钻孔灌注桩施工常见事故及处理

根据钻孔灌注桩施工过程中常见的八类施工事故，提出了相应的预防及处理方法，特别对掉导管及堵管严重的灌注桩，建议采用二次剪球方法接桩，并详细介绍了接桩时机、操作程序及方法。     

In situ calcite U−Pb geochronology by high-sensitivity single-collector LA-SF-ICP-MS

Science China Earth Sciences - U?Pb geochronology of calcite using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an emerging method, with potential applications...     

Methodology for in situ wolframite U-Pb dating and its application

Tungsten(or wolfram,W),one of the crucial metal sources,is widely used in electronics,oil,chemical and military industries.China owns abundant tungsten resources(~60%of the world reserves and~80%of the world’s production),of which the area from Southern Jiangxi-Northern GuangdongSouthern Hunan is the most significant ore belt in south China.Understanding ore genesis and distribution as well as the process of fine mineralization will further benefit the prospecting and exploration of tungsten deposits.The accurate determination of the age of mineralization is at the front line in the study of ore deposit and the premise for solving and understanding the above problems.     

Geochemical signature of porphyries in the Baogutu porphyry copper belt, western Junggar, NW China

The Baogutu porphyry copper belt lies in the Darbut transitional island arc of the western Junggar, in the western section of the Central Asian Orogenic Belt in NW China. Our new petrographic results for the ore-bearing porphyry stocks in the Baogutu porphyry copper belt recognize them as diorite porphyry stocks rather than the granodiorite porphyry stocks as previously identified. The copper mineralization is hosted in the diorite, diorite porphyries and related breccias of the diorite porphyry stocks.Geochemical data indicate that the ore-bearing porphyries have a predominantly intermediate composition with a transitional character from tholeiite to calc-alkaline, and are enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE) with a clear negative Nb anomaly. REE patterns show distinct enrichments in LREE relative to HREE. The rocks also exhibit high initial εNd(t) (+ 2.7 to + 6.3) ratios and low initial ⁸⁷Sr/⁸⁶Sr values (0.70359–0.70397). Many samples are chemically similar to adakites (e. g. Yb < 1.9 ppm, Y < 18 ppm, Sr/Yb > 20, ⁸⁷Sr/⁸⁶Sr < 0.7045). These data are consistent with a transitional island arc from immature arc to mature arc and suggest that the ore-bearing porphyry system was derived from the partial melting of multiple sources including oceanic crust and a subduction-modified mantle wedge, with melts undergoing significant crystal fractionation during convergence between the paleo-Junggar ocean and the Darbut arc.     

Functional zoning and space management of Three-River-Source National Park

Journal of Geographical Sciences - Functional zoning is a key step for the integrated planning and scientific management of a national park. Selecting the Three-River-Source National Park (TNP) as...     

Evaluation of intensive urban land use based on an artificial neural network model: A case study of Nanjing City,China

In this paper, the artificial neural network (ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the comprehensive, spatial and complex nature of urban land use. Through a preliminary calculation of the degree of intensive land use of the sample area, representative sample area selection and using the back propagation neural network model to train, the intensive land use level of each evaluation unit is finally determined in the study area. Results show that the method can effectively correct the errors caused by the limitations of the model itself and the determination of the ideal value and weights when the multifactor comprehensive evaluation is used alone. The ANN model can make the evaluation results more objective and practical. The evaluation results show a tendency of decreasing land use intensity from the core urban area to the periphery and the industrial functional area has relatively low land use intensity compared with other functional areas. Based on the evaluation results, some suggestions are put forward, such as transforming the mode of urban spatial expansion, strengthening the integration and potential exploitation of the land in the urban built-up area, and strengthening the control of the construction intensity of protected areas.     

湖南保靖区块海相页岩气快速钻探技术

湖南保靖页岩气勘查区块黑色页岩沉积发育,是页岩气勘探开发的有利区带。由于储层埋藏深、地层高陡、地层倾角变化大、岩石可钻性差,导致钻井周期长、成本高等问题。钻前对已有的地震、测井、岩心实验等资料的处理和分析,通过优化井身结构、钻头选型、钻具组合优选和中长筒取心等,实现了保靖区块海相页岩气快速钻探。     

