单细胞海藻有机质热演化特征与成烃性能

以单细胞海藻为材料进行热模拟生烃试验。对其不同温度级别下的元素分析。红外光谱和有机差热等测试分析，结果表明，单细胞海藻有机质演化呈现出阶段性特点，从常温到300℃为未成熟阶段。产烃性能好；300-400℃为主要产烃期，有机质已达成熟阶段；400-500℃时海藻有机质产烃性能明显减弱，为过成熟阶段，热模拟试验结果表明，单细胞海藻是良好的生烃原始母质，并清晰地显示出了单细胞海藻有机质的热演化特征和生烃历程。     

中国内蒙古白云鄂博Fe-Nb-REE矿床地质特征与陨石撞击成因

中国内蒙古白云鄂博Ｆｅ－Ｎｂ－ＲＥＥ矿床由于其独特的矿床地质与矿物地球化学特征而明显有别于世界上其它绝大多数的Ｆｅ、Ｎｂ、ＲＥＥ矿床。本文提出该矿床是约１５００Ｍａ前一块富含ＲＥＥ、Ｎｂ的铁陨石撞击在华北地台北缘碳酸盐沉积陆架上形成的。现在矿床矿体中心的块状铁矿石更多地代表了陨石的成分,矿体外侧富含ＲＥＥ、Ｎｂ的环状白云岩是陨石撞击浅海碳酸盐沉积陆架释放的巨大能量使海水（含Ｍｇ）迅速受热溶解陨石中的ＲＥＥ、Ｎｂ等形成的含金属热液蚀变沉积成因方解石质碳酸盐沉积物的结果。块状铁矿石和环状白云岩之间矿物成分异常复杂、结晶颗粒十分细小的条带状、侵染状Ｆｅ－Ｎｂ－ＲＥＥ矿石组成的矿体则是撞击瞬间导致的由陨石（Ｆｅ、Ｎｂ、ＲＥＥ）、海水（Ｍｇ、Ｎａ、Ｋ等）和碳酸盐（含少量硅质夹层）（Ｃａ、Ｓｉ、Ａｌ等）组成的超高温、多组分、富水体系在快速冷却条件下反应生成的产物。撞击释放的巨大热能,在撞击体（陨石）下部相对不易释放,导致部分碳酸盐沉积物在富含ＲＥＥ、Ｎｂ、Ｍｇ等的热液参与下融熔,然后侵入到周围岩石裂隙形成矿区内众多的富含ＲＥＥ、Ｎｂ的白云岩脉。撞击的瞬间导致大量岩石、矿物碎屑、海水、蒸汽弥漫天空,同时引发巨大的海啸,然     

新仙女木事件的发生及其全球性意义

综合国内外学者对短时间尺度气候事件的研究成果 ,对新仙女木事件 ( YD)的全球性分布及其界定方法和成因机制进行探讨。揭示了新仙女木期的气候特征和多种不同的气候替代指标 ,表明在太阳辐射 -大气 -冰盖 -陆地 -生物相互作用、多层次反馈的全球气候系统中存在着非线性气候变化 ,且在时间上、地域上存在着明显的差别 (不同步性 )。进一步阐明了 YD事件是全球性气候突变事件 ,是全球气候变暖、海平面上升过程中一次短暂的滞缓或回返 ,支持了 Fairbanks的气候 -海平面变化理论。冰期 -全新世过渡期气候变暖的驱动力是地球轨道参数的变化 ,YD事件作为非轨道事件 ,其驱动力可能归因于全球 CO2 浓度的变化 ,但 CO2 变化的因果关系至今尚无定论。     

Geospatially based distributed rainfall‐runoff modelling for simulation of internal and outlet responses in a semi‐forested lower Himalayan watershed

