大陆岩石圈对扩张机制的响应——辽蒙地质走廊中—新生代火山活动的时空分布

选择以辽西为中心,近东西向延伸800km的辽蒙地质走廊为研究区,通过年代学研究,确认130Ma以来的中、新生代火山活动对称分布的时空格局具有“中间老、两侧新”的特点,而且随着时间的推移,软流圈来源的岩浆向东西两侧侧向流动,岩浆来源不断加深。在此基础上提出“软流圈底辟体上涌和水平侧向流动”的模式。     

大陆岩石圈对扩张机制的响应—辽蒙地质走廊中—新生代火山活动的时空分布

选择辽西为中心,以近东西向延伸800km的辽蒙地质走廊为研究区,通过年代学研究,确认130Ma以来的中、新生代火山活动对称分布的时空格局,具有“中间老、两侧新”的特点,而且随着时间的推移,软流圈来源的岩浆向东西两侧侧向流动,岩浆来源不断加深。在此基础上提出“软流圈底辟体上涌和水平侧向流动”的模式。     

辽西及邻区中-新生代火山岩的时空对称分布及其启示

辽西中生代火山活动之后,老第三纪、新第三纪和第四纪玄武岩的喷溢依次向东、西两侧对称扩展,其范围从内蒙古阿巴嘎至辽东宽甸,长800km。相应地,火山岩从中-酸性的粗面质岩石变成碱性玄武岩,表明岩浆来源越来越深。Sr-Nd同位素特征显示从白垩纪末到第四纪,岩浆源区从EMI型富集地幔转向亏损地幔。根据火山岩时空对称分布的格局,本文提出了两个值得深入研究的问题:大陆板块与大洋板块的扩张与增生方式为什么不同?辽西乃至中国东部有小型地幔柱存在的可能性吗?     

中国大陆岩石圈岩石学结构、类型与不均一性

根据中国大陆的地质特征和现今地球物理特征,区分不同地区的岩石圈类型;依据岩石学方法、地球演化模型、地震波速与成分的关系等综合方法,建立了相应类型岩石圈的岩石学结构;根据岩石圈的动力学性质,划分出中国大陆克拉通、造山带、裂谷、边缘海洋壳和岛弧等5大岩石圈类型,首次构建出中国大陆岩石圈岩石学结构模型,展示了中国大陆岩石圈的不均一特征。     

Formation and evolution of Precambrian continental lithosphere in South China

An overview is presented for the formation and evolution of Precambrian continental lithosphere in South China. This is primarily based on an integrated study of zircon U–Pb ages and Lu–Hf isotopes in crustal rocks, with additional constraints from Re–Os isotopes in mantle-derived rocks. Available Re–Os isotope data on xenolith peridotites suggest that the oldest subcontinental lithospheric mantle beneath South China is primarily of Paleoproterozoic age. The zircon U–Pb ages and Lu–Hf isotope studies reveal growth and reworking of the juvenile crust at different ages. Both the Yangtze and Cathaysia terranes contain crustal materials of Archean U–Pb ages. Nevertheless, zircon U–Pb ages exhibit two peaks at 2.9–3.0 Ga and ~ 2.5 Ga in Yangtze but only one peak at ~ 2.5 Ga in Cathaysia. Both massive rocks and crustal remnants (i.e., zircon) of Archean U–Pb ages occur in Yangtze, but only crustal remnants of Archean U–Pb ages occur in Cathaysia. Zircon U–Pb and Lu–Hf isotopes in the Kongling complex of Yangtze suggest the earliest episode of crustal growth in the Paleoarchean and two episodes of crustal reworking at 3.1–3.3 Ga and 2.8–3.0 Ga. Both negative and positive ε_Hf(t) values are associated with Archean U–Pb ages of zircon in South China, indicating both the growth of juvenile crust and the reworking of ancient crust in the Archean. Paleoproterozoic rocks in Yangtze exhibit four groups of U–Pb ages at 2.1 Ga, 1.9–2.0 Ga, ~ 1.85 Ga and ~ 1.7 Ga, respectively. They are associated not only with reworking of the ancient Archean crust in the interior of Yangtze, but also with the growth of the contemporaneous juvenile crust in the periphery of Yangtze. In contrast, Paleoproterozoic rocks in Cathaysia were primarily derived from reworking of Archean crust at 1.8–1.9 Ga. The exposure of Mesoproterozoic rocks are very limited in South China, but zircon Hf model ages suggest the growth of juvenile crust in this period due to island arc magmatism of the Grenvillian oceanic subduction. Magmatic rocks of middle Neoproterozoic U–Pb ages are widespread in South China, exhibiting two peaks at about 830–800 Ma and 780–740 Ma, respectively. Both negative and positive ε_Hf(t) values are associated with the middle Neoproterozoic U–Pb ages of zircon, suggesting not only growth and reworking of the juvenile Mesoproterozoic crust but also reworking of the ancient Archean and Paleoproterozoic crust in the middle Neoproterozoic. The tectonic setting for this period of magmatism would be transformed from arc–continent collision to continental rifting with reference to the plate tectonic regime in South China.     

