试论板缘仰冲作用及其对板内构造的影响

板块学说发展史上存在着造山作用的仰冲和俯冲两种成因观点。俯冲说难以解释中脊俯冲、板缘构造、板内变形及海沟构造。仰冲说认为板块会聚边缘处在两个相向运动着的对流系交会带。根据板缘构造平、剖面特点,结合威尔逊旋回、板块运动史、地壳结构等分析,大陆仰冲板块是在克服属弱对流系一方的洋板块的抵抗,迫使贝尼奥夫带不断向洋退却过程中向前推进.而造成各种板缘和板内构造的变形机制的。据此,提出一个断续仰冲模式以代替传统的连续俯冲模式。用仰冲观点分析了形成板内变形的内、外条件和常见的变形型式。还试用板内仰冲作用来解释华南加里东期构造特点与钦州地槽之谜。     

华北燕山带东部三叠纪和侏罗纪大地构造演化：来自备受争议的邓杖子组及相邻地层的线索

位于辽西凌源市南部的牛营子-邓杖子地区侏罗系地质问题多年来困扰着地质学家。争论最多的构造形迹是一套平面上呈狭长矩形,以断层为界的近直立中元古界常州沟组石英岩,及局部长城系顶部地层。这套地层绵延35 km,呈北北东展布。其西界为近直立的大齐子断层（新命名断层）和大部分向东倒转的陡倾下侏罗统邓杖子组;东界为近直立的朱杖子断层（新命名断层）和西倾的中侏罗统郭家店组。前人的构造解释倾向于大齐子断层为邓杖子组一侧下降的陡倾正断层,朱杖子断层为郭家店组一侧下降的陡倾逆断层。文中不同意这样的解释,并发现有证据表明上述两个断层都形成于之前尚未识别出的侏罗纪构造事件时期。将大齐子断层解释为早侏罗世晚期-中侏罗世早期形成的一条向西逆冲的断层,沿着它使长城系推覆于邓杖子组之上,然后,该逆冲断层上、下盘地层共同卷入后期褶皱变形当中。朱杖子断层原本为正断层,形成于原来未识别出的中侏罗世伸展变形阶段,并构成了郭家店半地堑边界断层。朱杖子断层沿着向东倾斜的常州沟组石英岩与串岭沟组页岩的界面发育。随着断层的发育,位于常州沟组石英岩之上的串岭沟组及长城系上部地层发生拆离沉降并被埋藏在半地堑之下。随后,发生在中侏罗世晚期或晚侏罗世早期收缩构造变形,改造了邓杖子-常州沟-郭家店组构造组合的几何形态。本期改造导致以下结果：（1）朱杖子正断层发生反转成为逆断层;（2）蓟县系沿着杨杖子-瓦房店逆冲断层向东掩覆于断层围限的长城系地层及相邻侏罗系之上。同时,邓杖子组倾角加大并向东倒转。研究表明,辽西地区的侏罗纪构造演化过程远比原先所认为的要复杂。     

华北地块中部新构造运动

由于印度板块持续向北运动,引起青藏高原的挤出,并于中新世末引起华北地块的向东挤出。大约在7.3 Ma,太行山西侧渭河盆地唐县面首先解体,继而向北、向东发展;到5 Ma左右,太行山东麓断裂带的右行走滑,导致华北中部唐县面全面解体,形成多个太行山内部山间盆地,以及太行山西侧山西地堑系。这些断陷盆地的断陷幅度各不相同,太行山西侧山西地堑系断陷幅度较大,太行山内部山间盆地断陷幅度较小,太行山东部的渤海湾盆地断陷活动不明显。伴随着盆地的形成,太行山相对进入快速隆升阶段。山西地堑系控盆断裂以及太行山东麓断裂带第四纪以来仍存在明显活动,切割并控制第四系,局部在地表形成地裂缝。华北地块中部的应力场恢复以及深部构造分析表明,深部地幔上涌对浅部伸展构造的形成具有重要的影响,深部构造演变与浅部构造演变具有高度的一致性和耦合性。太行山东部渤海湾盆地自中新世以来就进入拗陷阶段,断裂活动弱,构造演化与西侧差异较大,表明这期构造运动动力源于西侧,太行山东麓断裂带作为两侧差异演变的边界,调节着两侧的差异构造活动。     

The electrical structure of the Slave craton

The Slave craton in northwestern Canada, a relatively small Archean craton (600×400 km), is ideal as a natural laboratory for investigating the formation and evolution of Mesoarchean and Neoarchean sub-continental lithospheric mantle (SCLM). Excellent outcrop and the discovery of economic diamondiferous kimberlite pipes in the centre of the craton during the early 1990s have led to an unparalleled amount of geoscientific information becoming available.

