山东玲珑和郭家岭岩体的同位素年龄及其地质意义

本文采用~(40)K-Ar/~(39)Ar快中子活化和K-Ar稀释法定年技术对玲珑岩体和郭家岭岩体进行了年龄测定。~(40)Ar/~(39)Ar阶段加热年龄谱表明,玲珑岩体和郭家岭岩体的坪年龄分别为164.2±0.7Ma和134.8±1.7Ma,其形成时代同属燕山期,为同一成因不同阶段的产物。同位素年龄提供的数据支持了两岩体为交代混合岩化的成因观点。~(40)Ar/~(39)At和K-Ar年龄结果还表明:角闪石和黑云母均是~(40)Ar/~(39)Ar理想定年矿物,对K-Ar法而言,角闪石最理想,黑云母次     

天山古生代增生造山作用及其构造转换事件

天山造山带自新元古代以来，经历了漫长而复杂的俯冲增生造山作用和陆内构造活化过程，属于典型的复合型造山带。基于近年研究进展，本文对伊犁、境内外中天山和南天山构造带前寒武纪基底、古生代沉积序列、多期陆缘弧岩浆岩和构造缝合带的变形变质特征、形成环境和年代学等进行了总结分析，梳理了天山古生代增生造山作用中的三次重要构造转换事件及其地质记录。① 伊犁南北两缘、中天山、南天山和塔里木北缘，均发育中奥陶世—志留纪的大陆弧岩浆作用，伊犁北缘、南天山 塔里木北部早古生代沉积环境发生显著变化，表明天山 塔里木北缘在中—晚奥陶世发生了从被动陆缘向活动陆缘的转换。② 伊犁南、北两缘和中天山的早古生代岩层在晚志留世—早泥盆世普遍发生了强烈的韧性变形和角闪岩相变质作用，其上不整合覆盖有弱变形未变质的晚泥盆世—石炭纪火山 沉积地层；该区域不整合是哈萨克斯坦微大陆拼合事件在研究区的构造响应，也标志着准噶尔洋和南天山洋的俯冲方式在泥盆纪发生了由前进式（东太平洋型）向后撤式（西太平洋型）的构造转换，导致伊犁和中天山在晚泥盆世—石炭纪经历了伸展背景下的大陆弧岩浆作用，在南天山 塔里木北缘则形成了一系列弧后有限洋盆。③ 天山各构造单元及其边界缝合带中普遍发育晚石炭世逆冲推覆构造和二叠纪走滑韧性剪切带、晚石炭世—早二叠世滑塌堆积和二叠纪后造山岩浆岩，指示晚石炭世—早二叠世发生了由汇聚造山向陆内构造的转换。这些构造转换事件是认识古亚洲洋各分支洋盆从初始俯冲、俯冲方式转换到俯冲终结过程的基础，也是探讨增生造山动力学的关键。     

Conditions for veining in the Barrandian Basin (Lower Palaeozoic), Czech Republic: evidence from fluid inclusion and apatite fission track analysis

The interplay between fracture propagation and fluid composition and circulation has been examined by deciphering vein sequences in Silurian and Devonian limestones and shales at Kosov quarry in the Barrandian Basin. Three successive vein generations were recognised that can be attributed to different stages of a basinal cycle. Almost all generations of fracture cements host abundant liquid hydrocarbon inclusions that indicate repeated episodes of petroleum migration through the strata during burial, tectonic compression and uplift.The earliest veins that propagated prior to folding were displacive fibrous “beef” calcite veins occurring parallel to the bedding of some shale beds. Hydrocarbon inclusions within calcite possess homogenisation temperatures between 58 and 68 °C and show that the “beef” calcites originated in the deeper burial environment, during early petroleum migration from overpressured shales.E–W-striking extension veins that postdate “beef” calcite formed in response to Variscan orogenic deformations. Based on apatite fission track analysis (AFTA) data and other geological evidence, the veins probably formed 380–315 Ma ago, roughly coinciding with peak burial heating of the strata, folding and the intrusion of Variscan synorogenic granites. The veins that crosscut diagenetic cements and low-amplitude stylolites in host limestones are oriented semi-vertically to the bedding plane and are filled with cloudy, twinned calcite, idiomorphic smoky quartz and residues of hardened bitumen. Calcite and quartz cements contain abundant blue and blue–green-fluorescing primary inclusions of liquid hydrocarbons that homogenise between 50 and 110 °C. Geochemical characteristics of the fluids as revealed by gas chromatography–mass spectrometry, particularly the presence of olefins and parent aromatic hydrocarbons (phenonthrene), suggest that the oil entrapped in the inclusions experienced intense but geologically fast heating that resulted in thermal pyrolysis of its hydrocarbons. This implies that the organic fluids in the fractures may have been partly influenced by heating associated with igneous intrusions that are hidden below the surface.Subvertical N–S-striking veins represent the most recent fracturing event(s). Some of these veins are only a few millimeters thick and sparsely mineralised with thin leaf-like quartz crystals that contain tiny blue and yellow–orange-fluorescing hydrocarbon inclusions. Most of the N–S veins, however, occur as thick calcite veins that generally crystallised at 70 °C or less from H₂O–NaCl solutions of variable salinity with admixture of petroleum. The origin of these fluids is interpreted in terms of deeply circulating meteoric waters that partially mixed with deep basinal fluids. Wider structural considerations combined with fission-track analysis of adjacent host sediments suggest that N–S veins formed during post-Mesozoic uplift of the area, probably in response to major Tertiary Alpine deformations transmitted far into the Bohemian Massif.     

