北京“洼里砾岩”的成因及时代探讨

关于北京“洼里砾岩”成因的争议由来已久,主要有构造成因和沉积成因两种不同的观点。在以往资料的基础上,结合近年来新的地热钻井资料,绘制了地质剖面图,进行了地层比对与构造分析,发现剖面中存在数条、多期、规模不一的逆断层,存在相互切割,这使得地层受到较大扰动,体现出八宝山断裂的逆冲作用非常强烈,且具有多期性;并在构造分析的基础上,结合砾岩的成分、结构、岩溶发育及出现层位等岩性特征,以及北京凹陷的形成过程,分析了其形成机制,提出“洼里砾岩”属于八宝山断裂带断层角砾岩雾迷山组内的部分,形成时代大约是在中生代中晚期。      

北京“洼里砾岩”地质特征及时代讨论

洼里砾岩的隐伏性和岩性特征决定了确定其成因及地层归属的困难。由于洼里砾岩紧邻八宝山断裂和黄庄－高丽营断裂，并且赋存丰富的地下水，所以研究洼里砾岩的成因和地层时代归属具有重要的基础地质和工程地质意义。随着近年地热深钻孔对洼里砾岩的揭穿，揭示其与下伏侏罗系九龙山组呈角度不整合接触，岩性特征表明它是由流水沉积作用形成的，属正砾岩岩块砾岩类，地层时代应归属侏罗系上统髫髻山组的下部。     

北京北苑地区洼里砾岩地层地热井钻井技术

洼里砾岩地层是北京洼里地区一种特殊的砾岩地层。分析了其地质特征、成因及对钻探施工的影响，介绍了在此地区施工的3眼地热井所采用的钻井设备及工艺、钻进中存在的困难及采取的措施。     

滇中昆阳群因民角砾岩及其成因

“因民角砾岩”的成因问题是一个争论已久的问题，至今仍未有统一的认识。笔者通过对滇中和东川地区“因民角砾岩”的观察，对其进行了详细的分类。根据其成因划分为沉积砾岩（包括复成分砾岩、滑塌角砾岩与石英砾岩）、火山角砾岩与构造角砾岩（包括断层角砾岩与水力张裂角砾岩）。对“因民角砾岩”成因的研究，特别是“水力张裂角砾岩”的提出，对于解决昆阳群的地层层序，了解滇中元古宙地壳演化以及进一步找矿都具有重要的意义。     

基于多源数据分析的洼里砾岩地下水循环特征

利用钻孔、地下水位、水质、温度和同位素等多源数据,识别了洼里地区的地质结构、地下水动态、地下水化学、地下水温度和同位素特征,分析了洼里砾岩与奥陶系、第四系含水层的水力联系。洼里砾岩在西部与奥陶系地层直接接触,与奥陶系含水层存在水量交换通道;洼里砾岩与奥陶系和第四系地下水水位具有一致的年际和年内变化特征,水位高值一般出现在1—2月,水位低值出现在5—6月。同时,洼里砾岩、第四系和奥陶系地下水水化学类型均为HCO3-Ca·Mg型,且C-14和S-34同位素值相近,地下水温度变化规律具有区域一致性。结果表明,洼里砾岩岩溶发育,富水性好,与奥陶系和第四系含水层水力联系密切。地下水循环特征表现为:地下水主要接受西部奥陶系地下水补给,自西南向东北方向径流,主要排泄方式为侧向径流和向第四系含水层越流。     

广西下,中三叠统砾质岩类特征及成因探讨

文章分析论述了广西下，中三叠统砾质岩类所在层位及其特征，并将其划分为水道砾岩，崩塌－滑塌砾岩，沉积混杂岩３种成因类型，探讨了形成环境及其意义，指出它们均是三叠纪时期构造作用的沉积表现。     

