燕山运动“绪动/A幕”的本意及其锆石 U-Pb年代学制约

"燕山运动"提出已有90余年。该概念从产生之日到现在一直存在着巨大争论。本文首先回顾了该概念的原始含义及其存在的逻辑问题。翁文灏将燕山运动分为三个阶段:"绪动"阶段、即A幕;火山幕、或称为中间幕;B幕。"绪动/A幕"的本意指上火山岩系下部砾岩与煤系地层之间的不整合事件。需强调翁文灏所谓的上火山岩系包括了主体的火山岩和火山岩之下的砾岩。这套砾岩在辽西为海房沟组、在北京西山为龙门—九龙山组。翁文灏认为砾岩产生于燕山运动的"绪动/A幕",但"绪动/A幕"与"火山幕"的关系翁文灏认为难以阐述清楚。翁文灏在提出燕山运动(Yenshan movement)之后、丁文江提出了燕山期运动(Yenshanian movement)的名词。后续的研究者多因循"燕山期运动"的思想,但在中文表述中几乎只使用"燕山运动"的文字表述,这造成了逻辑上理解的差异,二者显然是不同的概念范畴,需予以区分。理清原始概念之后,本文通过位于北京西山雁翅镇田村、淤白村附近的钻孔和探槽,揭露出北京西山九龙山组底部的一套厚约12m火山凝灰岩。凝灰岩之下发育一套砾径可达2m、碳酸岩质的砾岩,与其下寒武纪地层呈不整合接触,代表"绪动/A幕"的不整合面。凝灰岩的锆石LA-ICP-MS U-Pb年代学测试揭示了154Ma和161Ma两期年龄,前者限定了九龙山组的底界年龄,后者可能代表了"绪动/A幕"发生的最早火山响应。最后本文依据不整合面穿时性特点指出位于龙门—九龙山组砾岩之下的不整合面在空间上应收敛于髫髻山组火山岩之下的不整合面。而龙门—九龙山组砾岩与髫髻山组火山岩具有同时异相的空间特征。     

燕山中段常州沟组底砾岩的成因类型

根据底砾岩的砾石成分、结构、分布、产状及沉积相序等特征,将燕山中段常州沟组底砾岩分为冲积扇沉积、河流沉积、扇三角洲沉积、海滩沉积等４种成因类型,并探讨了常州沟早期燕山盆地的岩相古地理格局。     

燕山中段常州沟组底砾岩的成因类型

根据底砾岩的砾石成分,结构,分布,产状及沉积相序等特征,将燕山中段常州沟组底砾岩分为冲积扇沉积,河流沉积,扇三角洲沉积,海滩沉积等４种居因类型,并探讨了常州沟早期燕山盆地的岩相古地理格局。     

川西前陆盆地南部中新生代砾岩的构造意义

通过对龙门山前缘川西前陆盆地南部中新生代地层中砾岩的岩石学特征、年代及分布规律的对比研究，认为五龙沟砾岩、大溪砾岩及大邑砾岩是龙门山造山运动的沉积响应；龙门山的崛起是一个多阶段性的持续过程，其发生的时限依次对应于燕山早期、燕山晚期-喜马拉雅初期、喜马拉雅晚期。     

准南前陆盆地燕山期构造活动及其成藏意义

准南前陆盆地燕山期盆地格局的演变、沉积中心有规律的迁移、沉积特征(与构造活动相关的砾岩及其分布)显示晚侏罗世—早白垩世早期、晚白垩世是准南前陆盆地燕山期构造活动相对活跃的时期。晚侏罗世—早白垩世早期的喀拉扎砾岩、白垩系清水河组底砾岩为一套形成于邻近高地附近的剥蚀产物或冲积产物,其分布特征及成因是晚侏罗世—早白垩世早期局部挤压和构造隆升较为活跃的产物,也是盆地边界萎缩、盆山格局发生变化的重要证据,同时天山明显隆升并导致天山南北早白垩世沉积环境的巨大差异。准南前陆盆地烃源岩大量生排烃、圈闭形成、油气运聚成藏与燕山期构造活动关系密切;燕山期发育的储层是准南前陆盆地的主要油气储层,晚侏罗世—早白垩世早期砂砾岩和不整合分布也在一定程度上控制了油气分布,是今后寻找有利隐蔽油气藏、岩性地层油气藏的重要目标之一;燕山期古构造及其形成时间与油气成藏期的良好匹配决定其油气成藏的有效性。     

