程裕淇主编《中国地层典》记失

文章列数了《中国地层典》5个方面的重要失误:不是中国地层名称全览性的工具书,急于采用处于争议中的术语,大量地层单位名称的出处因考证不到位而形成张冠李戴,采用的历史优先律不是国际共识,在编撰过程中建立新名称。文章用选出的泰山杂岩、滹沱系、秦岭片岩和仑山石灰岩4个名称为例说明《中国地层典》对其出处的考证不到位,进而论证《中国地层典》的诸多解释可信度低。文章严肃地指出“历史优先律”给中国地层学造成的不良后果:它破坏了地层命名法的标准性,颠倒了中国地层命名史,干扰了中国地层名称的管理。     

燕山中段南麓蓟县北部常州沟-杨庄一带地质构造基本特征

在燕山中段南麓的蓟县北部山区有着中国国家地质公园，中国北方中-新元古代正层型剖面标志碑就耸立在那里。对这一地区基本地质事实和地质体真实位态的研究，不仅关系着对华北地区晚前寒武纪标准剖面可靠性的评价，也关系着燕山运动命名地的基本地壳结构的合理解析和我国北方中生代以来构造一岩浆活动序列的正确建立。本文展示的基础地质调查成果可揭示：蓟县北部常州沟-杨庄一带的地质结构构造远不是我国大多数地学学者们对此描述的那样简单。调查区约200km。面积可代表燕山中段南麓的大面积中-新元古界分布区的基本地质结构构造特征。已识别出的18条断层和由其限制的21个以上构造岩片的现实位态表明，该地区地壳上部是由多个复杂地块堆叠构成的，主体构造形成于燕山晚期，在形成方式上以大规模多次不同方向运移的薄皮构造岩片叠覆为主要特征。     

Response of low‐angle dunes to variable flow

Current understanding of bedform dynamics is largely based on field and laboratory observations of bedforms in steady flow environments. There are relatively few investigations of bedforms in flows dominated by unsteadiness associated with rapidly changing flows or tides. As a consequence, the ability to predict bedform response to variable flow is rudimentary. Using high‐resolution multibeam bathymetric data, this study explores the dynamics of a dune field developed by tidally modulated, fluvially dominated flow in the Fraser River Estuary, British Columbia, Canada. The dunes were dominantly low lee angle features characteristic of large, deep river channels. Data were collected over a field ca 1·0 km long and 0·5 km wide through a complete diurnal tidal cycle during the rising limb of the hydrograph immediately prior to peak freshet, yielding the most comprehensive characterization of low‐angle dunes ever reported. The data show that bedform height and lee angle slope respond to variable flow by declining as the tide ebbs, then increasing as the tide rises and the flow velocities decrease. Bedform lengths do not appear to respond to the changes in velocity caused by the tides. Changes in the bedform height and lee angle have a counterclockwise hysteresis with mean flow velocity, indicating that changes in the bedform geometry lag changes in the flow. The data reveal that lee angle slope responds directly to suspended sediment concentration, supporting previous speculation that low‐angle dune morphology is maintained by erosion of the dune stoss and crest at high flow, and deposition of that material in the dune trough.     

Weakness and mechanical anisotropy of phyllosilicate-rich cataclasites developed after mylonites of a low-angle normal fault (Simplon Line,Western Alps)

