福州盆地及其周围地区地壳深部结构与构造的初步研究

1986-1988年,福建省地震局在福州盆地及其周围地区完成了五条地震测深剖面:宁德-永春剖面;洪懒-宁德剖面;莲峰-福州（尚干）剖面;南平-永泰-平潭非纵剖面;并在宁德-古田-嵩口首次试验扇形剖面观测系统,结果表明,扇形剖面对确定断裂是有效的. 根据对地震波走时的正、反演计算,用理论地震图和射线追踪方法进一步修改和完善,得到了福州盆地及其周围地区地壳深部为高、低速相间的速度分布特征.地壳介质速度为6.40km/s,在中地壳普遍发育一层速度为5.80-5.90 km/s、厚度约5.0 km的低速层.Moho面深度30-33 km,福州盆地为一Moho面隆起区,隆起幅度达3.0 km.北西向断裂发育,其中,闽江断裂在纵剖面和扇形剖面均有明显的反映,并切割到Moho面2.0-3.0 km. 反射波谱频方法计算得到福州盆地地壳Q值仅120-150,比邻近地区明显偏低,中地壳低速层Q值为40-80,是一典型的低速-高导-低Q（高衰减）结构层,此层上界面埋深14-15 km,与居里面埋深较一致.这些结果为福州地区的地热资源远景预测和开发提供了地壳深部结构和某些地球物理场背景.     

中地壳的水和水岩相互作用实验及其地球物理涵义

本文重点报道了高温高压下流体与流体-岩石相互作用实验结果,提供了中地壳条件下流体性质和水岩反应速率数据.这些数据有助于理解中地壳的一些地球物理现象.作者进行了25℃~435℃和22~39 MPa条件下水-岩相互作用反应动力学实验.同时,研究水在近临界区至超临界区的性质.一般地说,中地壳大致位于10(15)至25 km的深度范围.各地的地壳厚度不同,但是中地壳高导-低速层的深度范围十分相似.中地壳的顶界温度处于300℃,底界大致为450℃范围,压力高达200 MPa以上.流体-岩石相互作用实验表明:硅酸盐矿物和岩石的硅最大溶解速率出现在300℃~400℃.此时,硅酸盐矿物格架解体.通常,地壳里普遍存在水、流体.地壳构造活动导致断裂空隙、减压、流体流动.这时,有可能导致中地壳处于300℃~450℃流体的压力减低,由超临界区进入临界态、亚临界态.这会引发强烈流动的水与岩石相互作用.溶解反应导致岩层的硅淋失,硅的强烈淋失又会导致硅酸盐矿物格架解体,岩石崩塌.同时,进一步促进流体的流动.实验表明300℃~400℃下的强烈水岩相互作用促进了岩石破坏,并有可能影响岩层的地球物理性质,如高导层出现.另外,实验和理论研究表明处于300℃~400℃流体具有高电导率性质.这些水岩相互作用会使中地壳出现高导-低速层.     

福州盆地及其周围地区地壳深部结构与构造的初步研究

1986—1988年,福建省地震局在福州盆地及其周围地区完成了五条地震测深剖面:宁德—永春剖面;洪懒—宁德剖面;莲峰—福州（尚干）剖面;南平—永泰—平潭非纵剖面;并在宁德—古田—嵩口首次试验扇形剖面观测系统,结果表明,扇形剖面对确定断裂是有效的. 根据对地震波走时的正、反演计算,用理论地震图和射线追踪方法进一步修改和完善,得到了福州盆地及其周围地区地壳深部为高、低速相间的速度分布特征.地壳介质速度为6.40km/s,在中地壳普遍发育一层速度为5.80—5.90 km/s、厚度约5.0 km的低速层.Moho面深度30—33 km,福州盆地为一Moho面隆起区,隆起幅度达3.0 km.北西向断裂发育,其中,闽江断裂在纵剖面和扇形剖面均有明显的反映,并切割到Moho面2.0—3.0 km. 反射波谱频方法计算得到福州盆地地壳Q值仅120—150,比邻近地区明显偏低,中地壳低速层Q值为40—80,是一典型的低速—高导—低Q（高衰减）结构层,此层上界面埋深14—15 km,与居里面埋深较一致.这些结果为福州地区的地热资源远景预测和开发提供了地壳深部结构和某些地球物理场背景.     

