翁泉沟硼铁矿床地质特征

翁泉沟硼铁矿床赋存于早元古宙辽河群里尔峪组。原岩为一套在裂谷环境下形成的中酸性火山岩及碳酸盐岩。矿体的容矿岩石是镁质大理岩。矿体厚度与容矿岩石厚度呈正相关关系。矿石矿物有硼镁石、硼镁铁矿、遂安石等,伴生矿物达64种。根据矿石所含的矿物种类,翁泉沟硼铁矿床矿石类型可分为磁铁矿型、硼镁石型、硼镁石—磁铁矿型、含硼镁铁矿—硼镁石—磁铁矿型等4种类型。硼镁铁矿是在火山喷气和深海沉积作用下形成的层控火山沉积变质矿床。     

Qualitative thermobarometry of inverted metamorphism in the Pelona and Rand Schists, southern California, using calciferous amphibole in mafic schist

Abstract The Rand and Pelona Schists consist of eugeoclinal rock types overlain by continental basement along the Vincent-Chocolate Mountains (VCM) faults. Both schists display inverted metamorphic zonation, defined in part by a systematic variation in composition of calcic to sodic-calcic amphibole in mafic schist structurally upward. The compositional progressions include increase of total A1, A1^IV and Ti, but decrease in the ratios of Na/(Na + Ca) to A1/(A1 + Si), and Na^M4 to (A1^VI+ Fe³⁺+ Ti). These variations imply that structurally high rocks belong to a lower-pressure metamorphic fades series than those at depth. This result is consistent with previous views that the inverted metamorphic zonations represent intact structural sequences.
Amphibole composition is dependent not only on structural position (i.e. P-T ), but also upon bulk-rock composition. The important controls are whole-rock Mg/(Mg + Fe²⁺+ Mn) and Fe³⁺/Fe²⁺. The greatest impact of these factors, however, is on the absolute values of Na and Al, rather than their ratio. Thus, interpretation of facies series is not seriously hindered by compositional variability.
Sodic amphibole in epidote blueschists from the Rand Schist is extensively replaced by sodic-calcic amphibole. Sodic-calcic amphibole in the Rand Schist and Pelona Schist is, itself, rimmed by actinolitic amphibole. Similar blueschist to greenschist transitions in other metamorphic terranes are typically attributed to exhumation. In the Rand and Pelona Schists, the sequence probably formed during burial.     

浙江省萧山—富阳前震旦纪双重基底及构造演化

萧山—富阳一带的前震旦系，分别由中元古代陆缘岛弧型双溪坞群火山岩、新元古代青白口纪河上镇群弧后盆地沉积和双峰式陆相火山岩组成。中元古代末的神功运动表现强烈，青白口纪末的晋宁运动叠加褶皱明显。剖面连续完整，地质现象丰富．是华南重要的层型剖面。     

Preservation of Permo–Triassic low-pressure assemblages in the Cretaceous high-pressure metamorphic Saualpe crystalline basement (Eastern Alps, Austria)

Metapelites and intercalated metapegmatites of the Saualpe crystalline basement, which forms part of the Austroalpine nappe complex in the Eastern Alps, display a polyphase tectonometamorphic history. Here, we focus on the evolution that these rocks underwent prior to Cretaceous (eo‐Alpine) high‐pressure metamorphism and related penetrative deformation. Geothermobarometry on coarse‐grained porphyroclastic parageneses (garnet–biotite–muscovite–plagioclase–sillimanite–quartz), which occur as relics in kyanite–garnet, two‐mica gneiss, yielded 600 °C/0.4 GPa. Results from a corundum‐bearing lithology suggest that higher temperatures may have been reached in very restricted areas. The matrix of these rocks displays intense recrystallization during a pressure‐dominated metamorphic overprint. Microstructures and mineral chemistry indicate that this low‐pressure metamorphism was the first significant metamorphic imprint in these rocks. Mineral relics in all metapelitic rock types reflect low‐pressure conditions for this interkinematic crystallization phase. The distribution, macroscopic and microscopic observations and the mineralogical composition of intercalated metapegmatites point to regionally elevated temperature conditions during their emplacement. Therefore, pegmatite formation is correlated with mineral formation in metapelites. Sm–Nd‐dating of magmatic garnet from the pegmatite gneiss yielded 249 ± 3 Ma, which is interpreted to represent the age of pegmatite‐emplacement and low‐pressure metamorphism in the metapelites. Since the pegmatites are overprinted by mylonitisation and high‐pressure metamorphism, this Permo–Triassic age also sets an upper age‐limit to the eclogite facies metamorphic event, which affected considerable parts of the Saualpe crystalline basement.     