The Simplon Fault Zone is a late-collisional low-angle normal fault (LANF) of the Western Alps. The hanging wall shows evidence of brittle deformation only, while the footwall is characterized by a c. 1 km-thick shear zone (the Simplon Fault Zone), which continuously evolved, during exhumation and cooling, from amphibolite facies conditions to brittle-cataclastic deformations. Due to progressive localization of the active section of the shear zone, the thermal-rheological evolution of the footwall resulted in a layered structure, with higher temperature mylonites preserved at the periphery of the shear zone, and cataclasites occurring at the core (indicated as the Simplon Line). In order to investigate the weakness of the Simplon Line, we studied the evolution of brittle/cataclastic fault rocks, from nucleation to the most mature ones. Cataclasites are superposed on greenschist facies mylonites, and their nucleation can be studied at the periphery of the brittle fault zone. This is characterized by fractures, micro-faults and foliated ultracataclasite seams that develop along the mylonitic SCC′ fabric, exploiting the weak phases mainly represented by muscovite and chlorite. Approaching the fault core, both the thickness and frequency of cataclasite horizons increase, and, as their thickness increases, they become less and less foliated. The fault core itself is represented by a thicker non-foliated cataclasite horizon. No Andersonian faults or fractures can be found in the footwall damage zone and core zone, whilst they are present in the hanging wall and in the footwall further from the fault. Applying a stress model based on slip tendency, we have been able to calculate that the friction coefficient of the Simplon Line cataclasites was <0.25, hence this fault zone is absolutely weak. In contrast with other fault zones, the weakening effect of fluids was of secondary importance, since they accessed the fault zone only after an interconnected fracture network developed exploiting the cataclasite network.     

Smoothing and re-roughening processes: The geometric evolution of a single fault zone

The geometry of a fault zone exerts a major control on earthquake rupture processes and source parameters. Observations previously compiled from multiple faults suggest that fault surface shape evolves with displacement, but the specific processes driving the evolution of fault geometry within a single fault zone are not well understood. Here, we characterize the deformation history and geometry of an extraordinarily well-exposed fault using maps of cross-sectional exposures constructed with the Structure from Motion photogrammetric method. The La Quinta Fault, located in southern California, experienced at least three phases of deformation. Multiple layers of ultracataclasite formed during the most recent phase. Crosscutting relations between the layers define the evolution of the structures and demonstrate that new layers formed successively during the deformation history. Wear processes such as grain plucking from one layer into a younger layer and truncation of asperities at layer edges indicate that the layers were slip zones and the contacts between them slip surfaces. Slip surfaces that were not reactivated or modified after they were abandoned exhibit self-affine geometry, preserving the fault roughness from different stages of faulting. Roughness varies little between surfaces, except the last slip zone to form in the fault, which is the smoothest. This layer contains a distinct mineral assemblage, indicating that the composition of the fault rock exerts a control on roughness. In contrast, the similar roughness of the older slip zones, which have comparable mineralogy but clearly crosscut one another, suggests that as the fault matured the roughness of the active slip surface stayed approximately constant. Wear processes affected these layers, so for roughness to stay constant the roughening and smoothing effects of fault slip must have been approximately balanced. These observations suggest fault surface evolution occurs by nucleation of new surfaces and wear by competing smoothing and re-roughening processes.     

Development of a new method for efficiently calculating of evaporation from the phreatic aquifer in variably saturated flow modeling

In this paper, we proposed a new method that has been developed based on the surface soil moisture content (SSMC) to more efficiently calculate the groundwater evaporation in variably saturated flow modeling. In this method, the empirical formula to calculate evaporation was modified and the value of the formula varies from zero to one as a closed interval. In addition, the simulation code for calculating the groundwater evaporation based on the SSMC method was incorporated into the EOS9 module of Tough2, a variably saturated flow modeling code. Finally, two numerical tests and a case simulation were conducted to verify the feasibility and accuracy of the SSMC method. Simulation results indicate that the SSMC method is capable of appropriately simulating the characteristics of water flow in vadose zone and the amount of evaporation with the variable water table. And such results are in coincidence with the value calculated by the logistic function method, and fit well with the measured data globally rather than locally.     