湖北襄樊—福建罗源的大地电磁测量与地壳上地幔电性特征研究

湖北襄樊—福建罗源一千多公里的剖面上作了23个大地电磁测深点。该剖面穿过不同的地质构造单元。 大地电磁测深的结果清楚地反映了剖面内地壳和上地幔的电性结构特征。例如构造单元的形态、边界、断层位置、地壳和上地幔的高导层发育情况等。结果对于了解该区的深部构造背景、探讨深浅构造之间的关系提供了有益信息     

也谈地壳内第二深度空间石油、天然气的形成及勘探前景

在当前国内油气供需紧张的严峻形势下,开展"第二深度空间"的油气勘探"势在必行",也是"当务之急"."第二深度空间"的油气勘探需解决3个问题.一是油气无机成因的地球化学证据.原油、沥青、干酪根的Pb,Sr,Nd同位素示踪、原油中异常高含量的金属微量元素、原油中有机硅化合物的发现等均表明原油可以由无机反应而生成.二是油气无机成因论是可以指导油气勘探的.油气的分布与中地壳的低速、高导层的耦合表明有成因关系,中地壳的低速、高导层是油气的发生器,也是初始储层,据此可以对油气田进行预测.柴达木盆地昆北花岗岩油田的发现是一典型案例.三是"第二深度空间"的油气勘探需要地球物理方法和技术的支撑.目前第4代采集处理新理论、新方法业已提出.地球物理学家已经把深部勘探的新方法、新技术提到议事日程.总之,"第二深度空间"的油气勘探是有理论依据的,是可能的,是可操作的.发现大型、超大型油气田指日可待.     

汶川大地震与中地壳低速、高导层的成因关系初探

四川汶川大地震给人们留下诸多困惑:大地震究竟是如何发生的,大地震能否避免?本文根据松潘--甘孜褶皱带的深部地壳构造特征表明:松潘--甘孜褶皱带的茂县(1933年)、松潘--平武(1976年)、汶川(2008年)大地震震源深度与中地壳低速、高导层深度大体一致,可能成因上相关.历史上一些大地震如银川地震、海原地震、渭南地震、海城地震、唐山地震等也均与中地壳低速、高导层有关,这一切均可能与地球排气作用有关.而通过地震、森林大火、油气资源的一体化勘查,可查明地震可能发生的区域.通过油气的勘查、开发、排放,可有效减少地震发生的可能性.     

Neogene palynological assemblages in the west slope of Songliao Basin and their geological implications

Abundant palynological fossils are found from the drill core in the west slope of Songliao Basin, the first full coring borehole that drilled throughout the Neogene. Two Palynological assemblages are recognized according to their vertical distributions, i.e., the late early Miocene–middle Miocene assemblage from the Da'an Formation named as Caryapollenites simplex-Momipites coryloides-Celtispollenites sp.-Tsugaepollenites igniculus, and the late Miocene-early Pliocene assemblage from the Taikang Formation named as Artemisiaepollenites minor-Betulaceoipollenites sp.-Carpinipites sp.-Polypodiaceaesporites sp. On the basis of the composition of each assemblage, we infer that the climate was warm-temperate to sub-tropic during the late early Miocene–middle Miocene and the vegetation was mainly deciduous broadleaved forest and subordinate coniferous and broad-leaved mixed forest with few understory ferns, and probably some shallow fresh water wetlands. The climate then turned cooler and drier in the late Miocene–early Pliocene, represented by the development of xerophytic herbs and temperate plants, although the canopy of the forest remained relatively stable. The results significantly improve the understanding of the Cenozoic palynostratigraphy in the Songliao Basin, and provide new data for both stratigraphical correlation and paleovegetational and paleoclimatical analysis in adjacent area.     

Microfossils and molecular records in oil shales of the Songliao Basin and implications for paleo-depositional environment

Several oil shale beds, over 10 m thick, occur at the base of the first member of the Upper Cretaceous Qingshankou Formation (K2qn1) in the Songliao Basin. They act both as excellent source rocks for conventional oil and as potential oil deposit for shale oil production. Here we combine micropaleon-tology with organic geochemistry to investigate the paleo-depositional environment and organic source characteristics of the oil shales and black shales. Our results indicate that algal remains are dominant micro...     

Crustal reflection structure in the uplifting zone of Songliao Basin and disconnecting Moho interface

Songliao Basin is one of the most important bases for oil-gas resources of China. Therefore, the mecha-nism of petroleum occurrence and basin dynamics have been paid much attention to by geo-scientists all the time. With multi-phase tectonic movements en-dured by the basin, its tectonic pattern is very complex. Thereinto, three faults, that is, western Neijiang fault(NNE25), eastern Yilan-Yitong fault (NNE30) and Sunwu-Shuangliao fault, extend along south-north direction and cut Songliao…     

Sedimentary filling and sequence structure dominated by T-R cycles of the Nenjiang Formation in the Songliao Basin