泌阳断陷双河—赵凹地区核三上段陆相层序形成过程的计算机模拟

综合考虑陆源碎屑物供给、内源碳酸盐岩沉积、沉积物侵蚀与再沉积、重力流沉积以及构造升降和水平位移等诸多地质因素 ,建立了一个能够模拟各型盆地的综合数学物理方程式。实际可容空间变化往往由多因素复合作用所致 ,尤其湖平面变化与基底构造沉降的叠合。在综合分析研究区实际地质资料的基础上 ,建立了下第三系核三上段沉积时期湖平面变化及基底构造沉降曲线理论模型 ,并求取了其可容空间变化速率曲线。据此 ,采用自行研制的定量层序地层模拟系统 ,模拟了泌阳断陷双河—赵凹地区下第三系核三上段沉积时期可容空间变化过程与陆相层序响应特征。     

合肥地区地热资源潜力评价

地热资源是宝贵的矿产资源,是一种可再生的,优质、环保、清洁能源。合肥是安徽省省会,经济持续快速发展对清洁地热能源的需求不断增长。据有关资料,合肥地区地处莫霍面隆起区,地壳减薄上地幔隆起是合肥地区地温相对高的大的区域地质背景。合肥西,五十里小庙凸起(合肥地区地垒地段)是基底隆起聚热型地热地质成因模式形成地热的有利地段,可作为今后合肥地区地热资源地质勘查的第一靶区。合肥地区的大地构造环境和深部地壳结构对成热条件较为有利,地热资源的潜力较大。     

超高压变质岩中微粒金刚石的发现及其动力学意义

概述了目前仅有的几个发现微粒金刚石的地区如哈萨克斯坦，挪威西部和我国中等部地的超高压变质岩的最新研究成果，并指出这些变质岩中微粒金刚石为变质成因，变质流体对微粒金刚石的形成具有十分重要的意义。     

华北平原区地温梯度与基底构造形态的关系

本文根据部分实测温度资料和有限单元法的数值模拟计算结果,研究了华北平原区地温梯度和地表热流值与基底构造形态的关系,分析了盖层相对厚度、基岩侧界面倾角以及不同岩石热导率比值对地温梯度和地表热流分布图式的影响,并讨论了地壳浅部热流的折射和再分配问题。在此基础上,提出了华北平原区地温梯度和热流值基底构造形态的相关直线校正法,即根据不同构造部位上钻孔的实测地温梯度和盖层相对厚度的相关直线推算区域平均地温梯度和具代表性区域热流值的方法。     

Acoustic wave scattering from a rough seabed over a sediment layer with generalized-exponential density and inverse-square sound speed profiles

This paper considers acoustic plane wave scattering from a rough seabed on a transition sediment layer overlying an elastic sea basement. The transition sediment layer is assumed to be fluid-like, with density and sound speed distributions behaving as generalized-exponential and inverse-square functions, respectively. This specific class of density and sound speed profiles deserves special attentions not only because it is geologically realistic, but also renders analytical solutions to the Helmholtz equation, making it particularly useful in the study of ocean and seabed acoustics. Based upon a boundary perturbation approach, the computational algorithm for the spatial spectrum in terms of the power spectral density of the scattered field has been developed and implemented. The results have shown that, while the coherent field mainly depends upon the gross structure of the seabed roughness, e.g., RMS roughness, the scattered field is significantly affected by the details of the roughness distributions specialized by the roughness power spectrum and the spatial correlation length of the rough surface. The dependence of the power spectral density of the scattered field on the various types of sediment stratifications, including the constant and the k²-linear sound speed distributions, is also included in the analysis.     

Reaction microstructures in corundum‐ and kyanite‐bearing mafic mylonites from the Takahama metamorphic rocks,western Kyushu,Southwest Japan

High‐grade mylonites occur in the Takahama metamorphic rocks, a member of the high‐pressure low‐temperature type Nagasaki Metamorphic Rocks, western Kyushu, Japan. Mafic layers within the mylonites retain reaction microstructures consisting of margarite aggregates armoring both corundum and kyanite. The following retrograde reaction well accounts for the microstructures in the CaO–Al₂O₃–SiO₂–H₂O system: 3Al₂O₃ + 2Al₂SiO₅ + 2Ca₂Al₃Si₃O₁₂(OH) + 3H₂O = 2Ca₂Al₈Si₄O₂₀(OH)₄ (corundum + kyanite + clinozoisite + fluid = margarite). Mass balance analyses and chemical potential modeling reveal that the chemical potential gradients present between kyanite and corundum have likely driven the transport of the CaO and SiO₂ components. The mylonitization is considered to take place chronologically after peak metamorphism and before the above reaction, based on the following features: approximately constant thickness of the margarite aggregates, random orientation of margarite, and local modification of garnet composition at a boudin neck that formed during mylonitization. The estimated peak temperature of 640°C and the pressure–temperature conditions of the above reaction indicate that the mylonitization took place at temperature between 530 and 640°C at pressures higher than 1.2 GPa, approximately equivalent to the depth of the lower crust of island arcs.