大陆边缘增生造山作用

文章评述了增生造山作用的研究历史和进展,认为增生造山作用贯穿地球历史,是大陆增生的重要方式。用大陆边缘多岛弧盆系构造理解造山带的形成演化,提出巨型造山系的形成与长期发育的大洋岩石圈俯冲制约的两侧或一侧的多岛弧盆系密切相关。在多岛弧盆系演化过程中的弧 弧和弧 陆碰撞,弧前和弧后洋盆的消减冲杂岩的增生,洋底高原、洋岛/海山、外来地块(体)拼贴等一系列碰撞和增生造山作用形成大陆边缘增生造山系。大洋岩石圈最终消亡形成对接消减带,大洋岩石圈两侧的多岛弧盆系转化的造山系对接形成造山系的联合体。拼接完成后往往要继续发生大陆之间的陆 陆碰撞造山作用、陆内汇聚(伸展)作用,后者叠加在增生造山系上,使造山过程更加复杂。对接消减带是认识造山系形成演化的关键。大洋两侧多岛弧盆系经历的各种造山过程可以从广义上理解为一个增生造山过程。多岛弧盆系研究对于划分造山带细结构非常重要,是理解造山系物质组成、结构和构造的基础,并制约了造山后陆内构造演化。大陆碰撞前大洋两侧多岛弧盆系及陆缘系统更完整地记录了威尔逊旋回,记录的信息更加丰富。根据多岛弧盆系的思路对特提斯大洋演化提出新的模式,认为西藏冈底斯带自石炭纪以来受到特提斯大洋俯冲制约,三叠纪发生向洋增生造山作用,特提斯大洋于早白垩世末最终消亡。     

Structural analysis of a small area in the Wagonga beds at Narooma,N.S.W.

The small area surrounding Narooma provides an example of a departure from the ideal geometry of superposed fold systems. Three systems of folds are recognized, the second set being by far the best developed. Axial planes of these folds lack a preferred orientation so that the fold style is polyclinal and B‐axes are variable. Evidence of extension parallel to B is widespread. Some dynamic aspects of the second deformation are discussed.     

Influence of hydrogeology,microbiology and landscape history on the geochemistry of acid hypersaline waters,N.W. Victoria

There is now evidence that naturally occurring acid–water is more abundant than previously thought and that it has been important in the geologic past. Understanding the processes leading to the formation of such systems is required to appreciate the role of acid systems in geologic processes and to develop indicators for recognizing the geologic/environmental importance of these systems in the past. This paper characterizes the hydrogeology, hydrogeochemistry, microbial biogeochemistry and landscape attributes of acid–groundwater surface water systems in Australia with an emphasis on a well studied playa-lake system, Lake Tyrrell, Murray Valley. A model for the origin of these acid brines is presented and the importance of acid-brine producing systems is speculated upon. Data include porewater and groundwater geochemical measurements (collected during a 10 day field campaign) and results from geochemical modeling and graphics (e.g., Piper diagrams and x–y plots of seawater evaporation trajectories). Key characteristics of the system are (1) aquifer materials have low acid buffering capacities, (2) saline groundwater flowing onto playa surfaces is an oxic, H₂SO₄ solution, (3) authigenic minerals include combinations of jarosite [KFe₃(SO₄)₂(OH)₆], alunite [KAl₃(SO₄)₂(OH)₆] and Fe oxides that can form as evaporite minerals, (4) a source for solutes can be marine aerosols and (5) the formation of ironstones. Groundwater acidification by various processes including sulfide oxidation and ferrolysis, and at many different times, are the unique aspects for evolution of these acid brines and they can be considered another end member of the Eugster–Jones–Hardie model for the evolution of brines in closed basins. Acid–hypersaline groundwater and playa systems such as Lake Tyrrell may be an example of expected changes in the hydrogeochemistry of terrestrial water during late-stage continental denudation under arid conditions. Historically these systems may have been integral to the formation of opal, bauxite, some low temperature ore deposits, of authigenic K-feldspars, and continental redbeds. Natural acid saline systems, such as those in Australia, may also be representative of acid saline systems on Mars.     

Tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin, Cloverly and Lakota Formations (Lower Cretaceous) of Wyoming, U.S.A.

Continental sediments of the Cloverly and Lakota Formations (Lower Cretaceous) in Wyoming are subdivided into three depositional systems: perennial to intermittent alluvial, intermittent to ephemeral alluvial, and playa. Chert-bearing sandstones, conglomerates, carbonaceous mudrocks, blocky mudrocks, and skeletal limestones were deposited by perennial to intermittent alluvial systems. Carbonaceous mudrocks contain abundant wood fragments, cuticle and cortical debris, and other vascular plant remains representing deposition in oxbow lakes, abandoned channels, and on floodplains under humid to seasonal conditions. Intraformational conglomerates, sandstones, bioturbated and blocky mudrocks with caliche nodules, and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems. Bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo-slickensides. The presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi-arid conditions. Caliche nodules, pseudo-slickensides, and carbonate-rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi-arid climatic conditions. Laminated mudrocks, siltstones, vuggy carbonates, bedded to nodular evaporites, pebbly mudrocks, and diamictites were deposited in evaporative alkaline lakes or playas. Pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa, resulting from intense rain events within the basin.The areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the Early Cretaceous Cordilleran foreland basin in Wyoming. The lower part (A-interval) of the Cloverly and Lakota Formations is characterized by deposits of perennial to intermittent rivers that existed 300 to 1000 km east of the Sevier fold-and-thrust belt. Proximal to the Sevier fold-and-thrust belt, the A-interval of the Cloverly Formation and upper Ephraim Formation of the Gannett Group are typified by deposits of intermittent to ephemeral rivers and their associated floodplains. In the middle part (B-interval) of the Cloverly Formation, intermittent to ephemeral alluvial systems expand to 600 km into the basin. The upper part (C-interval) of the Cloverly Formation is characterized by playa deposits in the Bighorn and Wind River Basins and intermittent to ephemeral alluvial deposits along the front of the ancestral Sevier Mountains. Deposits of perennial to intermittent alluvial systems in the C-interval of the Cloverly and Lakota Formations are restricted to the Black Hills region, almost 900 km to the east of the Sevier Mountains. The change in the areal distribution of depositional systems through time within this continental foreland basin may be attributed to the development of a rain shadow associated with the uplift of the Sevier Mountains in the Early Cretaceous.     

Factors controlling net ecosystem metabolism in U.S. estuaries

High frequency dissolved oxygen data were analyzed to calculate primary production, respiration and net ecosystem metabolism (NEM) from 42 sites within 22 National Estuarine Research Reserves (NERR), 1995–2000. NERR sites are characterized by a variety of dominant plant communities including phytoplankton, salt marsh, seagrass, macroalgae, freshwater macrophyte, and mangrove, and are representative of the coastal bioregions of the United States. As expected from the wide diversity of sites, metabolic rates were temporally and spatially variable with the highest production and respiration occurring during the summer in Southeastern estuaries. Sites within different regions exhibited consistent seasonal trends in production, respiration, and NEM. Temperature was the most important environmental factor explaining within-site variation in metabolic rates; nutrient concentrations were the second most important factor. All but three of the 42 sites were heterotrophic (respiration was greater than production) on an annual basis. Habitat adjacent to the monitoring site, estuarine area, and salinity explained 58% of the variation in NEM. Open water sites or sites adjacent to mangroves or in marsh creeks were heterotrophic, while sites in or adjacent to submerged aquatic vegetation (eelgrass or macroalgal beds) were either autotrophic or near balance. Estuarine area was also a significant factor explaining variability in NEM; larger systems were closer to balance than smaller systems that trended toward heterotrophy. Freshwater sites were more heterotrophic than saline sites. Nutrient loading explained 68% of the variation in NEM among some of the sites. When these estimates were compared to the literature, metabolic rates from the NERR sites were much larger, often two to five times greater than rates from other estuarine and coastal systems. One explanation is that these small, generally shallow sites located near shore may have greater allochthonous organic inputs as well as significant benthic primary production than the large, deeper systems represented by the literature.     

