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| 1 | 涪江上游流域盆地地貌特征及构造指示意义显示文摘对涪江上游流域盆地地貌特征及成因进行研究,有助于揭示青藏高原东缘晚新生代以来新构造活动的差异性。本文以ArcGIS水文分析模块为技术平台,在研究区域内系统提取涪江上游流域盆地地表水系网络和涪江干流东西两侧36个亚流域盆地,并对亚流域盆地面积、周长、水系总长度、水系分支比、流域盆地演化阶段进行统计分析,结果表明,涪江干流河道东西两侧典型地貌参数存在显著差异。通过对该区域构造运动、岩石抗侵蚀能力、降水特征等几方面因素与河流下切过程相关性的分析可知,降水条件和岩性差异并不是涪江上游亚流域盆地不对称发育的主要影响因素,该区域断裂活动导致的地形不对称分布格局及岩层破碎程度的差异是涪江上游流域地貌差异演化的主控因素。另外,涪江上游干流展布呈现出两个特征:涪江干流河道因雪山断裂、北川-映秀断裂、彭县-灌县断裂的右旋(或左旋)走滑作用而沿断裂发生同步弯曲;涪江干流河道在北川-映秀断裂北侧由西北-东南流向转变为近正南流向,究其原因,主要是龙门山断裂带3条主干断裂的区域性右旋走滑活动驱动该区域物质产生相应右旋运动,从而使长期处于断层右旋作用控制之下的涪江干流河道发生转向。 | 陈浩 杜华明 董廷旭 李勇 | 2020 | 第四纪研究2020，40，1： | 8 |
| 2 | Concealed porphyry delineation based on nonlinear three-dimensional densitydifference inversion: An example in the Beiya mine area, Western Yunnan, China显示文摘Intermediate acid-complex rock masses with low-density characteristics are the most important prospecting sign in the Beiya area, of western Yunnan province, and provide a physical basis for good gravity exploration. It is usually difficult to obtaining solutions in connection with actual geological situations due to the ambiguity of the conventional gravity-processing results and lack of deep constraints. Thus, the three-dimensional (3D) inversion technology is considered as the main channel for reducing the number of solutions and improving the vertical resolution at the current stage. The current study starts from a model test and performs nonlinear 3D density-difference inversion called “model likelihood exploration”, which performs 3D inversion imaging and inversion of the known model while considering the topographic effects. The inversion results are highly consistent with those of the known models. Simultaneously, we consider the Beiya gold mine in Yunnan as an example. The nonlinear 3D densitydifference inversion technology, which is restricted by geological information, is explored to obtain the 3D density body structure below 5 km in the mine area, and the 3D structure of the deep and concealed rock masses are obtained using the density constraints of the intermediate-acid-complex rock masses. The results are well consistent with the surface geological masses and drilling-controlled deep geological masses. The model test and examples both show that the 3D density-difference nonlinear inversion technology can reduce inversion ambiguity, improve resolution, optimize the inversion results, and realize “transparency” in deeply concealed rock masses in ore-concentrated areas,which is useful in guiding the deep ore prospecting. | Jian Yang Sheng-xian Liang Qiao Wang Wei Zhang Jing Guo Guo-zhong Liao | 2019 | China Geology2019，2，3： | 0 |
| 3 | Timing of Anatexis within the Berere HTHP Complex Belt of Maevatanana Area,North-Central Madgascar,and its Geological Significance显示文摘The Berere HTHP Complex belt in Maevatanana area of north–central Madagascar formed in the^2.5 Ga orogeny and underwent high temperature(up to 1050℃)and high pressure(up to 11.5 kbar)granulite facies metamorphism.Then a widespread anatexis took place and numerous widely distributed felsic leucosomes formed.The majority of these leucosomes are parallel to the schistosity of the complex or are present as stockworks,as thin layers,or as lenses at different scales in the host rocks.Here,we report new petrographic data,zircon LA-ICP-MS U-Pb ages,and Lu–Hf isotopic data for felsic leucosomes within this complex.Anatexis,as identified by the petrological study of felsic leucosomes in the field and in thin sections,involved initial ternary feldspar exsolving to produce antiperthite and a quartz+plagioclase±K-feldspar+sericite mineral assemblage around feldspar grain boundaries.Dissolution is apparent along muscovite grain boundaries,and residual sericite is present around the margins of feldspar and quartz,all suggesting that anatexis was driven by reactions involving muscovite.Zircon U–Pb dating indicates that the felsic leucosomes within the complex formed at 2467–2369 Ma.The majority of samples have positiveεHf(t)values,although a few have negative values,suggesting their formation from magmas predominantly sourced from the depleted mantle,possibly with the involvement of minor amounts of crustal materials.Two-stage Hf model ages andεHf(t)values for these samples are consistent with those for gneisses of the basement,indicating that the felsic leucosomes were formed by the anatexis of gneisses and both of their protolith formed during the formation of continental crust in Meso-Neoarchean(ca.3.1–2.7 Ga).As such,the crystallization age of the felsic leucosome(~2.4 Ga)represents the timing of regional anatexis and a change to post-orogenic tectonism.And this anatexis is also corresponds to the thermal event in Dharwar craton in India which has a pronounced similar Precambrian geology with Madagascar,providing an important constraints on the correlation of the two continental fragments. | LI Peng LIU Shanbao LI Jiankang SHI Guanghai LIU Xiang | 2020 | Acta Geologica Sinica(English Edition)2020，94，5： | 0 |
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