Formation of low permeability reservoirs and gas accumulation process in the Daniudi Gas Field,Northeast Ordos Basin,China

The Daniudi Gas Field is a typical large-scale coal-generated wet gas field located in the northeastern Ordos Basin that contains multiple Upper Paleozoic gas-bearing layers and considerable reserves of gas. Based on integrated analysis of reservoir petrology, carbonate cement C–O isotope, geochemistry of source rocks and HC gas and numerical basin modeling, a comprehensive study focusing on the formation of low permeability reservoirs and gas generation process uncovers a different gas accumulation scene in Daniudi Gas Field. The gas accumulation discovered was controlled by the reservoir permeability reduction and gas generation process, and can be divided into two distinct stages by the low permeability reservoir formation time: before the low permeability reservoir formation, the less matured gas was driven by buoyancy, migrated laterally towards NE and then accumulated in NE favorable traps during Late Triassic to early Early Cretaceous; after the low permeability reservoir formation, highly matured gas was driven by excessive pressure, migrated vertically and accumulated in-situ or near the gas-generating centers during early to late Early Cretaceous. The coupling relationship between reservoir diagenetic evolution and gas generation process controlled on gas accumulation of the Daniudi Gas Field. This study will aid in understanding the gas accumulation process and planning further E&D of the Upper Paleozoic super-imposed gas layers in the whole Ordos Basin and other similar super-imposed low permeability gas layer basins.     

New tectonic map of Northern-Central-Eastern Asia:Position and evolution of Mesozoic sedimentary basins

The beginning of the XXI century was marked a new rising of the international tectonic cartography as a result of analysis and synthesis of a huge volume of geological information obtained for the territory of Asia especially during the last 30 years. The previous tectonic maps for Asia were created in the 1960 s--1970 s of the last century. Since that time,the national geological surveys have compiled tectonic maps exclusively in the limits of their own state boundaries. The international cooperation of five countries since 2002( Russia,China,Mongolia,Kazakhstan and Republic of Korea) gave a unique possibility to join the data into a united cartographic form as Atlas of Geological Maps( since 2002-Atlas of Geological Maps of Central Asia and since 2007-Atlas of Geological Maps of Northern-Central-Eastern Asia). Both atlases include four maps: geological,tectonic,metallogenic,and energy resources. Tectonic Map of Northern-Central-Eastern Asia and Adjacent Areas at scale 1 ∶ 2 500 000 was the key map for further compilation of the metallogenic and energy resources( coal,oil and gas) maps. By this reason,special attention was given to showing the structure and composition of the Mesozoic sedimentary basins in Northern-Central- Eastern Asia as the most perspective structures for oil-and-gas and coal prospect.     