The Nenjiang Formation in the Songliao Basin is a symmetrical sequence of progradation-retrogradation,and is formed in the transgression cycle and regression cycle(T-R cycles)of the base level of deposition.We analyzed the drilling,well logging,core data,and seismic profiles of basin level,and by using the sequence stratigraphy,identified one secondary sequence boundary,two third-order sequence boundaries,and eight fourth-order sequence boundaries in the Nenjiang Formation.These eleven sequence boundaries can be divided into structural unconformity,depositional unconformity,flooding surface,and forced regression surface.Therefore the Nenjiang Formation can be subdivided into one secondary sequence,three third-order sequences,and ten fourth-order sequences.We have restored the sedimentary filling evolution within the stratigraphic framework of fourth-order sequences in the Nenjiang Formation.The sedimentary period of the first member of the Nenjiang Formation was corresponded to the global transgression period,which is also the development period of transgression cycle(T cycle),when the lake basin had the largest scope and deepest sedimentary water,the SB07(the maximum flooding surface)was formed on the top of strata during this period;covering above the SB07,there developed a set of condensation layer-oil shale,which is distributed in the whole basin and is the important source bed and regional cover.Therefore,a retrogradation sequence was formed in the T cycle of the first member of the Nenjiang Formation,characterized by the retrograding delta at a low angle.The delta has a giant front,a small plain,and many underwater distributary channels.Meanwhile,large gravity flow channels and sublacustrine fans are developed in the front of the delta.During the depositional period of the second member of the Nenjiang Formation,the R cycle began to develop due to the compression of the pacific tectonic domain;the source direction rotated 90°along with the eastern uplifting of the basin,and formed a series of east-west prograded and forced retrogradations.The prograding delta at high angel was developed in the interior of the sequence;the delta had a small front,a giant plain,and fewer underwater distributary channels,with the collapse at the foreslope,forming a series of slump fans.The slump fans can be divided into three types:discrete type,superimposed type,and fluid type.We built a whole"triad model"of the slump fan.Pointed out that the sequence of forced retrogradation formed by R cycle is a good structural mark of basin optimization,and rejected the viewpoint of"transgression"in the Nenjiang Formation of the Songliao Basin.     

松辽盆地东缘域地壳结构及其地质意义:深反射地震

松辽盆地东缘域位于松嫩—张广才岭微板块东部.自晚古生代以来该域经历了西拉木伦河缝合带闭合产生的北向挤压作用、蒙古—鄂霍茨克洋自西向东剪刀叉式闭合对其东侧东南侧产生的挤压作用以及西太平洋板块西向变向俯冲产生的挤压作用等区域构造应力场影响,从而产生了复杂的地壳变动.该东缘域的地壳结构与松辽盆地地壳是否具有相近的结构特点,这是至今未被研究的内容.在Songliao Drep研究中已经用深反射地震手段得到松辽盆地地壳结构的一组新认识.这些认识在其东缘域是否还成立,也需要用同样精度的手段予以研究.另外,莫霍界面的宏观特征与微观（内部）特征,从松辽盆地到其东缘域有什么样的变化,其形成机理是什么,也需要进一步研究.为了回答这些科学问题,从哈尔滨西至尚志市附近实施了一条东西向约150 km长的深反射地震剖面.通过研究发现东缘域与松辽盆地基底地壳具有明显的差别,即由松辽盆地地壳的三分性变到东缘域盆地外地壳的二分性,在剖面近东端得到近26 km深的莫霍界面深度,并用均衡理论分析莫霍界面形态特征的形成机理;上部地壳存在双向大型推覆断裂,推测其被推覆体主体是古亚洲洋沉积地层即C-P系海相地层.这些认识为中国东北地区探查晚古生代海相地层、研究东北亚地壳结构特征提供了理论依据.

     

松辽盆地东缘域地壳结构及其地质意义:深反射地震

松辽盆地东缘域位于松嫩—张广才岭微板块东部.自晚古生代以来该域经历了西拉木伦河缝合带闭合产生的北向挤压作用、蒙古—鄂霍茨克洋自西向东剪刀叉式闭合对其东侧东南侧产生的挤压作用以及西太平洋板块西向变向俯冲产生的挤压作用等区域构造应力场影响,从而产生了复杂的地壳变动.该东缘域的地壳结构与松辽盆地地壳是否具有相近的结构特点,这是至今未被研究的内容.在Songliao Drep研究中已经用深反射地震手段得到松辽盆地地壳结构的一组新认识.这些认识在其东缘域是否还成立,也需要用同样精度的手段予以研究.另外,莫霍界面的宏观特征与微观（内部）特征,从松辽盆地到其东缘域有什么样的变化,其形成机理是什么,也需要进一步研究.为了回答这些科学问题,从哈尔滨西至尚志市附近实施了一条东西向约150 km长的深反射地震剖面.通过研究发现东缘域与松辽盆地基底地壳具有明显的差别,即由松辽盆地地壳的三分性变到东缘域盆地外地壳的二分性,在剖面近东端得到近26 km深的莫霍界面深度,并用均衡理论分析莫霍界面形态特征的形成机理;上部地壳存在双向大型推覆断裂,推测其被推覆体主体是古亚洲洋沉积地层即C-P系海相地层.这些认识为中国东北地区探查晚古生代海相地层、研究东北亚地壳结构特征提供了理论依据.     

