常波况下前滨剖面地形动力过程分析

利用在粤东后江湾多日逐时连续观测的近岸波浪、流、海滩潜水位和海滩前滨剖面地形数据,通过典型相关分析方法提取了占总方差90%以上的4个显著的典型相关变量,进而分别论述了常波况下海滩前滨剖面不同部位的地形动力过程。     

Characterization of the Mefjell plutonic complex from the Sør Rondane Mountains, East Antarctica: Implications for the petrogenesis of Pan-African plutonic rocks of East Gondwanaland

Abstract The Mefjell plutonic complex consists of 500–550‐Ma Pan‐African plutonic rocks, which intrude into the Precambrian crystalline basement in the Sør Rondane Mountains, East Antarctica, and forms part of the Sør Rondane Suture Zone. The complex comprises syenitic and granitic (mostly monzogranitic) rocks, and is characterized by the presence of iron‐rich hydrous mafic minerals and primary ilmenite, both of which imply its formation at high temperature and under low oxygen fugacity conditions. The syenitic rocks are metaluminous, and are high in alkalis, K₂O/Na₂O, Al₂O₃, FeO_t/(FeO_t + MgO) (0.88–0.98), K/Rb (800–1000), Ga (18–28 p.p.m.), Zr (up to 2100 p.p.m.) and Ba. They also have a low Mg? (Mg/[Mg + Fe²⁺]), Rb, Sr, Nb, Y and F, low to moderate light rare earth element (LREE)/heavy rare earth element (HREE) ratios and positive Eu anomalies in their rare earth element (REE) patterns. The granitic rocks are metaluminous to peraluminous, and have a high Rb content, high Sr/Ba and LREE/HREE ratios, low K/Rb and negative Eu anomalies. Most of the syenitic and granitic rocks have Y/Nb ratios greater than 1.2, and are depleted in Nb, Ti and Sr on the primitive mantle‐normalized spider diagrams, indicating a crustal origin with subduction zone signatures. We interpret both the syenitic and granitic rocks to be derived from an iron‐rich lower crustal source by dehydration melting induced by the heat of mantle‐derived basaltic intrusion, after which they then underwent limited fractional crystallization. The Mefjell plutonic complex has a high Zr content and tectonic discrimination diagram signatures indicative of normal A‐type granitic rocks. Both rock suites may have been generated under the same postorogenic tectonic setting. The Mefjell syenitic rocks are chemically comparable to charnockites in the Gjelsvikjella and western Mühlig‐Hofmannfjella areas of East Antarctica, whereas the granitic rocks are comparable to aluminous A‐type granitic rocks in South India, which were emplaced during formation and evolution of the Gondwanaland supercontinent.     

基于Logistic模型的单点下沉预测应用研究

岩层与地表移动具有一定的规律,由于Knothe时间函数虽然可以预计地表下沉,但在预计中有描述地表下沉速度的不足,并且其函数复杂.研究矿区单点动态下沉过程对于地表建筑物的保护具有重要意义,本文采用Logistic模型拟合下沉曲线,得到了预计方程,结果表明预计精度较高.Logistic模型参数少,函数相对简单,计算结果表明...     

鄂尔多斯盆地纳岭沟铀矿床后生蚀变成因及其与铀成矿的关系

鄂尔多斯盆地纳岭沟铀矿床是中国近期落实的又一特大型铀矿床,为古层间氧化带砂岩型铀矿床。根据蚀变作用与成矿作用的关系,建立了新的古层间氧化带砂岩型铀矿床后生蚀变分类方法,即将其划分为控矿蚀变、成矿蚀变和保矿蚀变3类。分别从垂向上和平面上分析了后生蚀变的空间分布规律,剖面自下而上整体表现为保矿蚀变-成矿蚀变-控矿蚀变的垂向序列;平面上重点分析了氧化砂体厚度、氧化砂体百分率、氧化砂体底埋深、氧化砂体底标高等参数特征。     

Obtaining Constitutive Relationship for Rate-Dependent Rock in SHPB Tests

A large number of tests have recently been conducted with the Split Hopkinson pressure bar (SHPB) method to determine the characteristics of rock dynamics. However, it is still impossible to get test results at a perfect constant strain rate from this set-up owing to the rate dependency of rock materials. For instance in most cases, dynamic behavior of rock can only be described with an average strain rate. The results from these methods, including rich strain rate information, frequently tend to be inexplicable or self-contradictory. The obtained stress–strain curves can then never be directly treated as constitutive curves as in static tests. In this paper, the reasons behind the controversial stress–strain results with current methods are analyzed. In addition, the requirement for the rock specimen to deform at a constant strain rate is demonstrated after theoretical analysis of correlations among specimen, deforming stress, incident stress, reflected stress and transmitted stress. With test results from SHPB by pulse shaper and special shape striker methods, the requirement is verified. Finally, the method of 3D scattergram considering stress–strain–strain rate simultaneously is brought up to get constitutive relationships of rate-dependent rock. The new method gives reasonable predictions for constitutive relationships of rock at different strain rates. At the same time, the new method has fewer requirements and has a wider application scope for SHPB tests.     

