是石桥子镇往西南约30 km范围、由桑园镇、五莲县金矿及许孟镇三者之间的区域、以湖头镇为中心向北向南各延伸约30 km范围。②地表观察的断裂F1和F2比由反演的相对密度确定的断裂F′1和F′2向东偏移,而且北部偏移比南部更大。③重力、磁法、大地电磁测深综合剖面S1—S2研究表明,沂沭断裂带北段内岩矿石具有较低的相对密度、较低的磁性和较低的电阻率特征,意味着断裂带在北部具有张性特点。综上所述,研究区内东部上地壳内存在隐伏隆起构造,昌邑—大店断裂和安丘—莒县断裂在北部具有张性断裂特征,在南部具有挤压特征,莒县以南小地震方式释放部分应力。

    Abstract:

    Yishu Fault Zone is part of Tanlu Fault Zone in the Shandong Province. It cuts through the Moho surface and separates the central Shandong orogenic belt from the Sulu orogenic belt. The activity of the fault zone determines the tectonic stability of Shandong area. In the past, most of the work focused on the investigation and research of surface or near surface geological elements, and some geophysical exploration work was also carried out in some parts, mostly focusing on sections, and the understanding of the geological structure in the area is relatively limited. In this paper, the regional gravity data of about 14600 square kilometers in the Yishu Fault Zone are collected, and the three- dimensional inversion is carried out. The relative density distribution within 0~30 km underground in the area is obtained. The precise survey sections from Zhuge Town to Wulian gold deposit are comprehensively studied, including gravity, magnetic method and magnetotelluric method. The following results are obtained: ① It is revealed that there is a huge hidden uplift structure underground in the east of the area, with a depth of about 2 km to 10 km, extending from south- west to north- east, and there are three local core areas: about 30 km from Shiqiaozi Town to southwest, between Sangyuan Town, Wulian gold deposit and Xumeng Town, and about 30 km from north to south centered on Hutou Town. ② Faults F1 and F2 observed on the surface are shifted to the right than faults F′1 and F′2 determined by the inverted relative density, and the migration in the north area is greater than that in the south area. ③ The comprehensive profile study of gravity, magnetic method and magnetotelluric sounding shows that the rocks and ores in the north section of Yishu Fault Zone have the characteristics of low relative density, low magnetism and low resistivity, which means that the fault zone has tensile characteristics in the north. To sum up, there are concealed uplift structures in the eastern upper crust of the study area. Changyi—Dadian fault and Anqiu—Juxian fault have tensile fault characteristics in the north and compressive characteristics in the south. Small earthquakes occur frequently in the south of Juxian.

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朱裕振,强建科,李强,沈立军,贾金荣.2023.基于地球物理反演结果对沂沭断裂带中段深部结构再认识[J].地质论评,69(1):113-122,[DOI].
ZHU Yuzhen, QIANG Jianke, LI Qiang, SHEN Lijun, JIA Jinrong.2023. Understanding of deep structure of Yishu fault zone based on three- dimensional gravity inversion model[J]. Geological Review,69(1):113-122.

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  • 收稿日期:2022-03-21
  • 最后修改日期:2022-07-16
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  • 在线发布日期: 2023-01-20
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