摘要
为揭示沂沭断裂带深部结构及发生-发展过程,查清断裂切割深度及对岩石圈地幔的破坏,探讨沂沭断裂带的构造组合样式、运动方式、地壳稳定性及其对资源环境的约束作用,研究团队于2019年在沂沭断裂带南段沂南-莒县附近布设了一条长约60 km的深反射地震剖面,系统采集了沂沭断裂带和两侧地块的地震数据,对沂沭断裂带深部岩石圈精细结构进行了解剖。结果显示,该区岩石圈结构在横向上表现为以沂沭断裂带为界的块状结构特征,地壳厚度约30.8~39.5 km;莫霍面总体呈西浅东深态势,并被西倾的沂水-汤头断裂(F2)和昌邑-大店断裂(F4)错断,垂直落差达10.5 km。与浅部"两堑夹一垒"的构造组合样式不同的是,沂沭断裂带在深部剖面上表现为由沂水-汤头断裂(F2)和昌邑-大店断裂(F4)向上延伸与分叉散开的多条断裂组成"双枝状"构造组合样式。断裂带内被断层切割的界面反射波多呈向上的拱弧形,其构造形迹具有伸展、挤压和走滑并存的特征,推断这些界面为层间滑脱构造,它们指示了沂沭断裂带"多层滑移"构造运动方式。该断裂带不仅切穿了近地表、壳内地质界面,F2、F4断裂还向下切割莫霍面,深入岩石圈地幔,是深达地幔的深大断裂构造带,为地幔热物质的上涌提供了通道,对中生代的岩浆活动和内生成矿具有控制作用。地震剖面西端的铜井金矿成矿与沿F2断裂上侵的铜井杂岩体关系密切;剖面东端的火山机构保存完整,没有明显构造破坏痕迹,据此认为沂沭断裂带左行走滑主要发生在早白垩世青山期以前,其后水平滑移量应不大。从区域地质分布及地震反演结果看,昌邑-大店断裂(F4)明显将山东省分割为鲁西和鲁东两个地质构造单元,因此将其作为区域地质构造分界线是合理的。本项研究结果进一步加深了沂沭断裂带深、浅部结构的认识,为分析研究沂沭断裂带的深部过程和浅部构造响应及对资源环境的影响提供了资料约束。
Seismic data were systematically collected from a deep reflection seismic profile about 60 km long set up near the Yinan-Juxian in the southern segment of the Yishu fault zone(YSFZ)to dissect the fine structure of the lithosphere of the YSFZ and the blocks on both sides.The objectives of this study were to(i)reveal the deep structure and occurrence-development process of the YSFZ;(ii)expose the cutting depth of the fault and the damage to the lithospheric mantle;(iii)explore interpretation of the YSFZ tectonic combination style;and(iv)assess crustal stability and its constraints on resources and environment.The results show that the lithospheric structure of this area is laterally characterized by a massive structure bounded by the YSFZ and the crustal thickness of this area is about 30.8~39.5 km.The Moho surface is generally shallow in the west and deep in the east,and it is broken by the Yishui-Tangtou fault(F2)and Changyi-Dadian fault(F4)that lean to the west,with a vertical drop of 10.5 km.Different from the shallow structural combination pattern of"two grabens sandwiched with one horst",the YSFZ appears as a"double branched"structural combination pattern consisting of multiple faults extending upward and bifurcating from the Yishui-Tangtou fault(F2)and the Changyi-Dadian fault(F4)on the section.The reflected waves of the interface cut by the fault are mostly upward arcs,and the structural traces have the characteristics of extension,compression and strike-slip.It is inferred that these interfaces are interlayer slip structures,which indicate the"multi-layer slip"tectonic movement mode in the YSFZ.The YSFZ cuts the geological interface near the surface and the inner crust.The F2 and F4 faults cut the Moho surface downwards and penetrate into the lithospheric mantle.The YSFZ is a deep faulted structural zone reaching the mantle and provides a channel for the upwelling of hot mantle materials and controlling the Mesozoic magmatism and endogenetic mineralization.The mineralization of Tongjing gold deposit at the western end of the seismic section is closely related to the Tongjing complex intrusion along the F2 fault;the volcanic structure at the eastern end of the profile is well preserved without obvious traces of structural damage.Therefore,it is considered that the left lateral strike slip of the YSFZ occurred mainly before the early Cretaceous Qingshan period,and the post horizontal slip should be small.According to the regional geological distribution and seismic inversion results,Changyi-Dadian fault(F4)obviously divides Shandong Province into two geological structural units,i.e.West Shandong and East Shandong.Therefore,it is reasonable to consider it as the boundary of regional geological structure.The results of this study further deepen the understanding of the deep and shallow structure of the YSFZ,and provide data constraints for the analysis and study of the deep process and shallow structure response of the YSFZ and its impact on the resource environment.
作者
张尚坤
罗文强
于学峰
田京祥
唐璐璐
陈军
杨斌
杜圣贤
刘凤臣
仵康林
ZHANG Shangkun;LUO Wenqiang;YU Xuefeng;TIAN Jingxiang;TANG Lulu;CHEN Jun;YANG Bin;DU Shengxian;LIU Fengchen;WU Kanglin(Key Laboratory of Gold Mineralization Processes and Resources Utilization,Ministryof Land and Resources,Key Laboratory of Metallogenic Process and Resource Utilization of Metallic Minerals of Shandong Province,Shandong Institute of Geological Sciences,J inan,Shandong 250013,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2021年第11期3192-3204,共13页
Acta Geologica Sinica
基金
山东省2017重点研发计划(鲁科字[2017]88号)“深地资源勘查开采”专项“沂沭断裂带深部结构及对资源环境的影响”(编号2017CXGC1602)项目资助的成果。
关键词
深反射地震剖面
沂沭断裂带
岩石圈结构
双枝状构造
多层滑移
deep reflection seismic profile
Yishu fault zone
lithospheric structure
double branch structure
multi-layer slip