松辽盆地东南缘六台地区下白垩统营城组二段砾岩沉积特征及成因模型

松辽盆地东南缘六台地区营城组二段发育一套冲积扇砾岩层。根据砾岩成因不同分为泥石流砾岩、河道砾岩和漫流砾岩等沉积类型,其中泥石流砾岩最为发育。通过研究泥石流砾岩的成分、结构成熟度和粒度分布特征,并运用经验公式最终判断其为再沉积的水上泥石流砾岩。河道砾岩和漫流砾岩沉积类型在本区保存较少,或许曾经在单个旋回中非常发育,但是被下个旋回猛烈的泥石流所改造。河道砾岩和漫流砾岩中层理的收敛方向及硅化木走向均表明本区古水流方向为近北西—东南向。根据古水流向等信息判断出本区砾岩的物源来自北西方向的北山,并在此基础上建立了本区砾岩冲积扇成因模型。     

冀东朱杖子群老爷庙变质砾岩的成因

朱杖子群老爷庙变质砾岩长期以来一直被认为是沉积成因的,并将其作为冀东地区元古界与太古界地层的分界标志(张树业等,1960)。近年来随着工作的深入,对该变质砾岩的成因提出了质疑,认为它可能属于火山成因(董申保,1978),因而它不能作为元古界与太古界地层划分的界限。但有人,如白瑾(1978)和谭应佳等(1979)仍维护该变质砾岩沉积成因的观点,并重新论证了其沉积底砾岩性质和以它为界的该区元古界与太古界地层之间的角度不整合关系。     

西秦岭徽县-成县早白垩世盆地沉积特征及其构造意义

徽县-成县(徽成)盆地是西秦岭造山带内一个具有代表性的早白垩世走滑拉分盆地。沉积相分析结果显示,盆地内部发育不同的沉积相组合,且呈现明显的时空变化特征。盆地充填序列分析表明,徽成盆地的沉积演化可划分为4个阶段:田家坝组沉积时期、周家湾组沉积时期、鸡山组沉积早期和鸡山组沉积晚期。田家坝组沉积时期,盆地南部以冲积扇砾岩和辫状河砂、砾岩沉积组合为主;周家湾组沉积时期,盆地西部以冲积扇砾岩和辫状河砂、砾岩沉积组合为主;鸡山组沉积时期,盆地北部和南部以冲积扇砾岩和辫状河砂、砾岩沉积为主。在整个沉积过程中,盆地中心表现为湖泊(前三角洲)相细粒沉积,而河流和三角洲体系则分布于冲积扇和深水湖泊(前三角洲)沉积之间。古流向和物源恢复结果证明,盆地沉积物主体来自于盆地北部、南部的花岗岩和前侏罗纪地层。盆地构造沉降和沉积充填过程主要受控于盆地北缘徽凤断裂,盆地南部抬升与盆地边界断层的活动密切相关,是盆地的主要物源区。     

黑龙江东部林口地区下白垩统穆棱组砾岩的成因及其意义

大三江地区是中国东部重要的油气资源接替区,早白垩世时期该地区曾为一个统一的盆地,之后盆地遭受破坏分解。如何确定当时的盆地边界进而恢复盆地原型,是该地区亟待解决的关键地质问题之一。前人对盆地边界的确定大都以理论推测为主,缺乏实际证据。本次工作在黑龙江林口地区发现一套穆棱组底部砾岩,对砾石进行成分及分选特征、沉积特征等的统计与分析,结合古水流恢复和地震解释资料,认为该套砾岩整体为冲积扇相,以河道砾岩沉积和漫流砾岩沉积为主,物源主要来自盆地西部的张广才岭。结合地震资料分析,认为研究区穆棱组时期的沉积模型为冲积扇相向滨浅湖亚相的直接过渡。本研究不仅为大三江盆地西部边界的确定提供了直接证据,同时也为该地区今后的油气勘探指明了方向。     

Coniacian carbonate-conglomerate event on carbonate ramps from the Northern Chotts ranges,South Tunisia: facies geometry and tectono-sedimentary evolution