河南祁雨沟金成矿系统辉钼矿Re-Os年龄和锆石U-Pb年龄及Hf同位素地球化学

河南祁雨沟金矿位于秦岭造山带最北部,属典型的角砾岩筒型成矿系统。矿区16号角砾岩筒下伏斑岩体锆石的ε_Hf(t)值为-10.50~-14.43,Hf模式年龄为2.57~2.93Ga,表明花岗斑岩主要来源于古老下地壳的部分熔融。锆石LA-ICPMS U-Pb年龄为134.1±2.3Ma,与7号角砾岩筒中的辉钼矿Re-Os等时线年龄135.6±5.6Ma一致。这些年龄数据与熊耳山地区燕山期花岗岩体的侵位年龄基本相同,共同指示其形成于地壳缩短增厚之后的伸展减薄过程。熊耳地体的地壳缩短增厚缘于同碰撞时期沿马超营断裂带的A型俯冲作用,而A型俯冲导致了包括祁雨沟金矿系统、燕山期花岗岩类和脉状造山型矿床在内的熊耳矿集区的形成。     

准噶尔盆地西北腹部燕山期构造活动与沉积响应

燕山运动是侏罗纪/白垩纪之交,区域规模和岩石圈尺度的重大构造运动.与中国东部地区相比,该运动在中国西部盆地的岩浆作用、构造事件动力学机制及其沉积响应等方面还存在诸多争议.利用碎屑锆石年代学和砂岩岩相学分析,对准噶尔盆地腹部石南地区的燕山期构造运动及盆地内的沉积响应进行分析,得到以下认识:（1）准噶尔盆地腹部侏罗纪-白垩纪同沉积期火山活动相关碎屑锆石是燕山期区域性火山活动的重要沉积响应.（2）准噶尔盆地燕山期发生强烈的陆内造山运动,盆地内构造单元发生相应的挤压变形.（3）准噶尔盆地内沉积体系对燕山期构造运动具有良好响应,白垩系底砾岩指示了盆地周缘造山带的快速隆升和盆地边界的萎缩.      

易门、峨山的花岗岩是古生代的侵入体

易门、峨山一带出露的几个花岗岩株,一直被人们看做是燕山期的产物。最近,我们在易门赵普发现这里岩株上复的禄丰层底部,有以花岗岩物质为砾石材料的底砾岩。禄丰层以北70°东-北75°西走向,向南10°-25°倾斜,并且极为稳定而平整地     

大别造山带燕山期造山作用的岩浆岩石学证据

在区域地质填因基础上研究了大别地区燕山期岩浆岩，重新划分了该区燕山期岩浆作用期次，发现大别地区在燕山期存在一个完整的造山岩浆旋回。首次提出本区燕山晚期岩浆岩为双峰式组合，与燕山早期岩浆岩属高钾钙(碱)性—钾玄岩组合一起构成一个从挤压到伸展的造山岩浆旋回，成为燕山期造山的重要佐证。岩浆岩成因特点揭示出本区的岩石圈结构在燕山期存在一个从双倍陆壳到正常陆壳的过程，深部地质过程则是底侵作用和拆沉作用的继续。     

“燕山运动”的分期及几个关键问题

翁文灏最初定义的"燕山运动"主要根据《北京西山地质志》所提供的信息,当时并未对"燕山运动"分期。在赴辽西北票地区考察后,翁文灏将"燕山运动"分为A、B两期,A期为绪动,B期为主要期。详细的文献研读发现,翁文灏对"燕山运动"在北京西山和辽西的原始定义有出入。经对比分析,本文认为在北京西山一带代表"燕山运动"的主不整合面应在上窑坡组煤系地层与龙门组砾岩之间,在辽西一带应为北票组煤系地层与海房沟组砾岩之间。另外,本文认为"燕山运动"的A期(绪动)可能与中国东部北东向区域性大断裂发生同时。最为重要的是,本文认为A期"燕山运动"形成于极短的时间,如同时间坐标上的一个点,这个点构成了B期的边界点。     

Characteristics of geothermal reservoirs and utilization of geothermal resources in the southeastern coastal areas of China

