高原寒冷区地电化学提取技术试验与找矿预测

为确定地电化学提取技术在高原寒冷区的最佳工作技术条件,选择在已有工程控制的青海尕大阪铜多金属矿7线剖面,进行地电化学提取技术的对比试验,确定一套适合高原寒冷区的地电化学提取技术。通过对比试验选定其技术指标为:提取时间48 h、供电电压9 V、提取液硝酸浓度15%、提取液用量1000 m L、提取极距1 m、提取材料为经处理过后的泡塑。采用优选的工作技术条件,在矿区东南部未知区域开展隐伏矿勘查预测,圈出了4个有利成矿靶区,指导矿区下一步找矿工作部署。     

基于深度神经网络的蒙古国色楞格河流域水体信息提取

蒙古高原地处干旱半干旱地区,河流水系对该区域的资源环境格局及其生态环境影响重大。发源于蒙古国的色楞格河是蒙古高原最主要的水资源来源,准确掌握该流域的水体信息对东北亚地区生态环境问题及资源保护具有重要意义。本文以蒙古高原色楞格河流域为研究对象,基于谷歌地球引擎（Google Earth Engine,GEE）云平台,使用 Sentinel-2 多光谱卫星遥感影像,利用深度神经网络（Deep Neural Network, DNN）方法对色楞格河流域的水体信息进行提取,并与支持向量机方法进行对比;利用全球30 m SRTM数据生成水系分布矢量图,通过空间分析形成河流提取目标区,结合深度神经网络分类结果,绘制蒙古国色楞格河流域2019年河流分布图。研究结果表明：① 该方法能够准确地完成大流域范围内的水体制图,提取结果能够体现色楞格河流域河流的空间分布,且能够减少河流断流、空洞现象;② 深度神经网络模型中批量大小设置为8时,在处理数据速度与精度中达到最优,而神经网络结构中隐含层数达到4层时,在精度评价指标测试数据集上达到0.9666,保证了模型特征挖掘能力;③ 经样本点的验证,结果总体精度达到97.65%,可以满足实际应用需求。本研究预期可以为蒙古高原的水体提取提供方法支持和相关数据支持。     

基于H-C方法的地震断层面快速识别方法研究——以2021-05-22青海玛多MS7.4地震为例

基于震后各机构给出的玛多M_S7.4地震震源机制解,利用震源-矩心(H-C)方法对地震发震断层进行快速判断,在不需要参考余震情况下,快速识别地震破裂方向。18组测定结果均显示,NWW走向的节面Ⅰ为发震断层面。综合利用震源区地质构造特征、震后余震序列分布、区域构造应力场、烈度等震线以及野外地质考察结果,验证断层测算结果的准确性,最终推断玛多M_S7.4地震断层面为NWW走向的节面Ⅰ、昆仑山口-江错断裂为发震断层,震源机制解显示是一次以左旋走滑为主的地震事件。     

青藏高原的隆升缩短及其粘弹性形变分析

本文依据新生代以来喜马拉雅和青藏高原发生的强烈的构造形变特征,用二维粘弹性有限元数值方法模拟估算了在印度板块向北推挤欧亚大陆的动力条件下,高原各构造单元的形变速率以及由此推算出40Ma以来青藏高原的隆升量和缩短量。反演了各地体岩石力学参数,特别是有效粘性系数η的数量级。认识到物性参数对构造应力场和形变速率的极重要的影响作用。阐明了除了动力机制和边界条件外,岩石圈各圈层材料力学性质的不均一是造成位移场、应力场和形变速率的差异,从而引起各种复杂地质构造现象的基本因素之一。      

青藏高原第四纪大陆冰盖对高原隆升的影响

本文依据在青藏高原存在第四纪大陆冰盖的基础上,给定了3个不同厚度的冰盖,应用弹性板模式模拟计算了大陆冰盖消融前后的地壳均衡过程。计算结果表明,由大陆冰盖消融可能引起的高原隆升最大不超过700m。因此,就整个高原的隆升幅度来说可忽略其影响。但由于冰川消融前后高原负荷发生了变化,导致了隆升速度的相应变化,因而引起地表侵蚀强弱程度的不同及其它一些地质现象是不能忽视的。     

青藏高原沙区地温研究

青藏高原沙区测温结果表明:沙丘下和厚沙层覆盖地段下的地温较邻近天然无沙地表有所升高,而薄沙层覆盖地段下的地温反而比天然无沙地表有降低的趋势。     

Cenozoic reactivation along the Late Triassic Ganzi-Litang suture,eastern Tibetan Plateau