我国中新生代陆相盆地含铀沉积建造类型、特征及其研究意义

将我国中新生代陆相盆地含铀沉积建造类型划分为陆相暗色（灰色）含煤碎屑沉积建造、陆相红色（杂色）碎屑沉积建造及陆相红色含膏盐沉积建造3类,并概述其沉积特征。探讨了沉积建造研究在砂岩型铀矿科研及生产找矿方面的意义。     

渤海湾盆地中—新生代岩石圈热结构与热-流变学演化

文章主要利用中—新生代热史、地壳分层结构以及流变学参数,模拟计算渤海湾盆地中—新生代岩石圈热结构和热-流变结构演化特征。结果表明,盆地由三叠纪—侏罗纪时期的"冷幔热壳"型岩石圈热结构转变为白垩纪至今的"热幔冷壳"型岩石圈热结构。从济阳坳陷岩石圈热-流变结构演化特征来看,中生代早期上地壳上部、中地壳上部及上地幔顶部表现为厚的脆性层;早白垩世初期中地壳上部及上地幔顶部的脆性层完全转变为韧性层;晚白垩世开始,中地壳上部出现薄层的脆性层;古近纪早期中地壳上部脆性层变薄变浅;现今则除了发育上地壳上部、中地壳上部脆性层外,上地幔顶部开始在浅部发育薄的脆性层。中—新生代岩石圈总强度演化表明在早白垩世晚期和古近纪早期经历了两期减弱,中生代早期岩石圈总强度远大于中侏罗世之后的岩石圈总强度。岩石圈热-流变结构和强度演化与华北克拉通破坏过程中岩石圈厚度的变化具有良好的对应关系,从侧面反映太平洋板块俯冲和回撤导致华北克拉通东部破坏的地球动力学过程。因此,岩石圈热-流变结构可以为盆地形成、大陆边缘和造山带等的动力学演化过程研究提供科学依据。     

中国大陆岩石圈壳幔韧性剪切带系统

众多地震测深剖面的地质构造解析显示,大陆岩石圈存在既有显著差异又有密切联系的两套断裂系统,即以地壳表层脆性剪切带为主的浅层断裂系统和以切割莫霍界面的壳幔韧性剪切带为主的深部断裂系统。根据地震测深速度结构特征,结合深部构造岩石地球化学的综合研究,将切割莫霍界面或壳幔过渡带的壳幔韧性剪切带划分为三类(俯冲带、缝合带和剪切带)五型(大陆岩石圈边缘海沟俯冲带、大陆岩石圈碰撞缝合带、挤压型壳幔韧性剪切带、伸展型壳幔韧性剪切带和走滑型壳幔韧性剪切带)。建立起中国大陆岩石圈构造变形由地壳表层向深部扩展以及由壳幔过渡带向地壳中上部扩展的岩石圈双向扩展模式。壳幔韧性剪切带既是无机成因天然气等深部流体的通道,又是地震活动区的发震构造之一,因此研究大陆岩石圈壳幔韧性剪切带具有重要学术价值和实际意义。     

Pocho volcanic rocks and the melting of depleted continental lithosphere above a shallowly dipping subduction zone in the central Andes

The Late Miocene (7.9 to 4.5 Ma) Pocho volcanic field in Argentina occurs 700 km east of the Chile trench over the modern shallowly dipping Andean Wadati-Benioff zone near 32° S latitude in Argentina. The field is located in the Sierra de Cordoba which is the easternmost Laramide-style, block-faulted range in the Sierras Pampeanas (Pampean ranges). The arrival of the shallowly dipping slab initiated both volcanism and the uplift of the Sierra de Cordoba. Pocho rocks (52% to 68% SiO₂; FeO^*/MgO>2.2) comprise an older (7.5±0.5 Ma) high-K and a younger (5.3±0.7 Ma) shoshonitic series. Mineralogic data and fractionation models show that crystallization occurred under hydrous, oxidizing conditions, which were most extreme in the high-K series. An unusual pattern of successively lower REE at higher SiO₂ concentrations can be modeled by sphene, apatite and amphibole removal. An arc-like trace element signature attributed to an arc component is strongest in the younger shoshonitic series. An important depleted lower crustal/mantle lithospheric source component in both series is indicated by non-radiogenic Sr and Pb isotopic ratios at _Nd= 0 to + 2, low Rb/Sr ratios, and low U and Th concentrations. This depleted signature contrasts with the enriched one in potassic back-arc Central Volcanic Zone (CVZ) lavas over the steeper subduction zone to the north and is attributed to several processes in the shallow subduction zone. First, deep crustal (MASH) processes in the nearly normal thickness crust beneath Pocho incorporated depleted Proterozoic basement components, and not complexly mixed structurally thickened crustal components as in the CVZ. Second, the association of Pocho volcanism with the arrival of the slab allowed little time for modification of the mantle by subduction components. Third, Miocene shallowing of the subduction zone beneath the flat-slab required thinning of both the astenosphere and the subcontinental lithosphere. Thus, an important subcrustal component could be from blocks removed from the base of the lithosphere to the west and recycled into the asthenosphere. Similar magmatic sources would have existed during Laramide shallow subduction in western North America.Deceased     