Based on regional geological setting, stratigraphic distribution and other geological conditions, this paper summarized three types of geothermal reservoirs in the southeast coastal areas of China: Cenozoic sandstone or sandy conglomerate reservoir, Mesozoic granite fissure reservoir and Paleozoic karst reservoir. Cenozoic sandstone or sandy conglomerate reservoirs are mainly located in Cenozoic basins, such as Zhangzhou, Fuzhou, Sanshui and Leiqiong basins. The Tertiary sedimentary basins such as Leiqiong Basin and Sanshui Basin, are controlled by NE-trending faults, while the Quaternary sedimentary such as Zhangzhou and Fuzhou basins are controlled by NW-trending faults. Mesozoic granite fissure reservoirs are mainly distributed in the southeast coastal areas, such as Zhangzhou, Fuzhou, Fengshun, Yangjiang and southern part of Hainan Province. The distribution of good Mesozoic granite fissure reservoir in these areas is mainly controlled by NE-trending faults. Paleozoic carbonate reservoirs are widely distributed in these areas. Most carbonate rocks are from the upper Paleozoic strata, such as those in the area of Huizhou in Guangdong Province. The major types of geothermal systems in the southeast coastal areas of China belong to medium and low-temperature convection. The geothermal resources developed from the ground to-3 000 m underground could be utilized directly for space heating, greenhouse heating, aquaculture pond heating and industrial uses, as well as other purposes. The geothermal resources with a depth of 3 000～6 000 m underground is mainly featured by Hot Dry Rock(HDR) with a temperature ranges from 150 ℃ to 200 ℃, which is conductive to the development of Enhanced Geothermal System(EGS) and can be utilized for power generation.     

Insight into the Cenozoic tectonic evolution of the Qaidam Basin, Northwest China from fracture information

Fractures can provide valuable information for tectonic evolution. According to the data of outcrops, cores, thin sections and well logs, the tectonic fractures in the Qaidam Basin can be divided into four types: small faults (including small normal fault and small reverse fault), vertical open fracture, bedding plane slip fracture and horizontal open fracture. Our fracture observations provide new constraints on the Cenozoic tectonic evolution of the Qaidam Basin. Syn-sedimentary small normal faults in the Paleogene strata indicate the extension deformation during the Paleogene. Small reverse faults, vertical open fractures and bedding plane slip fractures occurred in the Paleogene and Neogene strata have genetic relationship. According to the burial history and homogenization temperature of fluid inclusions of gypsum and calcite filled in the vertical open fractures, it can be deduced that the vertical open fractures being formed mainly from the late Miocene Shangyoushashan Formation with age of 5.1?Ma to the end of Pliocene Shizigou Formation with age of 2.6?Ma, indicating small reverse faults, vertical open fractures and bedding plane slip fractures were simultaneously formed in the Neogene. These fractures were resulted from the compression deformation. The horizontal open fractures occurred in the Paleogene, Neogene and Quaternary strata with apertures and intensities decreasing with depth were formed by the large-scale quick uplift and denudation resulted from the strong compression deformation since the Quaternary.     

湖南锡田锡钨多金属矿床成矿构造特征及其找矿意义

锡田矿床内发育近SN向花岗岩穹窿伸展构造、NE向复式褶皱和NE或NEE向走滑伸展构造系统。穹窿构造主要由印支期和燕山期侵入的花岗岩和古生代地层及不连续的环形滑脱断层组成,控制燕山期花岗岩与围岩接触带矽卡岩型矿体的分布;复式褶皱为古生代地层组成的NE向复式向斜,在矿区中部被锡田复式花岗岩体切割。严塘复式向斜与小田复式向斜中的背斜核部,尤其断层叠加的部位常控制一些构造破碎带型钨锡富矿体的分布。NE向或NEE向走滑伸展构造系统包括NE向右行(伸展)走滑断层、NE向或近EW向右行次级的走滑伸展断层、近SN向左行走滑断层和NW向伸展断层,控制了锡田矿区内的不同方向构造蚀变岩型、石英脉型和云英岩脉型锡钨多金属矿床的分布。花岗岩锆石U-Pb、白云母40Ar-39Ar和辉钼矿Re-Os同位素测年表明锡田地区燕山期构造活动、岩浆作用与成矿响应时间非常接近,介于150～160Ma。岩体与地层(灰岩)接触带、岩体中的NEE向断裂带以及被NE向断裂叠加的背斜轴部是重要的成矿区域,可作为下一步矿产勘查工作重要靶区。     

Cenozoic Magmatism and Tectonic Framework of Western Yunnan, China: Constrained from Geochemistry, Sr–Nd–Pb Isotopes and Fission Track Dating