Petrochemistry of Granitoids Along the Loei Fold Belt,Northeastern Thailand

Petrochemical characteristics of Permo‐Triassic granitoids from five regions (i) Mung Loei, (ii) Phu Thap Fah – Phu Thep, (iii) Phetchabun, (iv) Nakon Sawan – Lobburi, and (v) Rayong – Chantaburi along the Loei Fold Belt (LFB), northeastern Thailand were studied. The LFB is a north–south trending 800 km fold belt that hosts several gold and base‐metal deposits. The granitoids consist of monzogranite, granodiorite, monzodiorite, tonalite, quartz‐syenite, and quartz‐rich granitoids. These are composed of quartz, plagioclase, and K‐feldspar with mafic minerals such as hornblende and biotite. Accessory minerals, such as titanite, zircon, magnetite, ilmenite, apatite, garnet, rutile, and allanite are also present. Magnetic susceptibilities in the SI unit of granitoids vary from 6.5 × 10⁻³ to 15.2 × 10⁻³ in Muang Loei, from 0.1 × 10⁻³ to 29.4 × 10⁻³ in Phu Thap Fah – Phu Thep, from 2.7 × 10⁻³ to 34.6 × 10⁻³ in Petchabun, from 2.4 × 10⁻³ to 14.1 × 10⁻³ in Nakon Sawan – Lobburi, and from 0.03 × 10⁻³ to 2.8 × 10⁻³ in Rayong – Chantaburi. Concentration of major elements suggests that these intermediate to felsic plutonic rocks have calc‐alkaline affinities. Concentration of REE of the granitoids normalized to chondrite displays moderately elevated light REE (LREE) and relatively flat heavy (HREE) patterns, with distinct depletion of Eu. Rb versus Y/Nb and Nb/Y tectonic discrimination diagrams illustrate that the granitoids from Muang Loei, Phu Thap Fah – Phu Thep, Phetchabun, Nakon Sawan – Lobburi, and Rayong – Chantaburi formed in continental volcanic‐arc setting. New age data from radiometric K‐Ar dating on K‐feldspar from granodiorite in Loei and Nakhon Sawan areas yielded 171 ± 3 and 221 ± 5 Ma, respectively. K‐Ar dating on hornblende separated from diorite in Lobburi yielded 219 ± 8 Ma. These ages suggest that magmatism of Muang Loei occurred in the Middle Jurassic, and Nakon Sawan – Lobburi occurred in Late Triassic. Both Nb versus Y and Rb versus (Y + Nb) diagrams and age data indicate that Nakon Sawan – Lobburi granitoids intruded in Late Triassic at Nong Bua, Nakon Sawan province and Khao Wong Phra Jun, Lobburi province in volcanic arc setting. Muang Loei granitoids at the Loei province formed later in Middle Jurassic also in volcanic arc setting. The negative δ³⁴S_CDT values of ore minerals from the skarn deposit suggest that the I‐type magma has been influenced by light biogenic sulfur from local country rocks. The Au‐Cu‐Fe‐Sb deposits correlate with the magnetite‐series granitoids in Phetchabun, Nakon Sawan – Lobburi and Rayong – Chantaburi areas. Metallogeny of the Au and Cu‐Au skarn deposits and the epithermal Au deposit is related to adakitic rocks of magnetite‐series granitoids from Phetchabun and Nakon Sawan areas. All mineralizations along the LFB are generated in the volcanic arc related to the subduction of Paleo‐Tethys. The total Al (^TAl) content of biotite of granitoids increases in the following order: granitoids associated with Fe and Au deposit < with Cu deposit < barren granitoids. X_Mg of biotite in granitoids in Muang Loei indicates the crystallization of biotite in magnetite‐series granitoids under high oxygen fugacity conditions. On the other hand, low X_Mg (<0.4) of biotite in magnetite‐series granitoids in Phu Thap Fah – Phu Thep and Rayong – Chantaburi indicates a reduced environment and low oxygen fugacity, associated with Au skarn deposit (Phu Thap Fah) and Sb‐Au deposit (Bo Thong), respectively. The magnetite‐series granitoids at Phu Thap Fah having low magnetic susceptibilities and low X_Mg of biotite were formed by reduction of initially oxidizing magnetite‐series granitic magma by interaction with reducing sedimentary country rocks as suggested by negative δ³⁴S_CDT values.     

余姚—丽水断裂带嵊州地区燕山期主要构造特征

余姚—丽水断裂带是浙东南地区活动时间长、延伸远、发育比较宽的一条NE—NNE展布的断裂构造带,在浙江嵊州地区上火山岩系磨石山群和下火山岩系永康群中构造形迹表现十分明显。余姚—丽水断裂带由一系列NE—NNE向控制区内白垩纪盆地形成与发展的正断层,以及NE—NNE走向、自北西向南东逆冲的叠瓦状断层和轴迹呈NE—NNE向的褶皱组成。通过对其构造活动特征及控制新老地层的时序关系研究,结合区域构造活动规律和时空演化关系等综合分析认为: 正断层形成时间较早,控制白垩纪盆地的形成和发展,与早白垩世岩石圈伸展减薄形成的拉张作用密切相关; 叠瓦状逆冲断层及斜歪褶皱、紧闭同斜褶皱等褶、断构造组合形成于晚白垩世之后,其动力学机制可能与古太平洋构造域向太平洋构造域的转换效应有关。研究成果为深入探讨浙东地区燕山期构造演化提供了新的素材和资料。