Rheology of the continental lithosphere: Progress and new perspectives

While the surface of Tibet is undergoing pervasive pure shear, stable terranes, straddling subsurface sutures, remain in the sub-continental lithospheric mantle (SCLM), attesting to its strength. Furthermore, sub-horizontal, cohesive remnant of Indian SCLM is traced northward from the Himalayan deformation front for about 600 km, exemplifying the longevity of buoyant, strong SCLM of Archean shields. Bimodal distribution of earthquake depths, with peaks concentrating in the upper/middle crust and near the Moho, has been a longstanding evidence for strong SCLM. Recent results from the Himalayas—Tibet and along the East African rift system not only corroborate the bimodal distribution but also firmly established that large earthquakes occur below the Moho. Intriguingly, non-volcanic tremors—newly discovered mode of elastic strain release—also occur near the Moho but well below the seismogenic zone in the upper/middle crust. Considering recent field observations and laboratory experiments of viscosity contrast across the Moho, the SCLM must be strong enough to accumulate elastic strain, a prerequisite for earthquakes, over geological time. Moreover, under laboratory conditions, recent advances that link the termination of frictional instability, an analogue for earthquakes, and the onset of crystal plasticity, provided a physical basis for limiting temperatures of crustal (~ 300-400 °C) and mantle (~ 600-700 °C) earthquakes. While any single rheological model cannot possibly account for all tectonic settings (which also evolve with time), lithological contrast across the Moho is important in shaping the bimodal distribution of strength in the continental lithosphere.     

木吉村斑岩铜矿成矿作用:华北克拉通中生代岩石圈减薄的响应

木吉村铜(钼、金)矿位于华北克拉通太行山北段中生代岩浆岩带,为大型隐伏斑岩型矿床.矿体赋存于侏罗纪髫髻山组与火山岩相关的闪长玢岩次火山岩相中.木吉村髫髻山组安山岩中岩浆锆石的两组U-Pb年龄分别为(150.5±3.0) Ma和(140.8±3.0) Ma,与北京西山髫髻山组火山岩锆石U-Pb年龄范围(156.6～137...     

江达—维西陆缘火山弧的形成演化及成矿作用

江达-维西陆缘火山弧为金沙江弧后洋盆向西俯冲消减和斜向碰撞过程中形成,其过程经历了俯冲造弧-碰撞成弧-张裂成盆的复杂发展历史。早二叠世晚期—晚二叠世(P₁²-P₂)形成俯冲型弧火山岩,早中三叠世(T₁₊₂)形成碰撞型弧火山岩,晚三叠世早期(T₃¹)于裂谷盆地中发育“双峰式”火山岩。晚三叠世早期(T₃¹)裂谷盆地从北向南形成生达-车所-鲁麻弧后盆地、徐中-鲁春-红坡上叠(弧后)裂谷盆地和箐口塘-催依比-上兰上叠(弧后)裂谷盆地三个次级半深海-深海盆地。生达-车所-鲁麻弧后盆地的拉裂时间为11.6 Ma,速度为0.27cm/a,距离为63km;徐中-鲁春-红坡上叠(弧后)裂谷盆地的拉裂时间为16.1 Ma,速度为0.43cm/a,距离为140km;箐口塘-催依比-上兰上叠(弧后)裂谷盆地的拉裂时间16.1 Ma,速度为0.36cm/a,距离为116km。弧火山岩中形成有沉积-改造型铜、金、银、铅、锌多金属矿,裂谷(火山)盆地中形成有喷流-沉积型铜、金、银、铅、锌多金属矿。晚三叠世早期火山-沉积盆地已成为三江地区中生代重要的成矿盆地。