Western Yunnan is composed of several extruded continental microblocks that were generated by the oblique collision between the Indian and Asian continents during the Cenozoic. In this study, the magmatic and tectonic frameworks of western Yunnan in the Cenozoic were analyzed based on geochemistry, Sr–Nd–Pb isotopes, and apatite/zircon fission track dating. Magmatism during the Cenozoic in western Yunnan was then divided into three distinctive episodes: alkali granite rocks produced from 55 to 46 Ma were derived from the anatexis of crustal materials; bimodal igneous rocks formed between 37 and 24 Ma were possibly derived from an EMII mantle with a contribution from continental materials; and intermediate–basic volcanic rocks produced in the Tengchong microblocks since ~16 Ma are considered to be generated by the partial melting of the upper mantle that was induced by the pulling apart of the dextral Gaoligong strike–slip fault system. Moreover, fission track analysis of apatite and zircon indicates that the regional crustal uplift in western Yunnan possibly began at ~34 Ma, with accelerated annealing occurring at ~24 Ma, ~13 Ma, and ~4 Ma. During the past 24 Ma, the average denudation rate was ~0.32 mm/yr for the faulted block controlled by the Chongshan–Lancang River fault. However, crustal uplift has been relatively gentle in places lacking influence from strike–slip shear zones, with an average denudation rate of ~0.2 mm/yr. Combined with strike–slip shear and block rotation in the Cenozoic, the tectonic evolution of western Yunnan since ~45 Ma can thus be divided into four stages occurring at 45–37 Ma, 37–24 Ma, 24–13 Ma, and 13–0 Ma.     

阿尔金断裂带新生代活动在柴达木盆地中的响应

阿尔金断裂新生代以来发生多期次的走滑运动,并伴随强烈的隆升作用,进而影响柴达木盆地新生代的构造演化。本文通过遥感卫星影像解译、地震反射剖面解释、区域地层分析,结合野外考察资料对阿尔金断裂新生代活动在柴达木盆地中的响应进行了研究。对柴达木盆地卫星影像的解译发现盆地中褶皱形态指示了近东西走向的褶皱构造带与近南北走向的褶皱构造带的叠加干涉效应,其中近东西向褶皱构造带是在印度/欧亚板块碰撞作用下青藏高原隆升并向北东扩展过程的响应,近南北向褶皱构造带是阿尔金断裂新生代活动的响应。对NW-SE向穿过阿尔金山-柴达木盆地的盆山结合带地震反射剖面的再解释,发现新生代地层中发育的多层生长地层,记录了阿尔金断裂新生代活动的信息。对盆地中新生代地层分布等厚图褶皱干涉样式的分析表明,上油砂山组沉积时期(14.9Ma)阿尔金断裂活动已经明显影响到柴达木盆地,而狮子沟组沉积时期(8.2~2.6Ma)断裂活动对柴达木盆地改造最强。通过对研究区已有的低温热年代学数据和沉积、构造、磁性地层年代学等方面研究成果的总结和分析,认为阿尔金断裂在新生代至少存在三期(~30Ma,~8Ma、~2.6Ma)强烈的构造活动和隆升作用,在柴达木盆地内表现为相应地质时代沉积速率的加快、沉积物岩性的变化、构造地貌的变形和同构造生长地层的出现。其中后两期(~8Ma、~2.6Ma)构造活动在整个青藏高原及周边地区广泛存在,为准同期构造事件,而月牙山地区地震地表破裂带的发现则表明阿尔金断裂带现在仍在强烈活动,并且直接影响到了柴达木盆地。阿尔金断裂带新生代以来的构造活动具有多期性,并影响和改造了柴达木盆地,可能对油气成藏有重要影响。     

Late Cretaceous‐Cenozoic Multi‐Stage Denudation at the Western Ordos Block: Constraints by the Apatite Fission Track Dating on the Langshan

