黄河三角洲地区末次盛冰期以来浅地层划分与海平面变化的响应

通过对黄河三角洲几个钻孔的分析.将其自上而下划分成3个海相层和3个陆相层,并且划分为1个4级层序(准层序)和4个5级层序。每个层序代表了一次海平面的升降旋回。4级层序的海退沉积与末次冰期的后期对应,海平面下降最大时期是末次冰期最盛期(LGM)的反映。     

陕南公路软弱变质岩边坡变形破坏特征的研究

陕西省是软弱变质岩分布广泛的省份之一。近年来,随着工程建设数量的增多和规模的加大,软弱变质岩斜坡灾害频繁发生,造成的损失也逐年增加。本文通过对陕南316国道早阳-蜀河段的实地调查,归纳了该路段软弱变质岩边坡的变形破坏特征,总结出顺层滑动、弯曲-倾倒、楔形体滑动、溃曲破坏以及滑移-拉裂5种典型的病害模式,并对每种变形破坏模式进行了具体的实例分析,从而为边坡成灾预警和选择经济有效的治理对策奠定基础。     

雅鲁藏布江缝合带造山型金矿床成矿流体特征:来自He-A r同位素的约束

雅鲁藏布江缝合带造山型金成矿带是近些年来在青藏高原新确立的碰撞造山型金成矿带,成矿流体是一套CO2-H2 O-NaCl-CH4-N2体系,以变质水为主.为探讨地幔组分对成矿的影响,本文选取雅鲁藏布江缝合带内邦布矿床和念扎矿床两个大型的造山型金矿为研究对象,对与成矿相关的黄铁矿及胶黄铁矿进行He-Ar同位素分析.结果显示...     

辽东湾中北部浅层埋藏古河道沉积特征及对海上工程的影响

以大量钻孔资料总结出辽东湾中、北部全新世8.5kaB.P.以采沉积了第一海相层,与下伏盛冰期的陆相层之间构成不整合界面(R1).界面以下的B层中发育大量埋藏古河道.古河道NE向展布,宽20～800m,埋深2～13m,按其埋深位置分成4种古河道,按其充填方式又可分成5种古河道.它们在认识地层古环境、海上施工、海上建筑和防灾减灾上有重要意义.     

Structural Evidence for the in-situ Origin of the HP and UHP Eclogites in the Dabie-Sulu Orogenic Belt

Whether the HP and UHP metamorphic rocks of the Dabie-Sulu orogenic belt are of an "in-situ" or "foreign" origin is a long-standing dispute among geologists. Eclogites preserved today in the HP and UHP units constitute merely 5-10%, which are not isolated exotic bodies tectonically intruding into amphibolite facies gneiss, but remnants of once pervasive or widespread eclogite-facies terranes or slabs. The present spatial distribution and forms of the eclogites have resulted from polyphase and progressive deformation and strain partitioning of the HP and UHP slabs. From their formation in deep mantle to their exhumation to the surface, the eclogites have experienced long-term deformation with different strain regimes. The dominant regime responsible for the present spatial distribution and forms of the eclogites is the shear process. The deformation patterns of the eclogites and gneiss matrix also clearly show that the eclogites were metamorphosed in situ. The original distribution area of the eclogites     

实测剖面地层厚度计算方法探讨

实测剖面和地层厚度计算是从事野外地质工作的基本功,以往所使用的计算公式、计算方法和繁琐的查表程序给地质工作者带来许多不便。通过几十年的野外地质工作体验,总结摸索出一套较为简便的计算公式和运算方法。该方法既易于操作,便于在野外和室内使用计算器,提高工作效率,又能提高计算精度。     

Tectonothermal evolution of the gneiss complex at Salur in the Eastern Ghats Grnaulite Belt of India