This study presents a Geographic Information System (GIS)‐based distributed rainfall‐runoff model for simulating surface flows in small to large watersheds during isolated storm events. The model takes into account the amount of interception storage to be filled using a modified Merriam ( 1960 ) approach before estimating infiltration by the Smith and Parlange ( 1978 ) method. The mechanics of overland and channel flow are modelled by the kinematic wave approximation of the Saint Venant equations which are then numerically solved by the weighted four‐point implicit finite difference method. In this modelling the watershed was discretized into overland planes and channels using the algorithms proposed by Garbrecht and Martz ( 1999 ). The model code was first validated by comparing the model output with an analytical solution for a hypothetical plane. Then the model was tested in a medium‐sized semi‐forested watershed of Pathri Rao located in the Shivalik ranges of the Garhwal Himalayas, India. Initially, a local sensitivity analysis was performed to identify the parameters to which the model outputs like runoff volume, peak flow and time to peak flow are sensitive. Before going for model validation, calibration was performed using the Ordered‐Physics‐based Parameter Adjustment (OPPA) method. The proposed Physically Based Distributed (PBD) model was then evaluated both at the watershed outlet as well as at the internal gauging station, making this study a first of its kind in Indian watersheds. The results of performance evaluation indicate that the model has simulated the runoff hydrographs reasonably well within the watershed as well as at the watershed outlet with the same set of calibrated parameters. The model also simulates, realistically, the temporal variation of the spatial distribution of runoff over the watershed and the same has been illustrated graphically. Copyright © 2011 John Wiley & Sons, Ltd.     

Diachronous Palaeoproterozoic deformation and metamorphism in the Committee Bay belt,Rae Province,Nunavut: insights from 40Ar–39Ar cooling ages and thermal modelling

Regional‐scale ⁴⁰Ar–³⁹Ar data presented in this paper reveal significant across‐strike and along‐strike age differences in the Committee Bay belt (CBb), Rae Province, Nunavut, Canada, that complement variations in observed monazite ages. ⁴⁰Ar–³⁹Ar hornblende ages are c. 1795, 1775, and 1750 Ma in the western, eastern and central parts of the Prince Albert Group (PAG) domain respectively. The migmatite domain and Walker Lake intrusive complex are characterized by c. 1750–1730 ⁴⁰Ar–³⁹Ar hornblende ages without significant along‐strike variation. The ⁴⁰Ar–³⁹Ar data provide important constraints on the cooling history and on thermal modelling that elucidates the controls on diachroneity and metamorphic patterns within the belt. In the western CBb, prograde monazite growth occurred 26 ± 10 Myr earlier in the migmatite domain (1864 ± 9 Ma; peak P–T = 5 kbar?700 °C) than in the PAG domain (1838 ± 5 Ma; peak P–T = 5 kbar?580 °C). Calculations indicate that this earlier monazite growth results from tectonic thickening of higher heat productivity Archean lithologies in the migmatite domain, which undergoes more rapid prograde heating than the less radiogenetic and lower grade rocks of the PAG domain. Granite generation via biotite dehydration melting at 800 °C and 20 km depth is predicted to occur c. 1835 Ma, in agreement with geochronological constraints. The tectonic burial of crustal domains with contrasting radiogenic properties also explains the general congruence of lower to upper amphibolite facies metamorphic zones generated during the two main orogenic cycles (i.e. M₂–D₁ and M₃–D₂). The modelled timing of prograde monazite growth in the migmatite domain suggests that D₂ tectonic thickening began at 1872 ± 9 Ma, some 8 ± 3 Myr before monzazite growth, coeval with the inferred time of collision of the Meta Incognita terrane with the southern Rae Province. Along‐strike diachroneity, reflected in 25 Myr younger monazite and ⁴⁰Ar–³⁹Ar hornblende ages in the eastern relative to the western PAG domain, cannot be accounted for by heat productivity contrasts along the belt. Instead the younger deformation and metamorphism in the eastern CBb was driven by its proximity to the eastern promontory of the Superior Province which collided with the Rae Province at c. 1820 Ma. The ⁴⁰Ar–³⁹Ar data presented here support the interpretation that the youngest monazite in the CBb crystallized at c. 1790 Ma in the central CBb when this part of the belt was downfolded into a gentle synformal structure while the western part of the belt cooled through ⁴⁰Ar–³⁹Ar hornblende closure. The results of this study illustrate the important influence of contrasting rock properties on the thermal evolution of orogenic belts and on the temporal record of this evolution.     