Over the last 5 years deep-probing electromagnetic surveys were conducted on the Slave, using the natural-source magnetotelluric (MT) technique, as part of a variety of programs to study the craton and determine its regional-scale electrical structure. Two of the four types of surveys involved novel MT data acquisition; one through frozen lakes along ice roads during winter, and the second using ocean-bottom MT instrumentation deployed from float planes.

The primary initial objective of the MT surveys was to determine the geometry of the topography of the lithosphere–asthenosphere boundary (LAB) across the Slave craton. However, the MT responses revealed, completely serendipitously, a remarkable anomaly in electrical conductivity in the SCLM of the central Slave craton. This Central Slave Mantle Conductor (CSMC) anomaly is modelled as a localized region of low resistivity (10–15 Ω m) beginning at depths of 80–120 km and striking NE–SW. Where precisely located, it is spatially coincident with the Eocene-aged kimberlite field in the central part of the craton (the so-called “Corridor of Hope”), and also with a geochemically defined ultra-depleted harzburgitic layer interpreted as oceanic or arc-related lithosphere emplaced during early tectonism. The CSMC lies wholly within the NE–SW striking central zone defined by Grütter et al. [Grütter, H.S., Apter, D.B., Kong, J., 1999. Crust–mantle coupling; evidence from mantle-derived xenocrystic garnets. Contributed paper at: The 7th International Kimberlite Conference Proceeding, J.B. Dawson Volume, 1, 307–313] on the basis of garnet geochemistry (G10 vs. G9) populations.

Deep-probing MT data from the lake bottom instruments infer that the conductor has a total depth-integrated conductivity (conductance) of the order of 2000 Siemens, which, given an internal resistivity of 10–15 Ω m, implies a thickness of 20–30 km. Below the CSMC the electrical resistivity of the lithosphere increases by a factor of 3–5 to values of around 50 Ω m. This change occurs at depths consistent with the graphite–diamond transition, which is taken as consistent with a carbon interpretation for the CSMC.

Preliminary three-dimensional MT modelling supports the NE–SW striking geometry for the conductor, and also suggests a NW dip. This geometry is taken as implying that the tectonic processes that emplaced this geophysical–geochemical body are likely related to the subduction of a craton of unknown provenance from the SE (present-day coordinates) during 2630–2620 Ma. It suggests that the lithospheric stacking model of Helmstaedt and Schulze [Helmstaedt, H.H., Schulze, D.J., 1989. Southern African kimberlites and their mantle sample: implications for Archean tectonics and lithosphere evolution. In Ross, J. (Ed.), Kimberlites and Related Rocks, Vol. 1: Their Composition, Occurrence, Origin, and Emplacement. Geological Society of Australia Special Publication, vol. 14, 358–368] is likely correct for the formation of the Slave's current SCLM.     

地质基础理念之我见

任-侵位的岩浆体，在结晶分异、固化成岩过程中，一般都可分为：已结晶的固相岩体、正(半)结晶的可塑相岩体及未结晶的熔融相岩浆3部分．此时，若发生了地壳运动，地壳运动的构造作用力。使正(半)结晶的可塑相岩体发生可塑相变形，形成片麻化岩体；地壳运动(包括地震)时的构造作用力为脉动性质的挤压作用力；岩体发生片麻化的地壳运动，又使已结晶的固相岩体和围岩发生断裂活动，形成了断裂带控矿、容矿构造；未结晶的熔融相岩浆再度上升侵位，便形成了小侵入岩体控矿构造．残浆的形成与排出，控矿构造的发生、发展与控矿过程，都是在这次地壳运动过程中完成的．因此，对这次地壳运动可称成矿作用．     

Coastal neotectonics in Southern Central Andes: uplift and deformation of marine terraces in Northern Chile (27°S)

