Insights into the evolution of the Thomson Orogen from geochronology,geochemistry, and zircon isotopic studies of magmatic rocks     

A. J. Cross  D. J. Purdy  D. C. Champion  D. D. Brown  C. Siégel  R. A. Armstrong 《Australian Journal of Earth Sciences》2013,60(7-8):987-1008

Abstract

Zircon U–Pb ages, εHf(t), and δ¹⁸O isotopic data together with geochemistry and limited Sm–Nd results from magmatic rocks sampled in deep-basement drill cores from undercover parts of the Thomson Orogen provide strong temporal links with outcropping regions of the orogen and important clues to its evolution and relationship with the Lachlan Orogen. SHRIMP U–Pb zircon ages show that magmatism of Early Ordovician age is widespread across the central, undercover regions of the Thomson Orogen and occurred in a narrow time-window between 480 and 470?Ma. These rocks have evolved εHf(t)_zrn (?12.18 to ?6.26) and εNd (?11.3 to ?7.1), and supracrustal δ¹⁸O_zrn (7.01–8.50‰), which is in stark contrast to Early Ordovician magmatic rocks in the Lachlan Orogen that are isotopically juvenile. Two samples have late Silurian ages (425–420?Ma), and four have Devonian ages (408–382?Ma). The late Silurian rocks have evolved εHf(t)_zrn (?6.42 to ?4.62) and supracrustal δ¹⁸O_zrn (9.26–10.29‰) values, while the younger Devonian rocks show a shift toward more juvenile εHf(t)_zrn, a trend that is also seen in rocks of this age in the Lachlan Orogen. Interestingly, two early Late Devonian samples have juvenile εHf(t)_zrn (0.01–1.92) but supracrustal δ¹⁸O_zrn (7.45–8.77‰) indicating rapid recycling of juvenile material. Two distinct Hf–O isotopic mixing trends are observed for magmatic rocks of the Thomson Orogen. One trend appears to have incorporated a more evolved supracrustal component and is defined by samples from the northern two-thirds of the Thomson Orogen, while the other trend is generally less evolved and from samples in the southern third of the Thomson Orogen and matches the isotopic character of rocks from the Lachlan Orogen. The spatial association of the Early Ordovician magmatism with the more evolved metasedimentary signature suggests that at least the northern part of the Thomson Orogen is underlain by older pre-Delamerian metasedimentary rocks.  相似文献   

基于模板的钻孔柱状图自动成图的实现     

施丽军  毛先成  刘京 《地质找矿论丛》2013,28(4):576-581

文章论述了基于模板的钻孔柱状图自动成图方法.首先将钻孔柱状图样式信息存储在预先设计的模板表中,利用模板表中的样式信息绘制钻孔柱状图框架;然后根据模板表中的记录值读取钻孔数据库中相应的钻孔属性,调用MAPGIS SDK绘图接口实现钻孔柱状图的自动成图.此方法可使用户可以根据需要自由地定义钻孔柱状图的样式和需要绘制的信息,极大地满足了实际工作中对同一套钻孔数据生成不同形式柱状图的需求.  相似文献   

吉林省通化县新华矿区多金属矿钻探施工技术     

高贵山  张延龙  纪楠  徐捷伟 《吉林地质》2013,(3):119-123

针对吉林省通化县新华矿区的钻探施工提出了相应的技术措施,主要是施工设备的选择,钻孔结构、钻进方法及钻进参数的选择,钻进技术和措施,冲洗液的选择及管理,保证施工质量措施等方面。通过这些技术措施的实施,顺利的完成了该矿区的钻探施工任务。  相似文献   

软土地区提高旋挖钻机成孔质量的措施          下载免费PDF全文

王文明 《探矿工程》2013,40(9):68-71

针对某高架桥工程采用旋挖钻机在软土层钻进中发生的孔口坍塌、缩径、钻头打滑、孔底沉渣厚度大等情况,进行了原因分析,并采取了加长护筒、改进钻头结构、优化钻进工艺、气举反循环清孔、泥浆净化等针对性措施,取得了良好的效果,确保了工程质量,提高了施工效率,施工经验可供类似工程参考。  相似文献   

立轴式岩心钻机转速检测方法的改进          下载免费PDF全文

尹崧宇  赵大军  郭威  孙友宏  刘华南  孙梓航 《探矿工程》2013,40(12):32-35

立轴式岩心钻机是岩心钻探工程中应用最广泛的钻机。对立轴式岩心钻机转速检测方法进行改进,并且研制了以传感器、计数器模块和采集机为核心的钻机转速检测系统。对转速检测系统中的计数器模块进行优化设计,提高了转速测量的准确性。经漠河盆地天然气水合物钻探试验井的应用,系统工作准确可靠,满足使用要求。  相似文献   

Cooling effect of convection-intensifying composite embankment with air doors on permafrost     

Hong Sun  XiuRun Ge  FuJun Niu  Ge Liu  JinZhao Zhang 《寒旱区科学》2014,6(4):0372-0377

One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.  相似文献   

火山喷发对辐射传输影响的研究     

周清波 《地理研究》1993,12(3):19-25

本文根据火山灰粒子的辐射光学特性,计算了火山灰粒子和平流层本底的辐射光学参数。另外,采用大气多次散射的辐射传输方程,计算了火山喷发对大气辐射变温的影响效果。结果表明,与平流层本底相比,火山灰粒子具有很强的吸收性。火山喷发使平流层吸收太阳辐射增温,并使到达对流层和地面的太阳辐射减少;同时,对大气长波冷却率的影响甚微。  相似文献   

Simulation and causes of eastern Antarctica surface cooling related to ozone depletion during austral summer in FGOALS-s2     

Jing Yang  Qing Bao  Duoying Ji  Daoyi Gong  Rui Mao  Ziyin Zhang  Seong-Joong Kim 《大气科学进展》2014,31(5):1147-1156

Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.  相似文献   

三维技术辅助设计地下管道内套新管的应用     

王涛  张毅  徐莹 《测绘科学技术学报》2014,(5)

既有管道由于自身弯曲和多处沉降导致其三维模型十分复杂,常用的三维管道设计软件不可用,若以测量的纵断面图为依据进行平面层次的设计则存在极大的不可靠性,因而只能利用计算机三维图形技术解决。这里研究采用三维技术辅助既有地下给排水管道内套新管的设计,用三维碰撞检测算法来趋近获取最大管径,并采用基于四元数的球面线性插值法进行三维圆弧的拟合,从而实现对复杂管道的三维建模。采用基于三角形单元的碰撞检测方法,具有简便、适用的特点。基于高效三维引擎Open Scene Graph开发了三维建模及碰撞检测演示软件并对某设计项目进行察看、验证,证实了此方法的正确性。  相似文献   

基于skyline的管线接头自动建模     

吕国胜  李兆雄 《地理空间信息》2013,(3):135-137

在skyline平台进行地下管线的自动建模时,接头处的弯管skyline没有合适的方案实现。鉴于此,通过数学方法,自动进行弯管接头的建模,使在skyline中进行管线系统开发时,弯管接头有了一种可选的建模方案。  相似文献