Textural relations, thermobarometry and petrogenetic grid considerations in the syn-tectonic granitoid massif and the enveloping metasedimentary gneisses at Salur are consistent with a counter-clockwise P–T –t path for the rocks. The low-P/high-T prograde sector is documented by the pre- to syn-D₁ cordierite±orthopyroxene±garnet±spinel–bearing metatexite leucosomes in metapelites. Heating and loading of the rocks (syn- to post-D₁) resulted in the formation of garnet+orthopyroxene± cordierite-bearing diatexites, and decomposition of cordierite in metatexite leucosomes to orthopyroxene+sillimanite+biotite+quartz symplectites. Near-peak temperature, 850 °C at 8.0 kbar, was reached syn- to post-D₂. Post-peak cooling resulted in the stabilization of coronal grossular and anorthite+calcite symplectites at the expense of scapolite+wollastonite+calcite assemblages in calc-silicate gneisses, and the resetting of cation exchange temperatures at 700–750 °C. Near-isothermal decompression at c. 700–750 °C is manifested by the decomposition of garnet porphyroblasts in the granitoid gneisses to plagioclase+orthopyroxene/ilmenite/biotite two-phase coronas and restabilization of cordierite at garnet margins in metapelites. Subsequent low-P, near-isobaric cooling led to the overprinting of granulite facies assemblages by muscovite+calcite assemblages, and further resetting of cation exchange thermometers to lower temperatures c. 600 °C. The tectonothermal evolution of the Salur gneiss complex vis-a-vis the Eastern Ghats Belt is therefore consistent with high degrees of lower crustal melting, followed by prograde heating of the cover rocks due to magma invasion synchronous with crustal compression, and finally thermal relaxation over a protracted period punctuated by tectonic/erosional denudation of the thickened crust.     

Geochemical constraints of the eclogite and granulite facies metamorphism as recognized in the Raobazhai complex from North Dabie Shan,China

A combined study of major and trace elements, fluid inclusions and oxygen isotopes has been carried out on garnet pyroxenite from the Raobazhai complex in the North Dabie Terrane (NDT). Well‐preserved compositional zoning with Na decreasing and Ca and Mg increasing from the core to rim of pyroxene in the garnet pyroxenite indicates eclogite facies metamorphism at the peak metamorphic stage and subsequent granulite facies metamorphism during uplift. A P–T path with substantial heating (from c. 750 to 900 °C) after the maximum pressure reveals a different uplift history compared with most other eclogites in the South Dabie Terrane (SDT). Fluid inclusion data can be correlated with the metamorphic grade: the fluid regime during the peak metamorphism (eclogite facies) was dominated by N₂‐bearing NaCl‐rich solutions, whereas it changed into CO₂‐dominated fluids during the granulite facies retrograde metamorphism. At a late retrograde metamorphic stage, probably after amphibolite facies metamorphism, some external low‐salinity fluids were involved. In situ UV‐laser oxygen isotope analysis was undertaken on a 7 mm garnet, and impure pyroxene, amphibole and plagioclase. The nearly homogeneous oxygen isotopic composition (δ¹⁸O_VSMOW = c. 6.7‰) in the garnet porphyroblast indicates closed fluid system conditions during garnet growth. However, isotopic fractionations between retrograde phases (amphibole and plagioclase) and garnet show an oxygen isotopic disequilibrium, indicating retrograde fluid–rock interactions. Unusual MORB‐like rare earth element (REE) patterns for whole rock of the garnet pyroxenite contrast with most ultra‐high‐pressure (UHP) eclogites in the Dabie‐Sulu area. However, the age‐corrected initial ε_Nd(t) is ? 2.9, which indicates that the protolith of the garnet pyroxenite was derived from an enriched mantle rather than from a MORB source. Combined with the present data of oxygen isotopic compositions and the characteristic N₂ content in the fluid inclusions, we suggest that the protolith of the garnet pyroxenite from Raobazhai formed in an enriched mantle fragment, which has been exposed to the surface prior to the Triassic metamorphism.     

东濮凹陷“高阻红”的地质时代与划分对比

渤海沿岸盆地东濮凹陷内发育的“高阻红”地层的地质时代归属和划分对比问题长期以来一直存在争议。通过区域地层对比、黏土矿物同位素年龄测试、古生物分析和“高阻红”地层赋存状况等的分析,确认该区“高阻红”地质年代属早三叠世,它与华北地区中—西部广泛分布的下三叠统刘家沟组以及和尚沟组可以对比。     

湖南省辰溪县石马湾区段找煤前景浅析

根据石马湾区段所处的区域构造位置,结合岩相古地理及聚煤规律的演化,运用成矿地质理论和方法,对区域内大面积出露的中侏罗统泸阳组地层下隐伏含煤岩系的含煤可能性进行了探讨,预测了区段内江口煤系资源预测量可达5 600万t,对下一步普查找煤工作具有一定的指导意义.