摘要
不同于华北克拉通东部普遍存在的NE走向断层,鲁西地块广泛发育一组特征明显的NW走向断层,包括非控盆断层和控盆断层两类。前者位于鲁西地块最南部,倾角相对较陡,错开了古生界及以下地层,下盘太古宇中发育韧性剪切带,断层碎裂岩指示断层存在多期活动;后者位于非控盆断层以北,除蒙山断层外韧性剪切带不发育,倾角相对较缓,控制了中生代以来的沉积。磷灰石/锆石裂变径迹证据分析得出NW走向断层的活动存在差异。断层上、下盘样品磷灰石裂变径迹表观年龄在在67±5~35±2Ma之间,径迹直方图表明样品在冷却过程中没有受到热扰动。通过平均径迹长度-年龄(或香蕉图)图、单颗粒峰值年龄、径迹年龄谱模式以及热史反演模拟综合分析来约束断层的活动时间,结果表明非控盆断层可能在早侏罗世约184Ma开始活动,之后在晚白垩世80~75Ma以及新生代~61Ma和51~43Ma活动,43Ma之后不再活动。控盆断层活动时间稍晚,于早白垩世约141Ma、晚白垩世80~75Ma活动,新生代活动时间为约61Ma、49~42Ma以及36~32Ma。总体上,NW走向断层由早到晚由南向北发育,非控盆断层活动时间早、结束早;控盆断层活动晚、结束晚,并控制了凹陷的向北发育。中生代以来区域构造应力场的变化和郯庐断裂带的走滑作用是导致两类NW走向断层差异演化的根本原因,在深部则受控于晚三叠世以来华北、扬子板块陆陆碰撞和古太平洋板块俯冲方向和速度的改变。印支期后挤压到伸展的转变,加上郯庐断裂带的左行走滑,使靠近华北克拉通南缘的前端NW走向断层首先发育,因倾角较大故不控制盆地发育;向北的后端相对伸展,成为控盆断层,后经早白垩世约141Ma期间的伸展、晚白垩世末80~75Ma和新生代的发育断层最终成型。NW走向断层的这种大致向北迁移的规律,隐示华北克拉通破坏可能始于早侏罗世或晚侏罗世,且由南向北逐渐拆沉。
Unlike the North China Craton,the eastern part of which commonly contains NE-trending faults,the Luxi Block hosts one group of well-developed NW-trending faults with obvious geological features, including non-basin-controlled faults and basin-controlled faults.The former is located in the south end of the Luxi Block,with relatively large dipping,and cuts through the Paleozoic and underlying strata. Ductile shear zone occurs in the lower Archaean footwall,with faulting fragments indicating multiple activities.The latter located in the north of the non-basin-controlled faults,except the Mengshan fault, has underdeveloped ductile shearing zone and relatively flat dip,which controls the sedimentation since the Mesozoic.Apatite/zircon fission track analysis show that there existed some differences in activity of the NW-trending faults.The apparent ages of apatite fission track for the samples from hanging wall and footwall are 67+5Ma and 35+2Ma,respectively,and the track histogram shows that the samples were not subject to thermal disturbances during the cooling process.The activity time of the faults is restrained using the average track length-age (or banana diagram),single grain peak age,track age spectrum pattern and thermal history inversion simulation.The results show that the non-basin-controlled faults might start activity in the Early Jurassic of about 184Ma,and continued to be active in the Late Cretaceous 80~75Ma and the Cenozoic ca.61Ma and 51~43Ma,and might cease after 43Ma.The basin-controlled faults started active relatively late,probably in Early Cretaceous ca.141Ma,Late Cretaceous 80~75Ma,and was active in about 61Ma,49~42Ma and 36~32Ma during the Cenozoic period.In general,the NW-trending faults developed chronologically from south to north.The non-basin-controlled faults were active early but ceased early;while the basin-controlled faults were active late but ceased later and controlled northward development of the depression.Changing of regional tectonic stress field and strike-slipping of the Tan-Lu fault zone since the Mesozoic was the fundamental causes for the evolution divergence of two types of NW faults.Deep part of the faults was controlled by continent-content collision of North China and Yangtze plates in the Late Triassic,as well as direction and speed change of paleo-Pacific plate subduction.The Indosinian transition from compression to extension,coupled with the sinistral strike-slipping of the Tanlu fault zone,gave the top priority to the development of NW-trending faults near the southern margin of the North China Craton.Because the large dip angle failed to control the development of the basin,the faults extended relatively toward north end,forming basin-controlled faults.After extension in the Early Cretaceous (ca.141Ma),the faults finally gradually took a shape at end of Late Cretaceous (ca.80~ 75Ma)and in the Cenozoic.The generally northward migration of the NW-trending faults suggests that destruction of the North China Craton may initiate in the Early Jurassic or Late Jurassic and delaminated gradually from south to north.
作者
李理
钟大赉
陈霞飞
陈衍
LI Li;ZHONG Dailai;CHEN Xiafei;CHEN Yan(School ofGeosciences,China University of Petroleum,Qingdao,266580;Laboratory for Marine Mineral Resources,Qingdao National laboratory for Marine Science and Technology,Qingdao,266071;Institute of the Geology and Geophysics,Chinese Academy of Sciences,Beijing ,100029)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2018年第3期413-436,共24页
Acta Geologica Sinica
基金
国家自然科学基金(41672193)资助的成果
