Numerical Modelling of Ore-forming Dynamics of Fractal Dispersive Fluid Systems

Based on an analysis of the fractal structures and mass transport mechanism of typical shear-fluid-ore formation system, the fractal dispersion theory of the fluid system was used in the dynamic study of the ore formation system. The model of point-source diffusive illuviation of the shear-fluid-ore formation system was constructed, and the numerical simulation of dynamics of the ore formation system was finished. The result shows that: (1) The metallogenic system have nested fractal structure. Different fractal dimension values in different systems show unbalance and inhomogeneity of ore-forming processes in the geohistory. It is an important parameter to symbolize the process of remobilization and accumulation of ore-forming materials. Also it can indicate the dynamics of the metallogenic system quantitatively to some extent. (2) In essence, the fractal dispersive ore-forming dynamics is a combination of multi-processes dominated by fluid dynamics and supplemented by molecule dispersion in fluids and fluid-rock interaction. It changes components and physico-chemical properties of primary rocks and fluids, favouring deposition and mineralization of ore-forming materials. (3) Gold ore-forming processes in different types of shear zones are quite different. (1) In a metallogenic system with inhomogeneous volumetric change and inhomogeneous shear, mineralization occurs in structural barriers in the centre of a shear zone and in geochemical barriers in the shear zone near its boundaries. But there is little possibility of mineralization out of the shear zone. (2) As to a metallogenic system with inhomogeneous volumetric change and simple shear, mineralization may occur only in structural barriers near the centre of the shear zone. (3) In a metallogenic system with homogeneous volumetric change and inhomogeneous shear, mineralization may occur in geochemical barriers both within and out of the shear zone.

Enduring effect of permeability texture for enhancing accuracy and reducing uncertainty of reservoir fluid flow through porous media

Modeling reservoir permeability is one of the crucial tasks in reservoir simulation studies.Traditionally,it is done by kriging-based methods.More rigorous modeling of the permeability results in more reliable outputs of the reservoir models.Recently,a new category of geostatistical methods has been used for this purpose,namely multiple point statistics(MPS).By this new category of permeability modeling methods,one is able to predict the heterogeneity of the reservoir permeability as a continuous variable.These methods consider the direction of property variation in addition to the distances of known locations of the property.In this study,the reservoir performance of a modified version of the SPE 10 solution project as a pioneer case is used for investigating the efficiency of these methods and paralleling them with the kriging-based one.In this way,the permeability texture concept is introduced by applying some MPS methods.This study is accomplished in the conditions of real reservoir dimensions and velocities for the whole reservoir life.A continuous training image is used as the input of calculation for the permeability modeling.The results show that the detailed permeability of the reservoir as a continuous variable makes the reservoir simulation show the same fluid front movement and flooding behavior of the reservoir similar to the reference case with the same permeability heterogeneity.Some MPS methods enable the reservoir simulation to reproduce the fluid flow complexities such as bypassing and oil trapping during water flooding similar to the reference case.Accordingly,total oil production is predicted with higher accuracy and lower uncertainty.All studied cases are identical except for the permeability texture.Even histograms and variograms of permeabilities for the studied reservoir are quite similar,but the performance of the reservoir shows that kriging-based method results have slightly less accuracy than some MPS methods.Meanwhile,it results in lower uncertainty in outputs for this water flooding case performance.

Genesis, metallogenic model, and prospecting prediction of the Nibao gold deposit in the Guizhou Province, China

