论中国含油气区的构造环境性质、分区及其成油气专属性

在前中生代,形成了华北、扬子和塔里木等较大的海相及海陆交互相含油气区（盆地）,构造格架呈南北分异。经海西-印支运动,形成统一的中国大陆板块,且整体构造格架演变为东西分异。根据盆地结构、构造变形样式、岩浆活动、地温场、壳幔结构及壳幔连通程度等方面的特征,论述了中、新生代中国含油气区的大地构造环境性质与含油气特征。据此划分出 4个具有不同构造环境性质的含油气区：①东部裂谷伸展区,其西带为华夏裂谷系,以产下第三系和白垩系原油为主,东带为大陆架裂谷系,以产下第三系煤型气为主;②中部克拉通构造稳定区,以产古生界天然气为主;③西北构造反转区,含油气层系较多,油气成因类型也多样;④特提斯碰撞-走滑区,构造变形复杂,部分地区具有较好的油气资源前景。进一步讨论了油气形成的"构造环境专属性"问题。     

华北克拉通北部地区古-中元古代富碱侵入岩年代学及意义

本文报道华北克拉通北部燕辽三叉裂堑系和辽-吉拗拉谷内一系列古-中元古代富碱侵入岩的锆石U-Pb年龄。这些岩体整体呈近东西向分布，与该地区同期发育的其他非造山球斑花岗岩、斜长岩和大红裕组火山岩都形成于拉张性构造环境，并构成了一条长近千公里的迄今国内外最古老的富碱侵入岩带。该富碱侵入岩带具有东部较老（〉1．8Ga）和西部年轻（1．7Ga左右）的特点，它提供了华北克拉通在1．85—1．70Ga期间处于裂解构造格局的最好证据，丰富了全球性前寒武纪超大陆裂解的研究内容。     

What Happened in the Trans-North China Orogen in the Period 2560-1850 Ma？

The Trans-North China Orogen （TNCO） was a Paleoproterozic continent-continent collisional belt along which the Eastern and Western Blocks amalgamated to form a coherent North China Craton （NCC）. Recent geological, structural, geochemical and isotopic data show that the orogen was a continental margin or Japan-type arc along the western margin of the Eastern Block, which was separated from the Western Block by an old ocean, with eastward-directed subduction of the oceanic lithosphere beneath the western margin of the Eastern Block. At 2550-2520 Ma, the deep subduction caused partial melting of the medium-lower crust, producing copious granitoid magma that was intruded into the upper levels of the crust to form granitoid plutons in the low- to medium-grade granite-greeustone terranes. At 2530-2520 Ma, subduction of the oceanic lithosphere caused partial melting of the mantle wedge, which led to underplating of mafic magma in the lower crust and widespread mafic and minor felsic volcanism in the arc, forming part of the greenstone assemblages. Extension driven by widespread mafic to felsic volcanism led to the development of back-arc and/or intra-arc basins in the orogen. At 2520-2475 Ma, the subduction caused further partial melting of the lower crust to form large amounts of tonalitic-trondhjemitic-granodioritic （TTG） magmatism. At this time following further extension of back-arc basins, episodic granitoid magmatism occurred, resulting in the emplacement of 2360 Ma, -2250 Ma 2110-21760 Ma and -2050 Ma granites in the orogen. Contemporary volcano-sedimentary rocks developed in the back-arc or intra-are basins. At 2150-1920 Ma, the orogen underwent several extensional events, possibly due to subduction of an oceanic ridge, leading to emplacement of mafic dykes that were subsequently metamorphosed to amphibolites and medium- to high-pressure mafic granulites. At 1880-1820 Ma, the ocean between the Eastern and Western Blocks was completely consumed by subduction, and the dosing of the ocean led to the continent-arc-continent collision, which caused large-scale thrusting and isoclinal folds and transported some of the rocks into the lower crustal levels or upper mantle to form granulites or eclogites. Peak metamorphism was followed by exhumation/uplift, resulting in widespread development of asymmetric folds and symplectic textures in the rocks.     

Biomediation of calcrete at the gold anomaly of the Barns prospect,Gawler Craton,South Australia

Anomalously high Au concentrations (2.5 to 50 ppb) in regolith carbonate accumulations, such as calcrete and calcareous sands in aeolian sand dunes overlying Au mineralisation of the Gawler Craton, South Australia, show a marked covariance of Au with K, Mg and most notably Ca. This relationship appears to be linked to the authigenic formation of smectites and carbonates within the aeolian dunes in the region. However, little is known about the processes involved in the formation of carbonates under semi-arid and arid conditions. In this study the geochemical properties of aeolian dunes along several depth profiles of 2 to 4 m are investigated in order to assess the relationship between Au mobility and calcrete formation. In the profiles a strongly systematic relationship between Au and the increasing Ca–Mg contents at depth highlights the close association between the enrichment of Au in the calcrete and the underlying hydrothermal mineralisation. Intense calcrete formation and concurrent Au enrichment also occurs in the vicinity of roots penetrating the dune. Thin section petrography and cathodoluminescence show that most of the calcrete in the regolith profiles is micritic; some sparic crystallites have also been identified. To demonstrate the presence of microbial processes that may mediate the formation of calcrete, samples from a depth profile in the dune were taken under sterile conditions. After amendment with urea and incubation of up to 24 h, up to 18 mg/l of NH₄⁺ were detected in near surface samples. At depth of 2.3 m 1 mg/l NH₄⁺ were detected compared to a control that contained below 0.05 mg/l NH₄⁺. These results suggest that the genesis of calcrete and pedogenic carbonate in the area may be partly biologically mediated via processes such as the metabolic breakdown of urea by resident microbiota which generates a pH and pCO₂ environment conducive to the precipitation of carbonate. In the process of urea breakdown organic Au complexes such as Au-amino acid complexes may become destabilised in solution and Au may be co-precipitated, resulting in the fine, non-particulate distribution of Au throughout the micritic calcrete carbonate. In conclusion, this study suggests a coupled mechanism of biologically mediated and inorganic mechanisms that lead to the formation of Au-in-calcrete anomalies.     