大陆岩石圈地幔定年

大陆岩石圈地幔是伴随地壳熔体抽取而形成的低密度地幔残留,是联系软流圈与地壳的重要纽带。虽然大陆岩石圈地幔一直是固体地球科学研究的重要内容,但对其形成时代的准确厘定则是当前研究的难点。传统方法是采用岩石圈地幔中橄榄岩主要元素的贫瘠程度来对岩石圈进行定年,即古老的岩石圈地幔Al2O3和CaO含量低,而MgO含量高(同时导致橄榄石高Fo值),而年轻岩石圈地幔的特征正好相反。显然,这种间接的方法不能给出确切的年龄信息。尽管Sr-Nd和锆石U-Pb等同位素方法也被用来进行地幔橄榄岩定年,但岩石圈地幔通常具有的较高温度使上述同位素体系不能保持封闭,因而给出的年龄大多与岩石圈地幔的形成时代无关。近几年发展起来的Re-Os同位素技术是目前进行岩石圈地幔定年的最理想工具,但也存在一系列需要研究的问题。文中对这一方法的基本原理、发展现状和存在的问题进行了全面的介绍。同时,根据目前获得的Os同位素资料,对中国东部岩石圈地幔的时代进行了讨论,并简要论述所获得的资料对岩石圈减薄研究的启示。     

Precise Determination of Sm and Nd Concentrations and Nd Isotopic Compositions in Highly Depleted Ultramafic Reference Materials

In this study, a high‐precision method for the determination of Sm and Nd concentrations and Nd isotopic composition in highly depleted ultramafic rocks without a preconcentration step is presented. The samples were first digested using the conventional HF + HNO₃ + HClO₄ method, followed by the complete digestion of chromite in the samples using HClO₄ at 190–200 °C and then complete dissolution of fluoride formed during the HF decomposition step using H₃BO₃. These steps ensured the complete digestion of the ultramafic rocks. The rare earth elements (REEs) were separated from the sample matrix using conventional cation‐exchange chromatography; subsequently, Sm and Nd were separated using the LN columns. Neodymium isotopes were determined as NdO⁺, whereas Sm isotopes were measured as Sm⁺, both with very high sensitivity using single W filaments with TaF₅ as an ion emitter. Several highly depleted ultramafic rock reference materials including USGS DTS‐1, DTS‐2, DTS‐2b, PCC‐1 and GSJ JP‐1, which contain extremely low amounts of Sm and Nd (down to sub ng g^?1 level), were analysed, and high‐precision Sm and Nd concentration and Nd isotope data were obtained. This is the first report of the Sm‐Nd isotopic compositions of these ultramafic rock reference materials except for PCC‐1.     

Determination of Sm‐Nd Isotopic Compositions in Fifteen Geological Materials Using Laser Ablation MC‐ICP‐MS and Application to Monazite Geochronology of Metasedimentary Rock in the North China Craton

In this study, we report both ¹⁴³Nd/¹⁴⁴Nd and ¹⁴⁷Sm/¹⁴⁴Nd values in twelve minerals (apatite, titanite, monazite and eudialyte) based on analyses over 4 years using LA‐MC‐ICP‐MS. The positive correlation between the measured β_Sm and β_Nd (r² = 0.9981) over this time in our laboratory demonstrates the excellent long‐term stability of the method. Compared with the normal method, Sm and Nd signal intensities were improved by a factor of 2.9 with the use of X skimmer and Jet sample cones in combination with the addition of nitrogen at 3–6 ml min^?1 to the central gas flow. The enhancement of signal intensity benefits the accurate in situ determination of the Sm‐Nd isotopes of samples poor in these elements. ¹⁴³Nd/¹⁴⁴Nd values were also determined in two manganese nodules and GSMC Co‐rich crust with low mass fractions of Nd (94–293 μg g^?1). Generally, most of the obtained Sm‐Nd isotopic compositions in these geological materials are consistent with published values. ‘External reproducibility’ (2s) of ¹⁴³Nd/¹⁴⁴Nd and ¹⁴⁷Sm/¹⁴⁴Nd was typically better than 0.06‰ and 2.5‰, respectively, demonstrating that the Durango, Otter Lake, NW‐1 and MAD apatites, the Khan, and OLT‐1 titanites, MGMH#117531 monazite and LV01 eudialyte are promising candidate reference materials for in situ Sm‐Nd isotopic determinations. The Trebilcock, Mae Klang and 44069 monazites are only suitable for in situ Nd isotopic determinations because of their heterogeneous Sm/Nd compositions. The heterogeneous Sm‐Nd composition of titanite BLR‐1 demonstrates that it is not a suitable reference material for in situ Sm‐Nd isotopic determinations. Deep‐sea samples (NOD‐A‐1 and NOD‐P‐1 manganese nodule, GSMC Co‐rich crust) with low mass fractions of Nd also show homogenous Nd isotopic compositions. Sm‐Nd isotopic ratios of a monazite (MQG‐22) from the North China Craton were measured as a case study and gave a ¹⁴⁷Sm‐¹⁴³Nd isochron age of 1792 ± 35 Ma (MSWD = 3.2) consistent with the published metamorphic age of the host metasedimentary rocks. The results for both candidate reference materials and geological samples demonstrate that the in situ LA‐MC‐ICP‐MS analytical protocol described is feasible and robust for research in geological evolution.