Conglomerate bodies are wide spread in the Lower Coniacian carbonate of the southern of Tunisia. This paper presents an examination of the stratigraphic architecture of these Coniacian conglomerates. It aims to the understanding of the processes leading to their genesis and the relationship and context with the late Cretaceous sedimentation. These conglomerates are related to the incision of Aptian palaeovalleys in a carbonate platform in an extensional setting. The sedimentary analysis and the geometry of these bodies show that the Cretaceous succession in this area are formed by eight facies within four facies associations, representing a series of distinct depositional environments ranging from alluvial plain to the open marine environment. The sedimentary analysis allowed the recognization of elementary sequence which start with the conglomerate bodies corresponding to the incised valley fills.     

禄丰腰站以东前震旦系地层及沉积环境

依据腰站以东前震旦系各组岩性特征、沉积构造、叠层石发育情况,划分为滨海环境、潮间带环境、浅海环境、半深海-深海环境;将孝母山砾岩确定为层间砾岩性质。     

Provenance of the Pythian Cave conglomerate,northern California: implications for mid-Cretaceous paleogeography of the U.S. Cordillera

Provenance analysis of middle Cretaceous sedimentary rocks can help distinguish between disparate tectonic models of Cretaceous Cordilleran paleogeography by establishing links between sediment and source, as well as between currently separated basins. This study combines new detrital zircon age data and compositional data with existing provenance data for the Pythian Cave conglomerate, an informally-named unit deposited unconformably on the eastern Klamath Mountains, to test possible correlations between the Pythian Cave conglomerate and similar-age deposits in the Hornbrook Formation and the Great Valley Group. These provenance results indicate that restoring Late Cretaceous clockwise rotation of the Blue Mountains adds a significant sediment source for Cretaceous basins previously associated with only the Klamath Mountains (e.g., the Pythian Cave conglomerate and Hornbrook Formation) or a combined Klamath-Sierran source (e.g., Great Valley Group). Comparison of the Pythian Cave conglomerate with the Klamath River Conglomerate and the Lodoga petrofacies suggests that the Pythian Cave conglomerate system was separate from the nearby Hornbrook Formation and was probably related to the Lodoga petrofacies of the Great Valley Group.     

祁连山老君山砾岩的碎屑组成和源区大地构造背景

老君山砾岩是一套由砾岩和杂砂岩组成的陆相粗碎屑岩.砾岩由来自下伏基底的超镁铁岩、中-基性火山岩、硅质岩、花岗岩等碎屑组成.杂砂岩中岩屑含量大于70%,石英约10%,长石约15%.岩屑以中基性火山岩和花岗岩为主;硅质岩屑是主要的沉积岩屑.锆石、磷灰石、磁铁矿是杂砂岩中最为丰富的重矿物,同时还有铬铁矿、石榴子石、电气石、金红石、黄铁矿.这些事实说明,老君山砾岩的源区曾出露有超镁铁岩、中基性火山岩、变质岩等类型的岩石.砂岩碎屑模式和粉砂岩、泥岩的地球化学成分均表明,老君山砾岩源区为大陆边缘弧和大洋岛弧,形成于活动大陆边缘与岛弧相关的沉积盆地中.     

The sedimentary record of the exhumation of a granitic intrusion into a collisional setting: the lower Gonfolite Group,Southern Alps,Italy