The spatial-temporal development of Cenozoic reactivation along Mesozoic suture zones in the Tibetan Plateau are first-order parameters needed for assessing models of plateau growth. The Ganzi-Litang suture, in the eastern Tibetan Plateau, developed in the Late Triassic because of subduction and closure along the eastern branch of the Paleo-Tethys Ocean. Near the city of Litang, the Ganzi-Litang suture is defined by a mélange sequence with fault-bound, synorogenic nonmarine strata along the western and eastern flanks, suggesting post-Triassic structural reactivation. We present detrital zircon U–Pb geochronology and field data to determine the timing and style of reactivation along the Ganzi-Litang suture, as well as sedimentary provenance of nonmarine strata.A reverse fault placing mélange rock on top of nonmarine strata along the eastern flank of the Ganzi-Litang suture indicates a contractional deformational regime during reactivation. Conglomerate clast counts indicate a local sediment source of recycled Ganzi-Litang suture and Yidun terrane rock. Detrital zircons indicate a localized provenance consisting of recycled material from Triassic Yidun Arc plutons and Triassic Yidun Group turbidite rock. A weighted mean average of Cenozoic zircon grains (n ​= ​10) establishes a maximum depositional age of 41.5 ​± ​1.2 ​Ma for nonmarine strata in the Ganzi-Litang suture. We interpret the maximum depositional age of the nonmarine strata to represent the upper-limit for structural reactivation along the Ganzi-Litang suture while undeformed Neogene strata in the suture zone represent the lower-limit; thereby bracketing structural reactivation from ca. 42–25 ​Ma. Our results provide enhanced spatial-temporal resolution for Cenozoic deformation in the eastern Tibetan Plateau.     

Crustal structure of northeastern Tibetan plateau and Ordos block: Waveform interpretation of the Maqen-Jingbian seismic refraction profile

The Maqen-Jingbian wide-angle seismic reflection and refraction experiment was carried out in 1998, which aims at determining detailed structure in the crust and top of the upper mantle and understanding structural relation between the northeastern Tibetan plateau and the Ordos block. The 1-D crustal models inferred by waveform inversion show strong variations in crustal structure, which can be classified into four different types: ① an Ordos platform with the Proterozoic crust and two high-velocity layers in the northeast section, ② a transitional crust between the northeastern Tibetan plateau and the Ordos block across the Haiyuan earthquake zone, ③ the Qilian orogenic zone in the central part, and 4 the Qinling orogenic zone in the southwestern section. The Moho depth increases from ~42 km to ~62 km from the NE part to the SW part of the profile. The crystalline crust consists of the upper crust and lower crust in northeastern Tibetan plateau. There is an obviously low P-wave velocity layer dipping northeastward, which is 12–13 km thick, at the bottom of the upper crust in Qinling orogenic zone and Haiyuan earthquake zone. The lower crust is characterized by alternating high and low P-wave velocity layers. Beneath Ordos block, i.e., the NE part of the profile, the crust shows quite a smooth increase in P-wave velocity down to the Moho at a depth of about 42 km.     

200-kg large explosive detonation facing 50-km thick crust beneath west Qinling,northeastern Tibetan plateau

It is difficult to acquire deep seismic reflection profiles on land using the standard oil-industry acquisition parameters. This is especially true over much of Tibetan plateau not only because of severe topography and rapid variation of both velocity and thickness of near-surface layer, but also strong attenuation of seismic wave through the thickest crust of the Earth. Large explosive sources had been successfully detonated in US, but its application in Tibetan plateau rarely has an example of good quality. Presented herein is the data of a 200-kg single shot we recorded in west Qinling, northeastern Tibetan plateau. The shot gather data with phenomenal signal-to-noise ratios illustrate the energy of the PmP phase. Although the observations are only limited to the northeastern Tibetan plateau and thus cannot comprise an exhaustive study, they nevertheless suggest that large explosions may be a useful exploration tool in Tibetan Plateau where standard seismic sources and profiling methods fail to produce adequate data of low crust.     

“上山”找金铜, “下山”找钨锡及其理由

金铜和钨锡是两种不同类型的矿产资源, 金铜经常伴生, 钨锡经常伴生, 金铜和钨锡通常不在一起.研究表明, 金铜主要与埃达克岩和喜马拉雅型花岗岩有关, 产于加厚的地壳底部, 地表相应的出现高原或山脉; 钨锡主要与南岭型花岗岩有关, 代表减薄的陆壳, 产于平原区, 地势较低.因此, 从找矿的角度来说, 应当“上山”找金铜, “下山”找钨锡.文中识别出中国三叠纪以来可能存在过的7个山脉(华北北部山脉、西秦岭-东昆仑山脉、额尔古纳山脉、松潘-中甸山脉、湘赣山脉、浙闽山脉和哀牢山-羌塘山脉) 和2个高原(中国东部高原和湖南山地) 以及现存的青藏高原, 建议在上述高原和山脉上去找金铜矿, 指出喜马拉雅型花岗岩与金矿的密切关系, 是今后找金矿的一个重要目标.认为钨锡成矿目前仍然以华南为最佳, 但应注意在其他地块寻找钨锡的问题.