松辽盆地西边界带深部构造:地电学证据

满洲里—绥芬河地学断面综合研究了松辽盆地西、东边界的构造特征.在由广角地震波速分布所得到的认识基础上,本文利用松辽盆地西边界带附近新实施的大地电磁测深(MT)(约470 km 42个测点)剖面,经过数据处理的二维电性分布,更为详细地表达了西边界带深部构造特征.与满—绥断面研究相近的结果是西边界带的断裂构造表现为作为盆地西边界的嫩江断裂,在地表附近与黑河—贺根山缝合带断裂叠加在一起,于深几公里以下两条断裂分开,缝合带断裂西倾并穿过地壳,嫩江断裂东倾而且可能不超壳.本次研究与满—绥断面研究不同点是两条断裂分开部位之下的构造表现.由于兴安微板块与松嫩微板块间碰撞、焊合以及边界断裂走滑等复杂区域应力场作用,留存的岩石圈残片被分割在嫩江断裂两侧.所建立的地质-地球物理解释模型提供了西边界带可能的构造地质作用过程.     

Migration of growth axial surfaces and its implications for multiphase tectono-sedimentary evolution of the Zhangwu fault depression,southern Songliao Basin,NE China

The normal fault-bend folding theory uses active axial surfaces, inactive axial surfaces, and growth axial surfaces to describe the geometric relationship between faults and deformation of a hanging wall. The dip of a growth axial surface is related to the fault slip rate and the basin sedimentation rate: higher fault slip rates result in smaller dips of growth axial surfaces, whereas higher basin sedimentation rates produce larger dips of growth axial surfaces. Moreover, the growth axial surface will be a straight line if both the fault slip and sedimentation rates remain relatively unchanged, but will become curved if both rates are variable. Therefore, the characteristics of growth axial surfaces can provide clear information on the evolution of faulting and deposition. By studying the seismic profiles of the Zhangwu fault depression of the southern Songliao Basin, we show that the migration of growth axial surfaces and unconformities can be used as indicators of basin development. Multiphase tectonic activity will not only produce unconformities but also result in migration of growth axial surfaces or inactive axial surfaces. Therefore, the normal fault-bend folding theory, particularly with regard to the evolution of growth axial surfaces, can be applied to the interpretation of geometric and kinematic evolutions of half-grabens and the exploration of related tectono-sedimentary processes.     

Late stage thermal history of the Songliao Basin and its tectonic implications: Evidence from apatite fission track (AFT) analyses

Apatite Fission Track (AFT) data from the Songliao Basin indicates that the late stage tectonic movements in the Songliao Basin have zoning in space and episodes in time. The late stage tectonic movements started from the east part of the basin and migrated westward. AFT ages in the east part of the basin are older than those in the west part of the basin, suggesting that the uplift occurred earlier in the east than in the west. The denudation thickness in the east part of the basin is significantly greater than that in the centre and west. The thermal history evolved two episodes of rapid cooling and subsequent slow cooling processes. Age-depth relationship derived from the AFT data indicates a four-episode denudation history. Further Monte Carlo random simulation of the AFT data reveals the four changing points of the thermal evolution at 65 Ma, 43.5 Ma, 28 Ma and 15 Ma, respectively. The uplifting and denudation rates from different episodes of evolution are proportional to the plate convergence rate. Based on the above analyses and the regional geologic background, it is concluded that the late stage thermal events in the Songliao Basin are the far field response to the subduction of the Pacific Plate under the Eurasian Plate. The first episode of the rapid cooling probably started at the end of the Nenjiang Formation, climaxed at the end of the Cretaceous and ceased at the Late Eocene. The subsequent slow cooling lasts another 15 Ma. The first episode of the evolution is the far field response to the major episode of the Yanshan Movement and subsequent series of the tectonic reorganization, especially the directional change of the Pacific Movement and also the subduction of the Indian Plate underneath the Eurasian Plate. While the second episode of the evolution is the far field response to the extension and closure of the Sea of Japan. Extension led to the migration and converging of the mantle heat flow to the Sea of Japan and resulted in the rapid cooling of the Songliao Basin.