广邻路华蓥山特长隧道岩溶地质问题与对策

公路、铁路等线路穿越岩溶地区时,合适的选线方法可降低工程造价、减少工程病害及环境影响,从而科学解决穿越与避让问题。拟建广安至邻水公路为双向四车道一级公路标准,初步设计阶段在工程可行性研究基础上采用低线A线和高线K线方案进行研究。华蓥山特长隧道穿越岩溶地区,为本项目的控制性工程。以华蓥山特长隧道为研究对象,在充分收集既有G42沪蓉高速华蓥山隧道相关资料的基础上,通过分析岩溶区岩溶发育规律、水文地质特点和岩溶地区公路选线的相关要点,采用多种辅助技术,总结出选线原则,最终推荐K线方案为总体最优方案。通过此工程实例,提出在复杂地质岩溶区公路选线的过程中要遵守“多比选,慎选择”的原则、践行地质环保选线原则和“以避为主,避重就轻,动态设计”的设计要点。      

Petrology and mineralogy of mesosiderite Northwest Africa 12949: Implications for geological history on its parent body

Mesosiderites are breccias composed of roughly equal parts of metal phases and silicate clasts. However, the parent body and formation process of mesosiderites remain enigmatic. Northwest Africa (NWA) 12949 is a newly found mesosiderite belonging to type 2A. One type of ultramafic clasts and four types of mafic clasts (gabbroic, poikilitic, subophitic, and cataclastic), compositionally consistent with diogenites and eucrites, have been identified in NWA 12949. However, these clasts have undergone different thermal histories, with cooling rates varying from ~0.0044 °C year⁻¹ to a few °C h⁻¹, and equilibrium temperatures varying from ~880 to 910 °C to ~1000 to 1100 °C. All the lithic clasts have undergone redox reactions during extensive metamorphism, forming excess troilite, chromite, merrillite, tridymite, and pyroxene with lower Fe/Mg and Fe/Mn. The petrology and mineralogy of NWA 12949 support a formation scenario involving two major impact events, and a candidate parent body of 4 Vesta.     

积雪水热迁移机理与模型研究进展

积雪是陆地水文循环以及大气过程的重要组成部分,它调节了陆地和大气之间的能量交换,对下垫面的能量收支平衡与水热迁移起重要作用。在介绍积雪特性参数确定方法及积雪水热运移规律的基础上,对国内外现有积雪模型进行了分类和总结,并指出未来在积雪特性参数化方案、数值模拟计算、尺度转换等方面还应进行更深入的研究。     

Geochemical study of Cretaceous magmatic rocks in Chuzhou region,low Yangtze River metallogenic belt: implications for petrogenesis and Cu–Au mineralization

ABSTRACT

The low Yangtze River metallogenic belt (LYRMB) is one of the most important poly-metal deposit belts in China. The Chuxian, Machang and Shangyaopu intrusions in the LYRMB are intermediate rock series, mainly composed of monzonite and quartz monzonite. In this study, bulk rock major and trace elements, zircon U–Pb dating and Hf isotope were analysed. Five ages have been obtained as (1) Chuxian, 121.8 ± 1.9 and 124.0 ± 1.4 Ma, respectively, (2) Machang intrusion, 123.1 ± 2.0 Ma and (3) Shangyaopu, 126.6 ± 1.8 and 123.4 ± 1.9 Ma, indicating that the regional igneous activity was in Early Cretaceous, being consistent with the massive Yanshanian magmatic events in eastern China. These three intrusions are identified as a high-Mg adakite, most of them showing geochemical features of high Si, high Na and low Sr, which can be interpreted as partial melting of subducted oceanic crust. High Mg# characteristics indicate the magmas reacted with the mantle. The negative zircon ε_Hf values of these adakites suggest that the magmas have assimilation of old crustal material, e.g. Archaean continental crust, the basement of the south Tancheng–Lujiang (Tan–Lu) fault. Biotite Ti temperature result (about 700°C) shows that intrusive magma has a relatively low temperature. Petrogenesis and regional Cu–Au mineralization mechanism may be explained by Pacific plate subduction during about 125–180 million years subducted to southwest towards the LYRMB. Magmas formed by partial melting of subducted oceanic crust have systemically high Cu–Au contents, which are conducive to corresponding mineralization.     

Petrology and geochemistry of ultrahigh‐temperature granulites from the South Altay orogenic belt,northwestern China: Implications for metamorphic evolution and protolith composition

Ultrahigh‐temperature (UHT) granulites in the South Altay orogenic belt of Northwestern China provide important clues for the lower crustal components and tectonic evolution of the Central Asian Orogenic Belt during the Paleozoic. In this paper, we studied whole‐rock geochemistry and mineral characteristics to understand the protolith and metamorphic evolution of the Altay UHT granulite. The Altay granulite shows negative discriminant function values (DF) of ?9.27 to ?3.95, indicating a sedimentary origin, probably an argillaceous rock. The peak metamorphic temperature–pressure conditions of 920–1010 °C and > 9 kbar were estimated from the geothermobarometry, together with the stability of spinel (low ZnO) + quartz and orthopyroxene (Al₂O₃ up to 9.2 wt.%) + sillimanite + quartz in the Altay UHT rock, indicate a UHT metamorphic condition has been achieved. Two stages of retrograde conditions are recognized in these rocks; the first is an isothermal decompression to approx. 750 °C at 5.2–5.8 kbar at the early stage, and the second is the cooling down to 520–550 °C at 4.8–5.2 kbar. Combined with previous study, the formation of the Altay UHT pelitic granulite with a clockwise retrograde P–T path is inferred to be related with collisional and accretional orogenic process between the Siberian and Kazakhstan–Junggar plates.