Parameterization and multi‐criteria calibration of a distributed storm flow model applied to a Mediterranean agricultural catchment

The principal challenge in the parameterization of storm flow models for agricultural catchments with an artificial drainage network and fields with different degrees of tillage lies in the parsimonious definition of distributed model parameters in a way that reduces the number of calibration parameters to a justifiable minimum. This paper presents a comprehensive case study for the parameter estimation of a distributed storm flow model applied to an agricultural catchment (0.91 km²) in the Mediterranean region. Model parameterization was combined with procedures for multi‐criteria, multi‐storm calibration, where we automatically calibrated three parameters related to flow velocity and infiltration, and compared single and multi‐storm criteria that are based on discharge volume, peak flow, and the Nash–Sutcliffe coefficient. Multi‐storm calibration yielded a set of parameter values for the simulation batch with best multi‐storm overall performance, which are close to the median values in the pre‐calibration of individual storms. Our results suggest that flow velocities and proportionality of the channel infiltration rate do not vary significantly over the course of 11 years. Copyright © 2012 John Wiley & Sons, Ltd.     

Transitions to chaotic thermal convection in a rapidly rotating spherical fluid shell

Abstract

Numerical simulations of thermal convection in a rapidly rotating spherical fluid shell heated from below and within have been carried out with a nonlinear, three-dimensional, time-dependent pseudospectral code. The investigated phenomena include the sequence of transitions to chaos and the differential mean zonal rotation. At the fixed Taylor number T _a =10⁶ and Prandtl number Pr=1 and with increasing Rayleigh number R, convection undergoes a series of bifurcations from onset of steadily propagating motions SP at R=R _c = 13050, to a periodic state P, and thence to a quasi-periodic state QP and a non-periodic or chaotic state NP. Examples of SP, P, QP, and NP solutions are obtained at R = 1.3R _c , R = 1.7 R _c , R = 2R _c , and R = 5 R _c , respectively. In the SP state, convection rolls propagate at a constant longitudinal phase velocity that is slower than that obtained from the linear calculation at the onset of instability. The P state, characterized by a single frequency and its harmonics, has a two-layer cellular structure in radius. Convection rolls near the upper and lower surfaces of the spherical shell both propagate in a prograde sense with respect to the rotation of the reference frame. The outer convection rolls propagate faster than those near the inner shell. The physical mechanism responsible for the time-periodic oscillations is the differential shear of the convection cells due to the mean zonal flow. Meridional transport of zonal momentum by the convection cells in turn supports the mean zonal differential rotation. In the QP state, the longitudinal wave number m of the convection pattern oscillates among m = 3,4,5, and 6; the convection pattern near the outer shell has larger m than that near the inner shell. Radial motions are very weak in the polar regions. The convection pattern also shifts in m for the NP state at R = 5R _c , whose power spectrum is characterized by broadened peaks and broadband background noise. The convection pattern near the outer shell propagates prograde, while the pattern near the inner shell propagates retrograde with respect to the basic rotation. Convection cells exist in polar regions. There is a large variation in the vigor of individual convection cells. An example of a more vigorously convecting chaotic state is obtained at R = 50R _c . At this Rayleigh number some of the convection rolls have axes perpendicular to the axis of the basic rotation, indicating a partial relaxation of the rotational constraint. There are strong convective motions in the polar regions. The longitudinally averaged mean zonal flow has an equatorial superrotation and a high latitude subrotation for all cases except R = 50R _c , at this highest Rayleigh number, the mean zonal flow pattern is completely reversed, opposite to the solar differential rotation pattern.     

A thermo‐mechanical model for the catastrophic collapse of large landslides

In this work, a new thermo‐mechanical model is developed, applicable to large‐scale, deep‐seated landslides consisting of a coherent mass sliding on a thin clayey layer. The considered time window is that of catastrophic acceleration, starting at incipient failure and ending when the acquired displacement and velocity are such that the sliding material begins to break up into pieces. The model accounts for temperature rise in the slip zone due to the heat produced by friction, leading to water expansion, thermoplastic collapse of the soil skeleton, and subsequent increase of pore water pressure. The model incorporates the processes of heat production and diffusion, pore pressure generation and diffusion, and an advanced constitutive law for the thermo‐mechanical behavior of soil. An analysis of the Vajont landslide is presented as an example. A sensitivity analysis shows that friction softening is the mechanism most affecting the timescale of the final collapse of a slide, but also that the mechanism of thermal pressurization alone can cause a comparably catastrophic dynamic evolution. It is also shown that, all other factors being equal, thermo‐mechanical collapse will cause thicker slides to accelerate faster than shallow ones. Copyright © 2010 John Wiley & Sons, Ltd.