http://www.sciencedirect.com/science/article/pii/S167498711100020X

Significant advances in regional groundwater flow modeling have been driven by the demand to predict regional impacts of human inferences on groundwater systems and associated environment.The wide availability of powerful computers,user friendly modeling systems and GIS stimulates an exponential growth of regional groundwater modeling.Large scale transient groundwater models have been built to analyze regional flow systems,to simulate water budget components changes,and to optimize groundwater developmen...     

http://www.sciencedirect.com/science/article/pii/S1674987114000413

Braid-delta depositional systems are widely developed in most continental basins in China. Research indicates that, for different types of braid delta, the facies sequence and association, which are cr...     

Did natural fission of 235U in the earth lead to formation of the supercontinent Columbia?

Steady decline in the percentage of 235U in terrestrial uranium made natural fission impossible after about 1.8 Ga.Fission before 1.8 Ga disturbed the lead isotope system at various places worldwide,su...     

The chemistry of geothermal waters in Iceland. II. Mineral equilibria and independent variables controlling water compositions

The major element chemistry of Icelandic geothermal waters is predictable provided two parameters are known. This follows from an attainment of, or a close approach to, an overall chemical equilibrium in the geothermal systems at temperatures as low as 50°C. It is considered that the geothermal system composition, temperature and kinetic factors determine which alteration minerals form. The system composition is not so much fixed by rock composition as by the rate of leaching of the various constituents from the fresh rock and the composition of inflowing water. The water chemistry is determined by the system composition and the external variables acting on the system. They include temperature and the mobility of chloride. Pressure, which theoretically should be regarded as an external variable, has insignificant effect on water compositions in the range (1–200 bars) occurring in the geothermal systems.     

Flow regime and bedforms in a ridge and runnel system,S.E. Spain

During landward migration, ridge and runnel systems are subjected to asymmetric oscillatory and/or unidirectional flow regimes, depending on the stage of development reached by these systems. In the early stages of evolution, when the ridge is situated in the upper shoreface, the whole system is subjected to asymmetric oscillatory flow. The runnel is under lower flow regime conditions and the ridge may be under upper or lower flow regime according to water depth and wave energy. Later, when the ridge has migrated to a position on the foreshore, the runnel is largely under a unidirectional lower flow regime while the ridge itself is under oscillatory upper flow regime. When the ridge welds to berm, it is largely emergent and exposed to high-tide swash action under upper flow regime conditions. The runnel is eventually filled with sand and transformed into a low-lying area. All these types grade laterally into each other. One or more ridge and runnel systems can occur at the same time. Wave energy, tide level and position of the ridge control the variations in the characteristics of the ridge and also the position of the zones of bedforms found at the upper shoreface.     

构造转换带储集体发育的主控因素——以准噶尔盆地腹部侏罗系为例

本文以准噶尔盆地腹部侏罗系储集砂体分布特征为例,探讨构造变换带优质储层的形成机制与变形特征,开展构造转换带的构造-沉积-成岩作用等对物源、砂体、岩石物理等的控制作用的研究。盆地构造转换带控制主要物源与水系,进而控制沉积体系的发育特征;构造转换带与坡折带共同控制沉积相带展布;构造转换带、坡折及沉积层序格架联合控制砂体时空展布及其储层质量:在大的构造转换带、高坡降比的坡折等条件下,在低位域沉积期发育冲积扇、辫状河和曲流河沉积等,形成大规模的储集体,在高位域沉积期发育较大规模三角洲沉积等。对构造转换带的综合研究,可深化对坳陷盆地沉积体系发育规律认识,进而提高对油气储集体的预测精度,对陆相湖盆沉积学及其油气勘探开发具有重要指导和参考价值。     

http://www.sciencedirect.com/science/article/pii/S1674987111000235

In this paper we present a review of mineral systems in northern Xinjiang,NW China,focussing on the Tianshan,West and East Junggar and Altay orogenic belts,all of which are part of the greater Central Asian Orogenic Belt(CAOB).The CAOB is a complex collage of ancient microcontinents,island arcs,oceanic plateaux and oceanic plates,which were amalgamated and accreted in Early Palaeozoic to Early Permian times.The establishment of the CAOB collage was followed by strike-slip movements and affected by intrap...     

