内蒙古霍各乞矿区含矿富石榴石岩晶体定量化结构分析及其意义

晶体粒度分布（CSD）是定量化分析火成岩和变质岩结构的重要手段。在变质岩中测量的CSD提供了有关变质过程中晶体成核和生长速率、生长时间的定量信息。文章选取内蒙古霍各乞二号矿床含矿富石榴石岩样品中石榴子石晶体为研究对象，在GIS软件和R语言的支持下，应用空间点模式分析、CSD分析、空间最邻近分析、空间多距离分析、Fry分析等综合方法，探讨了晶体空间数据和点空间数据表征的微结构变化特征，将CSD曲线分段变化记录的信息与地质演化历史联系起来。分段的CSD曲线记录了变质事件的叠加。不同形式的晶体粒度分布直接反映了区域变质岩与接触变质岩演化历史的差异。由于接触变质作用的高温阶段持续时间较短，因此产生的CSD曲线是线性的，不受退火的影响。而区域变质作用涉及长时间升温及其之后的冷却阶段，所以最初的线性CSD后来被退火改造为钟形曲线。含矿富石榴石岩样品的核密度和CSD分析结果显示了两个晶体群密度。分析认为一类晶体群可能与造山过程中的区域变质活动有关，另一类晶体群可能与大面积区域变质期后发生在特定位置的岩体侵入迅速升温的接触热变质事件有关。      

Verification of a simple gravity technique for separation of particle size fractions suitable for mineral magnetic analysis

Techniques for the separation of sediment samples into size fractions are reviewed and the use of repeated decantations to provide samples for mineral magnetic analysis is described. Results from a series of trials are presented and compared with other techniques.     

甘孜嘎拉金矿金的赋存状态初步研究

甘孜嘎拉金矿位于川西甘孜-理塘断裂带北段,该矿床具一定规模。笔者对该矿床自然金的产出状态,以及超显微金在黄铁矿、毒砂、辉锑矿主要载金矿物和各类矿石中的分布特征初步研究后,认为该矿床的金只有少量呈显微自然金形式赋存,大部分都是以超显微金的自然元素金混入各类载金体中,金的赋存状态指示该区金物源广,具良好的找金前景。     

A multivariate sedimentary environmental analysis of Great South Bay and South Oyster Bay, New York

A multivariate statistical strategy for classifying paleoenvironments is effective for studying modern sedimentary processes in western Great South Bay and South Oyster Bay, New York. The 13 whole phi weight percent variables were tested for redundancy with R-mode cluster analysis. The samples were partitioned statistically into five environmentally significant facies using Q-mode cluster analysis: (A)sandy gravel, (B)sandy silt, (C)silty sand, (D)slightly gravelly sand, and (E)fine sand. An ordination depicted gradational relationships among the samples and the facies. It was used to evaluate the environmental and textural parameter gradients within the sample space. Interpretations obtained in this manner and by examination of the grain-size curves suggest that these sediments were deposited by waves and currents on beaches and in wave zones (facies C and E),shoal areas (facies B),and tidal channels (facies A and D).Tidal currents, wave action, and eelgrass control the distribution of sediments within the two bays.     

Theory and applicability of a recrystallized grain size paleopiezometer

An approximate theoretical relation is derived which relates stress during steady state creep to both subgrain size and dynamically recrystallized grain size. The relation results from equating the dislocation strain energy in the grain boundary to that in the enclosed volume. Available data on metals and silicates are in excellent agreement with the theory. For paleopiezometry, the recrystallized grain size must be preserved by quenching, by cooling under stress, or by inhibition of grain growth by intimate mixture of two or more phases. In general, stress may be underestimated using rocks in which grain size has been reduced by dynamic recrystallization, especially if the grain size is very small. Stress may be overestimated using coarse grained rocks in which the grain size has increased toward the steady state value. Quantitative limits remain to be established. The theoretical relation can in principle be applied to any metal or mineral if only the effective isotropic elastic moduli and the Burgers vector are known. When used as a paleopiezometer, the technique indicates that high stresses on the order of 100 MPa are not infrequently associated with mantle diapirism and with large scale thrust faulting. Consideration of the Mt. Albert ultramafic body suggests that texturally inferred stresses from peridotite massifs and from ultramafic xenoliths in alkali olivine basalts might reflect either horizontal variations in stress across a rising diapir or else a vertical variation in stress as defined by the pyroxene geobarometer (Mercier et al. 1977). In either case the stresses are probably characteristic of local diapirism. Stresses characteristic of global upper mantle flow might be inferred from xenoliths originating from above kimberlite-producing diapirs.     

Dynamics of cracking and swelling clay soils: Displacement of skeletal grains,optimum depth of slickensides,and rate of intra-pedonic turbation

Grumusols (Vertisols), though having a uniformly high clay content with depth, commonly exhibit a coarsening upward in the sand fraction, either of skeletal grains or of nodules. The non-uniform way in which the wetting front advances in swelling clay soils, with preferred advance and swelling around the coarse grains, produces upward directional forces and uplifting of the grains, thus producing the observed textural differentiation in the coarse fraction. From observations of slickenside distribution in the profile, and using published data on the ratio of lateral to vertical stresses and swelling pressure distribution with depth, a concept of optimum depth for slickensides is developed. Generally at 150–200cm, below the depth of cracking, this depth depends in part on climatic conditions. Below the optimal depth increased overburden pressure and smaller moisture variations restrain the extent of swelling and deformation, above it drying produces cracks and obliterates large slickensides, though a strong bimasepic microfabric remains. The extent of intrapedonic turbation was estimated from measurements of the volume of cracks and of surface material falling into the cracks. It indicates a turnover time of several hundred to a few thousand of years. This agrees with the known increase of radiocarbon ages of organic matter (MRT) with depth which in Vertisols (Grumusols) is only slightly slower than in non-turbating Udolls (Chernozems) and Udalfs (Lessivés). The moderate rate of homogenization due to intrapedonic turbation does not prevent the development of a normal organic carbon profile and it is slower than the upswelling of coarse grains by upward directional forces. The development of shear planes and slickenside structures is a rapid process and not dependent on turbation.     