Southwestern Guizhou province is one of China’s most important distribution areas of Carlin-type gold deposits. The Nibao deposit is a typical gold deposit in southwestern Guizhou. To elucidate the genesis of the Nibao gold deposit, establish a metallogenic model, and guide prospecting prediction, we systematically collected previously reported geological, geochemical, and dating data and discussed the genesis of the Nibao gold deposit,based on which we proposed the metallogenic model.Earlier works show that the Nibao anticline, F1 fault, and its hanging wall dragged anticline(Erlongqiangbao anticline) were formed before or simultaneously with gold mineralization, while F2, F3, and F4 faults postdate gold mineralization. Regional geophysical data showed extensive low resistivity anomaly areas near the SBT(the product of tectonic slippage and hydrothermal alteration)between the P2/P3 and the strata of the Longtan Formation in the SSE direction of Nibao anticline in the lower plate of F1 and hanging wall dragged anticline(Erlongqiangbao anticline), and the anomaly areas are distributed within the influence range of anticlines. Simultaneously, soil and structural geochemistry show that F1, Nibao anticline,Erlongqiangbao anticline, and their transition areas all show good metallogenic elements(Au, As, and S) assemblage anomalies, with good metallogenic space and prospecting possibilities. There are five main hypotheses about the source of ore-forming fluids and Au in the Nibao gold deposit:(1) related to the Emeishan mantle plume activity;(2) source from the Emeishan basalt;(3) metamorphic fluid mineralization;(4) basin fluid mineralization;(5) related to deep concealed magmatic rocks;of these, the mainstream understanding is the fifth speculation. It is acknowledged that the ore-forming fluids are hydrothermal fluids with medium–low temperature, high pressure, medium–low salinity, low density, low oxygen fugacity, weak acidity, weak reduction, and rich in CO_(2)and CH_(4). The fluid pressure is 2–96.54 MPa, corresponding to depths of 0.23–3.64 km. The dating results show that the metallogenic age is ~141 Ma, the extensional tectonic environment related to the westward subduction of the Pacific Plate. Based on the above explanation, the genetic model related to deep concealed magmatic rocks of the Nibao gold deposit is established, and favorable prospecting areas are outlined;this is of great significance for regional mineral exploration and studying the genesis of gold deposits.

滇西北红山晚白垩世花岗斑岩型Cu-Mo成矿系统及其大地构造学意义

红山铜多金属矿床位于滇西北中甸红山一带，其一直被认为是印支期夕卡岩型矿床。新的研究结果表明红山矿区存在两个成矿系统：①与印支期石英二长斑岩有关的夕卡岩型铜多金属成矿系统，其典型矿床是与石榴子石夕卡岩伴生的含铜磁铁矿体与磁黄铁矿体；②与花岗斑岩有关的斑岩型Cu—Mo～Pb—Zn成矿系统，其包括地表喷溢沉积成因的含铁钙硅质岩、可能为流体通道相的Cu—Mo多金属石英网脉与大脉、充填于岩溶洞穴中的层状Pb—Zn矿体、花岗斑岩内部的浸染状Cu—Mo矿化、及岩体外接触带夕卡岩型多金属矿床。含矿石英脉6个辉钼矿样品Re—Os模式年龄介于75．46～78．46Ma之间，等时线年龄为77Ma，红山矿区花岗斑岩型Cu～Mo矿床形成时代为晚白垩世。红山矿区晚白垩世花岗斑岩及其伴生斑岩型Cu—Mo矿床和大规模流体活动是滇西地区晚白垩世区域构造一流体一成矿体系的一部分，其形成与印度亚洲大陆碰撞有关，据此可推断印度～亚洲大陆的碰撞作用及其伴生的大规模成矿作用在77Ma就已开始。红山矿区晚白垩世斑岩型Cu—Mo矿床成矿系统的厘定对于斑岩型矿床成矿流体结构模型和区域成矿与构造学的研究具重要的启示意义。

攀枝花铁矿朱家包包矿段层状铁矿体的成因:来自矿物结构定量化分析的证据

岩浆型铁矿床是中国最重要的铁矿类型之一,攀枝花式铁矿赋存于攀枝花大型层状侵入体中,同时是峨眉山地幔柱系统的组成部分。然而此类矿床的成因问题仍未得到有效的解决。文中以攀枝花铁矿朱家包包矿段中部岩相带(MZ)为例,采用定量化结构分析的方法,结合地质学和岩相学观察结果,试图从攀枝花岩体中部岩相带辉长岩中单斜辉石的结构角度解释攀枝花式铁矿层状矿体的成因。岩相学观察可见部分样品中单斜辉石和斜长石具有明显的溶蚀结构以及角闪石、蛇纹石的增生边,被溶蚀的部分由铁钛氧化物填充,而铁钛氧化物之间发育共结结构。晶体粒度分布(CSD)显示,被溶蚀的单斜辉石较未溶蚀样品具有更陡的CSD曲线斜率,CSD曲线小颗粒处弯曲程度更大,以及更高的铁矿含量,说明溶蚀作用导致了CSD曲线变得更陡,产生了类似于粗化作用的CSD曲线。晶体空间分布(SDP)显示中部岩相带岩体上部有分选的趋势,而岩体下部则表现出挤压的趋势,说明了岩体上部保留了岩浆结晶过程中的矿物颗粒分选的趋势,而下部由于普遍的溶蚀导致了矿物粒间空隙增大,难以支撑上部的荷载,表现出挤压趋势。造岩矿物溶蚀、富水的角闪石、蛇纹石生长边以及填隙的铁钛氧化物说明有流体存在。在攀枝花岩体中段结晶晚期,富铁流体加入半固结的岩体使得造岩矿物溶蚀,而后填充于空隙,流体逃逸后铁矿物富集沉淀成矿。岩体下部具普遍的溶蚀作用,受荷载富铁流体被挤压逃逸,形成了块状的贫铁岩体;上部流体水平运移,没有受到挤压作用,流体逃逸后保留了铁矿的含量,形成了富集的层状铁矿体。这种层状矿体的成因模型类似于透岩浆流体模型。

