应用二维经验模分解(BEMD)提取反应鲁西地幔隆陷重力异常

BEMD and its Application in Extraction of Gravity Anomaly Originated from Mantle Swell and Sags within the Western Shandong Uplift, Eastern China

摘要: 将二维EMD方法应用于鲁西地块重力数据分解，获取反映研究区不同尺度深部地幔隆陷及其与金矿化空间分布关系的IMF₄和IMF₃重力分量图像。IMF₄低通滤波重力分量图像显示鲁西地块存在1处一级区域性地幔隆起，临沂幔隆(I_UY)和两处一级区域性地幔凹陷，平邑幔陷(I_DP)和莱芜幔陷(I_DL)。几乎所有金矿床及其相关的中生代火成岩体(侵入岩和火山岩)皆沿这种区域性幔隆或幔陷的边缘分布。IMF₃带通滤波重力分量图像，揭示在一级区域性地幔隆陷的基础上发育的二级区域性地幔隆陷特征。在整个研究区这种二级区域性幔隆和幔陷呈带状相间分布。在研究区东部，临沂–沂南–沂水幔隆西侧分布有相同展布方向和近似规模的孟良崮–棱背岭–沂山–唐吾幔陷，在其南东侧发育临沭–莒南幔陷。在研究区中西部，分布4对呈北西向分布的地幔隆陷。自南至北，依次为张庄–滕州幔陷；向城–石井–水泉–南辛幔隆；罗庄–郑城–四海山幔陷；临沂–费县–平邑–泗水幔隆；蒙山–宫里–泰安幔陷；蒙阴–新泰–徂徕–柳埠–济南幔隆；雁翎关–跺庄幔陷；辛庄–腰关–阎家峪幔隆。研究区构造线的分布与二级幔隆和幔陷的展布方向具有高度一致性。金矿床及其相关的中生代岩浆岩(侵入岩和火山岩)绝大多数分布于二级幔隆区或其边缘。业已表明，中生代太平洋板块向欧亚板块俯冲导致的郯庐断裂大规模的左行平移引起鲁西二级区域性地幔隆陷，二级地幔隆陷导致的拉张和挤压作用引起的构造岩浆活动构成中生代金–铜金成矿的有利地质背景，发育于二级地幔隆起及其边缘的构造岩浆岩带是找寻Au(Ag)、Cu等矿床的远景地段。

Abstract: Bi-dimensional empirical mode decomposition (BEMD) is effectively used to handle gravity sig-nals for the western Shandong uplift block. This yielded two two-dimensional intrinsic mode function (IMF) images that depict two layers of mantle swells and sags with different size and their spatial distribution relationships to various gold deposits and related igneous bodies re-spectively. A low-pass filtered image (IMF₄) depicts one the first class of mantle swell, Linyi one (I_UY) and two the first class of mantle sags, Pingyi one (I_DP) and Laiwu one (I_DL). Almost all Meso-zoic intrusions and gold deposits associated with the intrusions are distributed at the edges of both the mantle swells and the mantle sags. A band-pass filtered IMF3 image depicts the spatial distributions of the second class of mantle swells and sags developed on the basis of the first class of mantle swell and sags. The second class of the mantle swells and sags occurs in belt in whole area. In the eastern part of the study area, the Linyi - Yinan - Yishui mantle swell belt is distributed in NNE orientation along the Yishu fault belt and there are two mantle sags on the both side of the mantle, one being the Menglianggu - Lengbeiling - Yishan - Tangwu mantle sag on its northwestern side and another the Linshu - Junan mantle sag on its southeastern side, which are distributed in the same orientation with the mantle swell belt. In middle-west part of the study area, there are four couples of mantle sags and swells which are distributed in NW orientation. From south toward north, they are in order the Zhangzhuang - Tengzhou mantle sag, Xiangcheng - Shijing - Shuiquang - Nanxin mantle swell; Luozhuang - Zhengcheng - Sihaishan mantle sag, Linyi - Feixian - Pingyi - Sishui mantle swell; Mengshan - Gongli - Taian mantle sag, Mengyin - Xintai - Zulai - Liubu - Jinan mantle swell; Yanlingguan - Duozhuang sag, and Xinz-huang - Yaoguan - Yanjiayu swell. The tectonic lineaments are distributed in the same orienta-tion with the mantle swells and sags. Almost all the Mesozoic intrusions and gold deposits asso-ciated with the intrusions are located within the mantle swells and/or at the edges of them. It has been illustrated that subduction of the Pacific plate beneath the Euro-Asia continent in the Mesozoic era might trigger the Tanlu Fault moved in sinistral strike-slip on a large scale to pro-duce the second class of mantle swells and sags. The mantle swells might be tectonically an ex-tensional area where the magma rocks are well developed to produce gold and/or copper-gold deposits associated with the magma activities. Thus, these magma rock areas are favorable areas for prospecting gold and copper-gold deposits.