http://www.sciencedirect.com/science/article/pii/S1674987111001083

Stable carbon isotope geochemistry provides important information for the recognition of fundamental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elaboration of models for the global carbon cycle.Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon（organic matter,mantle,or carbonates） and help to constrain the fluid history and the mechanisms involved in graphite deposition.Graphite precipitation in fluid-deposited occurrences results from CO₂- and/or CH₄-bearing aqueous fluids.Fluid flow can be considered as both a closed（without replenishment of the fluid） or an open system（with renewal of the fluid by successive fluid batches）.In closed systems,carbon isotope systematics in graphite is mainly governed by Rayleigh precipitation and/or by changes in temperature affecting the fractionation factor between fluid and graphite.Such processes result in zoned graphite crystals or in successive graphite generations showing,in both cases, isotopic variation towards progressive ^l3C or ¹²C enrichment（depending upon the dominant carbon phase in the fluid.CO₂ or CH₄,respectively）.In open systems,in which carbon is episodically introduced along the fracture systems,the carbon systematics is more complex and individual graphite crystals may display oscillatory zoning because of Rayleigh precipitation or heterogeneous variations of 5’ C values when mixing of fluids or changes in the composition of the fluids are the mechanisms responsible for graphite precipitation.     

盆山结构与油气分布——以四川盆地为例

根据四川盆地与周缘造山带地貌学、深浅部结构构造及动力学机制等, 其盆山结构可分为板缘(龙门山、米仓山和大巴山)突变型和板内(齐岳山、大娄山和大凉山)渐变型两类。板缘突变型盆山结构具有显著深部结构差异性,浅部构造具典型冲断带(山)和前陆盆地(盆)二元结构,其盆山耦合关系主要受控于深部结构的差异性和造山带的形成演化过程,现今山盆地貌反差大,地形坡度陡,盆山边界明晰。板内渐变型盆山结构, 则深部结构特征相似,浅部构造具挤压-坳陷结构、不发育大规模冲断推覆,现今山盆地貌反差小、盆山边界不清, 盆山为渐变过渡关系,其盆山耦合关系主要受控于邻区(盆外)的构造变形和盆内沉积盖层中多层次滑脱作用。不同盆山结构主要通过对现今四川盆地保存条件的影响而控制现今油气分布。四川盆地现今(残存)大中型油气藏和天然气探明储量的大部分主要分布于突变型盆山结构区,尤其是秦岭构造变形控制域。     

Mineral systems,their types,and distribution in nature. I. Khibiny,Lovozero, and the Mont Saint-Hilaire

In accordance with the set of species-defining chemical elements in minerals, n-component systems (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) for all mineral species (4952) known to 2014 inclusive were distinguished. Seventy chemical elements have been established to be species-defining, which are distributed by mineral systems as follows: 1 (29), 2 (62), 3 (68), 4 (61), 5 (61), 6 (55), 7 (49), 8 (38), 9 (28), and 10 (19). The number of mineral species in which certain chemical elements are species-defining has been specified. Oxygen (4041), hydrogen (2755), silicon (1448), calcium (1139), sulfur (1025), aluminum (960), iron (917), sodium (914), copper (616), phosphorous (580), arsenic (575), and magnesium (550) are the leading elements in minerals in the Earth’s crust. It has been found that the most species-defining elements are normally distributed by mineral systems. The distributions of mineral species in various systems from the Khibiny and Lovozero, Kola Peninsula, Russia; and Mont Saint-Hilaire, Quebec, Canada peralkaline plutons were compared and the characters of species-defining element distribution in these localities were compared. Si, Na, K, C, F, Ti, Ce, Zr, Nb, Sr, and Th are “excess” species-defining elements in minerals from the plutons compared to the total number of mineral species, whereas S, Cu, Pb, Cl, B, Te, Ag, Ni, and Be are “scarce” elements.     