大陆科学钻探先导孔（CCSD—P1）橄榄岩地幔属性及动力学意义

早中生代的扬子大陆向华北大陆的深俯冲碰撞作用以及中、新生代的华北东部岩石圈减薄作用是国际大陆动力学问题研究的两个热点。然而，把它们有机联系起来，探讨深部岩石圈演化动力学过程的研究还很少。报道了中国大陆科学钻探先导孔（CCSD-PP1）橄榄岩的矿物岩石化学分析结果。这些橄榄岩亏损玄武质组分（如低w（CaO＋Al2O3）、高Mg^#等），并经历了中元古代来自软流圈的碳酸岩熔体的交代作用和早中生代的超高压再平衡过程。结合已发表的华北捕虏体橄榄岩资料，对这一橄榄岩的原始地幔属性进行了分析。发现CCSD-PP1橄榄岩与华北古老岩石圈地幔组成相似，是早中生代来自华北岩石圈的构造侵入体。早中生代华北岩石圈的伸展减薄与苏鲁超高压变质岩石的折返提供了早期软流圈物质上涌的构造体制。     

A new key pole for the East European Craton at 1452 Ma: Palaeomagnetic and geochronological constraints from mafic rocks in the Lake Ladoga region (Russian Karelia)

Palaeomagnetic and geochronological studies on mafic rocks in the Lake Ladoga region in South Russian Karelia provide a new, reliably dated Mesoproterozoic key paleopole for the East European Craton (Baltica). U–Pb dating on baddeleyite gives a crystallisation age of 1452 ± 12 Ma for one of the studied dolerite dykes. A mean palaeomagnetic pole for the Mesoproterozoic dolerite dykes, Valaam sill and Salmi basalts yields a paleopole at 15.2°N, 177.1°E, A₉₅ = 5.5°. Positive baked contact test for the dolerite dykes and positive reversal test for the Salmi basalts and for the dykes confirm the primary nature of the magnetisation. Comparison of this Baltica palaeopole with coeval paleomagnetic data for Laurentia and Siberia provides a revised palaeoposition of these cratons. The results verify that the East European Craton, Laurentia and Siberia were part of the supercontinent Columbia from the Late Palaeoproterozoic to the Middle Neoproterozoic.     

4D architecture and tectonic evolution of the Laverton region,eastern Yilgarn Craton,Western Australia

The Laverton region, located in the eastern Yilgarn Craton (EYC) Western Australia, is second only to the Kalgoorlie region for gold endowment. The integration of high-density, potential-field data, regional- and camp-scale seismic reflection data, regional- and mine-scale structural analysis, and geochronologically-constrained stratigraphy, provided new insights into the 4D architecture and tectonic evolution of Laverton region.     

Geodynamics of the eastern Yilgarn Craton

Over the last decade there have been significant advances in our understanding of the stratigraphy, magmatism, deformation, metamorphism and timing of mineralisation, in the eastern Yilgarn Craton (EYC) of Western Australia. The integration of these disciplines has enabled a holistic review of the tectonic history of the EYC which favours a paraautochthonous tectonic model.     

贺兰山高压泥质麻粒岩——华北克拉通西部陆块拼合的岩石学证据

贺兰山孔兹岩系作为华北克拉通西部孔兹岩带的重要组成部分,其成因问题一直存在争议。近来,在对贺兰山富铝岩系研究过程中,发现了具有"蓝晶石+条纹长石+石榴石"特征组合的高压泥质麻粒岩。通过岩相观测与相平衡定量模拟,确定其曾经历四个阶段的变质演化过程,即早期进变质阶段(M1)、变质峰期阶段(M2)、峰期后降压阶段(M3)和晚期退变阶段(M4)。早期进变质阶段,以石榴石中包裹黑云母和白云母为特征。变质峰期阶段,以出现"蓝晶石+条纹长石+石榴石"组合为特征,变质温、压条件为850～870℃、1.4～1.5GPa。峰期后降压阶段以峰期石榴石和蓝晶石转变为堇青石和夕线石为特征,温压条件大致为840～860℃、0.6～0.8GPa。晚期退变阶段以出现新生黑云母为标志,温、压条件为780～810℃、0.45～0.55GPa。PT轨迹具有顺时针演化样式,峰期后表现为先发生近等温降压(ITD)、后发生近等压冷却(IBC)的退变过程,反映陆-陆碰撞发生高压麻粒岩相变质作用,后又快速折返到正常地壳深度的变质动力学过程,进而从岩石学角度证明华北克拉通西部孔兹岩带是由北部的阴山陆块与南部的鄂尔多斯陆块发生碰撞所致。