The clastic wedge of the Gonfolite Lombarda Group (GLW) accumulated during Oligocene–Miocene times in the Southern Alps foreland basin, formed on the southern, inner side of the Alpine belt. It represents the depositional counterpart of the exhumation and erosion of the Central Alps metamorphic–magmatic units.Among the Central Alps units, the Tertiary Bergell Intrusion (TBI) is one of the principal sources of pebbles occurring within the GLW. Geochronologic data, both from intrusive pebbles and present-day outcrops of intrusive rocks, document the rapid uplift history of the GLW source area.The lower Gonfolite clastic wedge (Como Conglomerate and Val Grande Sandstone Formations, Oligocene–Early Miocene) has been investigated through the study of sandstone and conglomerate petrology for detecting the effects in the sedimentary record of this collision-related event.The main results are: (i) sandstone petrology of the Como Conglomerate records an evolution from feldspatholithic to feldspathic sandstones; (ii) the related Q/F–F/L ratios suggest an evolution from a mixed plutonic–metamorphic to a mainly plutonic source; (iii) consistently, conglomerate petrology records a progressive increase of plutonic pebbles (from nearly 0–50% of the total), a corresponding decrease of metamorphic clasts (from nearly 80 to nearly 50%) and the disappearance of cover rock fragments. Considering the high relief/short transport setting of the GLW clastic routing system, these values probably resemble the real proportions of such rocks in the Gonfolite catchment area.During the Aquitanian, the return to a metamorphic-rich source is recorded both by sandstones and conglomerates at the top of the Como Conglomerate and in the Val Grande Sandstone. This last signal is interpreted as the result of the reorganisation of the Gonfolite source area, possibly related to the northward shift of the main Alpine divide.     

Clastic sedimentation in the Late Oligocene Southalpine Foredeep: from tectonically controlled melting to tectonically driven erosion

The Villa Olmo Conglomerate (lower member of the Como Conglomerate Formation, Gonfolite Lombarda Group, Southern Alps, Italy) represents the first coarse clastic inputs into the Oligocene Southalpine Foredeep. A number of techniques including sedimentary lithofacies analyses, clast counts on turbidite conglomerate bodies, sandstone petrography through Gazzi–Dickinson point‐count method and XRF analyses, and optical and minero‐chemical analyses on single clasts have been performed, in order to better define the sediment source area and geodynamic conditions which promoted sedimentation in the Southalpine Foredeep at the end of the Oligocene. The Villa Olmo Conglomerate interdigitates with the upper part of the Chiasso Formation, and gradually passes upward into the overlying Como Conglomerate Formation. Provenance analyses (conglomerate clast counts and sandstone petrography) reveal a strong metamorphic provenance signal, likely sourced from eroded Southalpine basement. An increase in igneous plutonic clasts reflects sediment supply from the Southern Steep Belt and a decrease of volcano‐sedimentary Mesozoic cover sequences. Optical and minero‐chemical analyses on volcanic detritus detect the presence of sub‐intrusive to effusive, andesite to rhyolite products, ascribable to the Varese‐Lugano Permian volcanoclastic suite, as well as Oligocene andesite products. Plutonic clasts document the presence of tonalites, granites, and brittle deformed granodiorites (with two micas), being likely sourced from the tonalite tail of the Bergell Pluton and the plutonic units of the Bellinzona‐Dascio Zone. The identification of this provenance suite implies palaeo‐drainage from the region between Varese (Southern Alps) and the Bellinzona‐Dascio Zone (Central Alps). The Villa Olmo Conglomerate is the first depositional record of the onset of tectonically driven erosion in the Alpine belt. We infer that the previous low sediment budget regime (Eocene–Middle Oligocene) was a consequence of a tectonically controlled melting phase, during which tectonic events promoted magmatic production in the middle crust of the Central Alps at rates higher than those of crustal deformation, so inhibiting sediment production. We conclude that changes in the deep structures of the Alpine Orogenic chain have controlled the main geodynamic processes during Oligocene–Neogene times, and have controlled sediment composition and supply into the Southalpine Foredeep. Copyright © 2015 John Wiley & Sons, Ltd.     

兰州地热资源赋存特征浅析

根据勘探孔资料分析,兰州盆地地热资源属于中低温沉积盆地型地热资源,其分布位置主要受盆地南北两条大断裂控制。热盖层为巨厚的第三系泥岩、砂质泥岩;热储层为第三系砂岩和白垩系砂砾岩。地温与地层岩性和深度有关,细颗粒地层导热性差,粗颗粒地层导热性好,深度越大地温越高。