福建省区域地质构造特征

福建自晚太古代以来经受了多次造山运动影响，尤以燕山期构造—岩浆活动最为强烈和频繁，以致省内华夏古陆不断发生裂解及增生。省内的北北东—北东东、北西—东西及南—北走向断裂十分发育，形成大小不同的断块（地体）。最突出的是南平—宁化（北东）断裂带与政和—大埔（北北东）构造—岩浆带相交汇，将福建省割切为闽西北、闽西南及闽东３个地体。本文对主要断裂及三大地体的构造—岩浆活动、变质—变形、岩浆侵入与喷发、地体的分离与拼接的演化历史进行概略阐述。总之，福建省是经多期造山作用由不同地体或断块拼接而成的复合造山带     

秦岭大别碰撞造山带根部结晶基底隆升的变质岩石学证迹

秦岭大别碰撞造山带中隆升最高的结晶基底便是大别杂岩，在超高压变质岩和某些高级变质岩中均发现典型的近等温减压（ＩＴＤ）型的退变质结构，多呈后成合晶或冠状体的形式取代或包绕原生矿物晶粒（主晶），显示退变质不平衡反应的过程．然而超高压变质岩与大别杂岩中的高级变质岩，变质地温梯度截然不同，暗示它们形成的构造条件极不相同，超高压变质岩早期由岩石圈深处（１２０ｋｍ±）折返到下地壳与那里的高级变质岩构造混合，平行并置，而后才一起隆升．退变质不平衡结构与寄主岩的面理无关，说明这种近等温的减压退变质作用发生于后造山时期近绝热条件下的隆升体制，近绝热隆升的热源可能是中生代以来大别山地区岩石圈减薄所引起     

论造山运动的时间特征

造山运动是指会聚板块边缘岩石圈构造加厚形成山带的过程,对其时间特征的认识历来存有争议。造山带变形构造研究表明,逆冲断裂是控制造山带发展、演化的主要变形机制,逆冲断裂扩展的方向性、序次性和长期性使笔者确信,造山运动是一个延续可达几十百万年的长期、分阶段的发展过程。造山运动发展阶段性主要表现为主逆冲断裂带的转换和变形速率的变化。角度不整合形成机制和空间转换规律分析进一步证实了上述认识。“长期性”和“阶段性”是造山运动时间特征的两个不可分割的侧面。前陆盆地是研究造山运动的关键地区之一。     

Three-dimensional numerical simulations of crustal deformation and subcontinental mantle convection

3-D simulations of mantle convection allowing for continental crust are explored to study the effects of crustal thickening on lithosphere stability and of continents on large-scale mantle flow. Simulations begin with a crustal layer within the upper thermal boundary layer of a mantle convection roll in a 1 × 1 × 1 Cartesian domain. Convective stresses cause crust to thicken above a sheet-like mantle downwelling. For mild convective vigor an initial crustal thickness variation is required to induce 3-D lithospheric instability below the zone of crustal convergence. The amplitude of the required variation decreases with increasing convective vigor. Morphologically, instability is manifest in formation of drip-like thermals that exist within the large-scale roll associated with initial crustal thickening. A strong surface signature of the drips is their ability to cause deviations from local Airy compensation of topography. After the initial thickening phase, the crustal accumulation that forms serves as a model analog to a continent. Its presence leads to mantle flow patterns distinctly different from the steady-state roll that results in its absence. Large lateral thermal gradients are generated at its edge allowing this region to be the initiation site for continued small-scale thermal instabilities. Eventually these instabilities induce a restructuring of large-scale mantle flow, with the roll pattern being replaced by a square cell. Although preliminary and idealized, the simulations do show the fluid dynamical plausibility behind the idea that significant mantle variations can be generated along the strike of a largely 2-D mountain chain by the formation of the chain itself. The ability of a model continent to cause a change in fundamental convective planform also suggests that the effects of continental crust on mantle convection may be low-order despite the seemingly trivial volume of crust relative to mantle.     

秦岭造山带泥盆系热水沉积岩相应用研究及实例

构造-热水沉积岩相与盆地的古地理环境,热水沉积岩相与热水沉积成矿,热 (水 )流体岩相与构造背景、构造古地理,它们之间有密切地内在联系.应用热水沉积岩相、沉积相及沉积体系分析方法,对凤县铅硐山-双石铺三级构造热水成矿盆地进行研究.     

再论陆内型造山作用

目前流行的半真实、半虚假的新全球构造学说已经给中国大陆地质研究带来一定的困惑和困难。中国大陆各地质时代发生的造山作用皆属陆内型。用地体说、碰撞说、地缝合线说和安第斯造山模式论述青藏高原的形成、演化史是地质研究的几个误区。秦岭-大别山属陆内型造山带,其形成与板块构造无关,采用壳-幔拆离构造的造山机制可解释超高压变质岩的生成。超高压变质岩是识别岩石圈收缩引起的一系列地质事件最有效的标志。     

Geochronology of the mid-German crystalline rise west of the River Rhine

The mid-German crystalline rise has its westernmost exposures at the western margin of the Rhine graben in the southern Pfalz and the northern Alsace. The outcrops are made up of granitoid rocks and minor volcano-sedimentary sequences. Radiometric ages obtained by U/Pb, Pb/Pb, Sm/Nd and Rb/Sr analyses of the igneous rocks from this area range from ∼433 to ∼325 Ma thus covering a time span from the Silurian to the end of the lower Carboniferous. Because the investigated rocks are — according to their chemical composition — largely related to subduction zone environments, the following three geodynamical scenarios are postulated, always taking subduction of oceanic crust beneath the mid-German crystalline rise into account: (a) subduction of the Rheic ocean during the Silurian from the north; (b) subduction of the Rhenohercynian ocean during the late Devonian (∼369 Ma) from the north; (c) subduction of the Saxothuringian ocean during the lower Carboniferous (∼334 Ma) from the south.