中国海域表层沉积物分布规律及沉积分异模式

中国海域拥有宽广的大陆架，同时还有陆坡和深海盆，有众多河流入海并输入巨量的陆源物质，沉积物记录了海陆变迁、环流变化、海平面升降、物质输送和气候变化等环境信息。沉积物的粒度特征可以反映沉积动力、物质来源和搬运距离等，可以通过沉积物粒度组成、参数及各种图解来研究沉积环境的变化。前人对中国海域表层沉积物的粒度分布特征展开了大量的研究，取得了丰富的研究成果，但这些研究多集中在某一海域或区域，缺乏对整个中国海域的表层沉积物类型的宏观系统认识。本文基于中国地质调查局“1：100万海洋区域地质调查项目”获取了中国海域4300个海底表层沉积物样品，通过沉积物粒度分析，结合前人已发表资料，对中国海域表层沉积物的沉积类型特征、物质来源和运移模式等开展了系统的研究。本文把浅海和半深海沉积物按照含砾石和不含砾石主要划分出5个和7个沉积物类型，深海沉积物主要划分了9个沉积类型，研究结果表明：中国海域表层沉积物沉积类型多样、来源复杂，主要受控于物质来源、水动力条件和地形地貌的变化，在东部海域总体呈现“大江大河-宽缓陆架-残留慢速沉积”的条带状沉积分异模式，而在南部海域呈现的是“短源性河流-多类型陆架-重力流快速沉积”的环带状沉积分异模式。本文的结果对研究中国海域沉积物的宏观分布规律提供了基础资料，对理解海洋沉积动力过程具有重要意义，同时沉积物粒度的特征对海底砂矿分布也具有指示意义。     

Dynamic behavior of single-layer latticed cylindrical shells subjected to seismic loading

The single-layer latticed cylindrical shell is one of the most widely adopted space-framed structures. In this paper, free vibration properties and dynamic response to horizontal and vertical seismic waves of single-layer latticed cylindrical shells are analyzed by the finite clement method using ANSYS software. In the numerical study, where hundreds of cases were analyzed, the parameters considered included rise-span ratio, length-span ratio, surface load and member section size. Moreover, to better define the actual behavior of single-layer latticed shells, the study is focused on the dynamic stress response to both axial forces and bending moments. Based on the numerical results, the effects of the parameters considered on the stresses are discussed and a modified seismic force coefficient method is suggested. In addition, some advice based on these rescarch results is presented to help in the future design of such structures.     

Deposits of depletive high-density turbidity currents: a flume analogue of bed geometry, structure and texture

Flume experiments were performed to study the flow properties and depositional characteristics of high‐density turbidity currents that were depletive and quasi‐steady to waning for periods of several tens of seconds. Such currents may serve as an analogue for rapidly expanding flows at the mouth of submarine channels. The turbidity currents carried up to 35 vol.% of fine‐grained natural sand, very fine sand‐sized glass beads or coarse silt‐sized glass beads. Data analysis focused on: (1) depositional processes related to flow expansion; (2) geometry of sediment bodies generated by the depletive flows; (3) vertical and horizontal sequences of sedimentary structures within the sediment bodies; and (4) spatial trends in grain‐size distribution within the deposits. The experimental turbidity currents formed distinct fan‐shaped sediment bodies within a wide basin. Most fans consisted of a proximal channel‐levee system connected in the downstream direction to a lobe. This basic geometry was independent of flow density, flow velocity, flow volume and sediment type, in spite of the fact that the turbidity currents of relatively high density were different from those of relatively low density in that they exhibited two‐layer flow, with a low‐density turbulent layer moving on top of a dense layer with visibly suppressed large‐scale turbulence. Yet, the geometry of individual morphological elements appeared to relate closely to initial flow conditions and grain size of suspended sediment. Notably, the fans changed from circular to elongate, and lobe and levee thickness increased with increasing grain size and flow velocity. Erosion was confined to the proximal part of the leveed channel. Erosive capacity increased with increasing flow velocity, but appeared to be constant for turbidity currents of different grain size and similar density. Structureless sediment filled the channel during the waning stages of the turbidity currents laden with fine sand. The adjacent levee sands were laminated. The massive character of the channel fills is attributed to rapid settling of suspension load and associated suppression of tractional transport. Sediment bypassing prevailed in fan channels composed of very fine sand and coarse silt, because channel floors remained fully exposed until the end of the experiments. Lobe deposits, formed by the fine sand‐laden, high‐density turbidity currents, contained massive sand in the central part grading to plane parallel‐laminated sand towards the fringes. The depletive flows produced a radial decrease in mean grain size in the lobe deposits of all fans. Vertical trends in grain size comprised inverse‐to‐normal grading in the levees and in the thickest part of the lobes, and normal grading in the channel and fringes of the fine sandy fans. The inverse grading is attributed to a process involving headward‐directed transport of relatively fine‐grained and low‐concentrated fluid at the level of the velocity maximum of the turbidity current. The normal grading is inferred to denote the waning stage of turbidity‐current transport.