The apatite fission track dating of samples from the Dabashan(i.e., the Langshan in the northeastern Alxa Block) by the laser ablation method and their thermal history modeling of AFT ages are conducted in this study. The obtained results and lines of geological evidence in the study region indicate that the Langshan has experienced complicated tectonic-thermal events during the the Late Cretaceous-Cenozoic. Firstly, it experienced a tectonic-thermal event in the Late Cretaceous(~90–70 Ma). The event had little relation with the oblique subduction of the Izanagi Plate along the eastern Eurasian Plate, but was related to the Neo-Tethys subduction and compression between the Lhasa Block and Qiangtang Block. Secondly, it underwent the dextral slip faulting in the Eocene(~50–45 Ma). The strike slip fault may develop in the same tectonic setting as sinistral slip faults in southern Mongolia and thrusts in West Qinling to the southwest Ordos Block in the same period, which is the remote far-field response to the India-Eurasia collision. Thirdly, the tectonic thermal event existed in the late Cenozoic(since ~10 Ma), thermal modeling shows that several samples began their denudation from upper region of partial annealing zone(PAZ), and the denudation may have a great relationship with the growth of Qinghai-Tibetan Plateau to the northeast. In addition, the AFT ages of Langshan indicate that the main body of the Langshan may be an upper part of fossil PAZ of the Late Cretaceous(~70 Ma). The fossil PAZ were destroyed and deformed by tectonic events repeatedly in the Cenozoic along with the denudation.     

鲁西地块NW走向断层的活动特征及裂变径迹证据

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。     

郯庐断裂带莱州湾段新生代活动演变及其沉积-改造效应

本文根据对覆盖区地震、钻井等资料的精细解释和深入剖析,揭示在渤海莱州湾地区郯庐断裂带由东、西两条分支断裂带构成,二者又分别由两条主断层及多条次生断层和其间的断块组成。分支断裂带的两条主断层的间距因地而异,一般在5km左右;其结构构造和空间展布特征有别,西支表现为"两断夹一凸"的不对称地垒式,东支主要呈"花状"构造结构。通过古地质构造恢复和分期动态构造演化分析等综合研究,厘定了在新生代不同时期两条分支断裂带在该区不同单元的活动特点和构造-改造效应,进而总结了郯庐断裂带新生代主要阶段的构造属性及其演变。认为在古近纪早中期,研究区处于区域伸展沉降环境,郯庐断裂带对该区的沉积展布无明显控制作用;断裂带活动的明显控制沉积效应始于古近纪晚期,总体具伸展兼右行走滑属性,主要表现为切割和改造了研究区原近东西向展布的优势构造-沉积格局,同时控制了前期沉积地层的剥蚀强度及其分布范围和同期沉积。新近纪以来,郯庐断裂带两条分支断裂带的活动表现出差异显著的东强西弱;于第四纪,在东支断裂带出现正花状反转构造,可能与幕式走滑兼挤压活动有关。     

Application of the non-seismic geophysical method in the deep geological structure study of Benxi-Huanren area

Based upon 1:200,000 regional gravity and aeromagnetic data, gravity and aeromagnetic slice maps were obtained through fast Fourier transformation (FFT) upward continuation. A comparison between gravity and aeromagnetic slice maps at different depths combined with regional geological data and Magneto-Telluric sounding reveals the deep geological structure of Benxi-Huanren area and provides important information for study of the deep geological evolution process of Benxi-Huanren area. Yanshanian granitic pluton is widely distributed in this area and tends to be continuous toward depth. Significant metallogenic areas, such as Dataigou and Nanfen areas, lie above the buried granitic pluton. The Paleoproterozoic strata distribution area and the Archean strata distribution area have similar characteristics in terms of gravity anomaly. The iron-bearing formation in Anshan area is Archean supracrustal rock which was not engulfed by Archean granite. The thickness of Liaoji paleo-rift can be up to 10 km, whose lower part was intruded by Yanshanian granites. The basement of the Liaoji rift was remelted during granite intrusion in Yanshanian period.     

赣南兴国杨村岩体锆石U-Pb年龄测定及其地质意义

位于南岭东段北部赣南地区兴国县境内的杨村岩体,侵入于前寒武纪基底变质岩中,其西侧又与白垩系赣州组砂岩、砾岩断层接触,因而其地质年代难以根据接触关系准确判断,而岩体本身风化程度比较高,难以利用K-Ar法和Rb-Sr等时线等方法获得可靠年龄,以往将该岩体归属于加里东期。文章采用激光剥蚀-多接收器电感耦合等离子体质谱(LA-MC-ICPMS)锆石U-Pb定年方法,获得其锆石206Pb/238U加权平均年龄为(175.8±1.0)Ma,从而准确地查明该岩体侵位于燕山早期第一阶段与第二阶段的过渡时期。这一阶段在南岭是钨多金属发生大规模成矿作用的开始阶段,因而杨村岩体地质年代的确定为今后的地质找矿提供了新的线索。