Neotectonic observations allow a new interpretation of the recent tectonic behaviour of the outer fore arc in the Caldera area, northern Chile (27°S). Two periods of deformation are distinguished, based on large-scale Neogene to Quaternary features of the westernmost part of the Coastal Cordillera: Late Miocene to Early Pliocene deformations, characterized by a weak NE–SW to E–W extension is followed by uppermost Pliocene NW–SE to E–W compression. The Middle Pleistocene to Recent time is characterized by vertical uplift and NW–SE extension. These deformations provide clear indications of the occurrence of moderate to large earthquakes. Microseismic observations, however, indicate a lack of shallow crustal seismicity in coastal zone. We propose that both long-term brittle deformation and uplift are linked to the subduction seismic cycle.     

渭河断裂带的构造演化与地震活动

渭河断裂带在前新生代为一条分割基底的古超壳断裂,新生代转为铲式伸展断裂,其伸展拉伸掀斜作用形成了渭河盆地的雏形,现代以引张倾滑兼枢纽运动为特征。该断裂带为渭河盆地一条最显著的地震活动带,自公元前280年以来有20次5级以上地震与该断裂带有关     

中国板块构造与盐类矿产

中国大陆的华北、塔里木、准噶尔－兴安、华南及甘青藏等五大板块发展过程中于地块边缘活动带、陆间裂谷、陆内裂谷等场所生成的含盐盆地，沉积了各时期（Ｏ、Ｃ、Ｔ、Ｊ－Ｅ和Ｑ）盐类矿床。通过分析对比认为，甘青藏板块兰坪－思茅拗陷带（Ｊ２－Ｅ１、Ｑ），塔里木板块（Ｃ、Ｋ－Ｅ、Ｑ），华北板块（Ｏ２），华南板块（Ｔ１－２）为成钾有利地带，中国东部众多的Ｋ－Ｅ红层盆地中成钾条件较差     

柴达木盆地英雄岭地区新生代构造演化动力学特征

通过分析柴达木盆地英雄岭 (YL)地区地质、2D/ 3D地震、遥感、重磁电和钻探等资料 ,提出了喜马拉雅运动几个阶段在该区的构造动力学响应特征。研究认为喜马拉雅运动晚期 ,英雄岭地区西南侧的阿卡腾能山因近SN向的区域挤压作用 ,产生了顺时针方向的旋转及隆升作用 ,从而在干柴沟一带形成了强烈的SE向局部挤压应力场 ,基底大幅隆升 ,而在英雄岭隆起的南侧则产生了局部的拉张构造环境。喜马拉雅山中期运动在该区的主要表现形式就是使古近纪的张扭构造环境转变为新近纪的坳陷构造环境 ,英雄岭西南的阿尔金地区发生隆升作用 ,沉积中心发生向东和向北的迁移。通过分析主干断裂、构造块体和沉积凹陷的分布特征等 ,得出喜马拉雅早期英雄岭及邻区发育局部拉张环境 ,为较为稳定的断陷湖盆发育期 ,沉积了一套优质烃源岩。英雄岭地区潜在勘探领域主要有构造裂缝型圈闭、地层岩性圈闭及渐新世断凸构造圈闭等。     

Tectonic evolution of the ultrahigh-pressure (UHP) and high-pressure (HP) metamorphic belts from central China

Abstract In the Triassic suture between the Sino-Korean and Yangtze cratons, the Dabie metamorphic Complex in central China includes three tectonic units: the northern Dabie migmatitic terrane, the central ultrahigh-P coesite- and diamond-bearing eclogite belt, and the southern high-P blueschist-eclogite belt. This complex is bounded to the north by a north-dipping normal fault with a Paleozoic accretionary complex and to the south by a north-dipping reverse fault with Yangtze basement plus its foreland fold-and-thrust sequence. Great differences in metamorphic pressure suggests that these units reached different depths during metamorphism and their juxtaposition occurred by wedge extrusion of subducted old continental fragments. These units were subsequently subjected to (i) Barrovian type regional metamorphism and deformation at shallow depths; (ii) intrusion of Cretaceous granitic plutons; and (iii) doming and segmentation into several blocks by normal and strike-slip faults. A new speculative model of tectonic exhumation of UHP rocks is proposed.