地球化学开放系统的质量平衡:1.理论

从质量守恒原理出发推导出开放系统两个新的质量平衡方程：Ｃ＾ｏｉ－Ｃ＾Ａｉ－△Ｃｉ,（Ｃ＾Ｏｉ－Ｃ＾Ａｉ）／Ｃ＾Ｏｉ＝μ（Ｃ＾Ａｉ／Ｃ＾Ｏｉ）－μｉ。该方程不公在图示和计算方面均优于Ｇｒａｎｔ方程,而且还同时将Ｂｒｉｍｈａｌｌ和Ｄｉｅｔｒｉｃｈ质量平衡方程作为一个特例而包容它。     

Organic geochemistry and mineralogy. I. Characterisation of organic matter associated with metal deposits

As geochemical appraisals of mineral regions of commercial prospectivity evolve, the organic matter associated with metal rich ores has attracted greater attention. Petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids. There have been many isolated reports of certain organic compositional or morphological (e.g. pyrobitumen) features showing an apparent relationships with hydrothermal fluids or minerals, raising expectations that organic based parameters might be useful to mineral exploration. However, the understanding of organic–inorganic relationships in Earth systems is far from complete. For example, the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined. Organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks. Here we review the types of aliphatic hydrocarbons, aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral-rich regions. Such molecular data can be particularly diagnostic of biochemical sources and the palaeo-environments at the time mineral associated organic matter was deposited. Sub-surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation. Organic geochemistry data can also occasionally provide information about the nature (e.g., origin, composition, temperatures) and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models. The well preserved organic matter associated with the economic “Here's Your Chance” Pb–Zn–Ag Mine (Paleoproterozoic Barney Creek Formation, McArthur Basin, Australia) and the transition metal-rich Early Permian Kupferschiefer Formation (Germany–Poland) have attracted significant attention. A more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes. Most organic geochemical studies of highly mineralised regions, however, have not adequately addressed the significance of organic matter to mineralisation. A slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation, transport and deposition of ore metals. The characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic–inorganic fluids or other affiliated organics in ore systems.     

Occurrence and origin of marialitic scapolite in the Humboldt lopolith,N.W. Nevada

The occurrence and origin of marialitic scapolite in the Humboldt lopolith was investigated in the field and in the laboratory using petrographic and experimental techniques. Scapolite occurs in three modes: as a pervasive replacement of plagioclase and other minerals in gabbro, diorite and extrusive rocks; as a poikiloblastic mineral in scapolitite dikes; and as a fracture-filling mineral with analcime, albite and sphene in scapolite veins. Additional secondary minerals associated with scapolite include epidote, prehnite, hornblende and diopside-salite clinopyroxene. Relations with these minerals suggest that most marialitic scapolite grew at temperatures around 400° C. Scapolite composition varies from EqAn₁₂ to EqAn₃₇, containing from 72 to 96 atomic% Cl in the R position. Experiments on systems of similar compositions indicate that NaCl-H₂O fluid having more than 40 mol% NaCl is needed to stabilize the scapolite.Variation in scapolite compositions is due to thermal and fluid compositional gradients normal to conduits of hydrothermal fluids, and occurs on a scale up to 100 m. The likely source of Na and Cl is pre-existing evaporites or evaporitic brine derived from the wallrocks. Salinity could have been increased to a level sufficient to stabilize scapolite by hydration of an originally dry magma, possibly aided by hydrothermal boiling. Results may be applied to hydrothermal alteration in areas of rifting or back-arc spreading, and in mid-ocean ridge hydrothermal systems.     

A. Programmable device for simulation of tidal flux

An apparatus is described which permits precise, versatile control of simulated tidal flux in laboratory microcosms. A key component of the system, a programmable electronic control unit, can closely imitate any natural tidal function and is readily adaptable to other experimental applications that utilize timed switching capability. The programmable control unit is also cheaper and easier to operate than computer-based systems.