凹槽结构对水润滑微凹槽尾轴承润滑性能的影响

为研究仿生表面织构占比和宽度对尾轴承润滑特性的影响,基于柔度矩阵法和润滑理论,计入内衬弹性变形,建立表面微凹槽织构水润滑尾轴承的流固耦合模型,通过试验验证模型的正确性和合理性。设计矩形、圆形、等腰三角形3种不同截面形状的微凹槽表面织构水润滑尾轴承,对比分析凹槽占比和宽度对尾轴承承载力和摩擦性能的影响。结果表明:在同等条件下,局部凹槽尾轴承承载力和摩擦性能显著优于全局凹槽尾轴承;凹槽占比约为0.31时,矩形微凹槽尾轴承承载力达到最大值,摩擦因数达到最小值,因此在设计、使用水润滑尾轴承,尤其是赛龙内衬水润滑尾轴承时,建议凹槽占比取值为0.30~0.32,此时可获得最佳润滑性能;随凹槽宽度的增大,局部矩形凹槽尾轴承润滑效果显著优于等腰三角形和圆形凹槽尾轴承。

Marbling计算机仿真技术综述

Marbling是一门在液体表面制作彩色流体状图案的传统手工艺术,Marbling的计算机仿真技术是现今计算机图形学领域中模拟传统绘画方法的一大组成部分.文中对现有的计算机Marbling仿真技术进行了全面的综述,并对它们在模拟方法、模拟对象、实现平台和输出格式等方面进行了详细介绍、分析和对比讨论;将现有仿真方法分为基于物理的模型方法和基于数学的模型方法2类,并介绍了3种不同类型的Marbling纹理图案的模拟技术.最后对全文进行总结,讨论了该领域未来的发展趋势和研究方向.

The Formation of the Jiaodong Gold Province

Gold deposits in Jiaodong,termed Jiaodong-type,are tectonically located in the southeastern margin of the North China Craton.Their major features are reviewed in this paper to highlight the differences between Jiaodong deposits and other genetic types of gold deposits.The mineralization was synchronized with asthenosphere upwelling indicated by synore OIB-like mafic dike and large-scale crustal thinning suggested by decrease of Sr/Y from pre-ore to syn-ore granites.Asthenosphere upwelling induced by the roll-back of Paleo-Pacific Plate drove partial melting of lithospheric mantle and devolatilization,which induced the release of the ore-forming fluids.In concomitant with magmatic records,mineralization migrated from the western Jiaobei terrane(133–127 Ma)to the eastern Sulu orogenic belt(114–108 Ma),corresponding to the eastward roll-back of Paleo-Pacific Plate.Gold mineralization in Jiaodong formed in the transitions of ductile to brittle deformation,rapid to slow crustal uplift,and regional compression to extension.In the regional-scale,the gold deposits in the Jiaobei terrane are mostly situated at intersections between NE-trending faults and EW-trending basement faults,and gold orebodies dominantly controlled by the lithologic contacts between Precambrian metamorphic rocks and Mesozoic granites.The mineralization was dominated by the disseminated-veinlet ores related to quartz–sericite alteration in strong cataclasite-breccia zone,with subsidiary thick quartz-sulfide veins developed in secondary fault zones.The ore-forming fluids belong to a H_(2)O–CO_(2)–NaCl±CH_(4)system and show minor variations in salinity among different types of ore.Structure-fluid feedback involving fluid-rock reaction and hydrofracturing triggered the fluid phase separation and resultant gold deposition.The Jiaodong gold deposits are distinct from orogenic and intrusion-related gold deposits in terms of tectonic setting,origin of ore-forming fluids,and mechanism of gold deposition.

长江三峡导流明渠截流三维动画仿真技术

主要介绍长江三峡导流明渠截流过程的三维动画仿真技术。