Mineralogy and geochemistry of granitoids from Kinnaur region,Himachal Higher Himalaya,India: Implication on the nature of felsic magmatism in the collision tectonics

Felsic magmatism in the southern part of Himachal Higher Himalaya is constituted by Neoproterozoic granite gneiss (GGn), Early Palaeozoic granitoids (EPG) and Tertiary tourmaline-bearing leucogranite (TLg). Magnetic susceptibility values (<3 ×10^?3 SI), molar Al₂ O ₃/(CaO + Na₂ O + K ₂O) (≥1.1), mineral assemblage (bt–ms–pl–kf–qtz ± tur ± ap), and the presence of normative corundum relate these granitoids to peraluminous S-type, ilmenite series (reduced type) granites formed in a syncollisional tectonic setting. Plagioclase from GGn (An₁₀–An₃₁) and EPG (An₁₅–An₃₃) represents oligoclase to andesine and TLg (An₂–An₁₅) represents albite to oligoclase, whereas compositional ranges of K-feldspar are more-or-less similar (Or₈₈ to Or₉₅ in GGn, Or₈₆ to Or₉₇ in EPG and Or₈₇ to Or₉₄ in TLg). Biotites in GGn (Mg/Mg + Fe^t= 0.34–0.45), EPG (Mg/Mg + Fe^t= 0.27–0.47), and TLg (Mg/Mg + Fe^t= 0.25–0.30) are ferribiotites enriched in siderophyllite, which stabilised between FMQ and HM buffers and are characterised by dominant 3Fe\(\rightleftharpoons \)2Al, 3Mg\(\rightleftharpoons \)2Al substitutions typical of peraluminous (S-type), reducing felsic melts. Muscovite in GGn (Mg/Mg + Fe^t=0.58–0.66), EPG (Mg/Mg + Fe^t=0.31?0.59), and TLg (Mg/Mg + Fe^t=0.29–0.42) represent celadonite and paragonite solid solutions, and the tourmaline from EPG and TLg belongs to the schorl-elbaite series, which are characteristics of peraluminous, Li-poor, biotite-tourmaline granites. Geochemical features reveal that the GGn and EPG precursor melts were most likely derived from melting of biotite-rich metapelite and metagraywacke sources, whereas TLg melt appears to have formed from biotite-muscovite rich metapelite and metagraywacke sources. Major and trace elements modelling suggest that the GGn, EPG and TLg parental melts have experienced low degrees (～13, ～17 and ～13%, respectively) of kf–pl–bt fractionation, respectively, subsequent to partial melting. The GGn and EPG melts are the results of a pre-Himalayan, syn-collisional Pan-African felsic magmatic event, whereas the TLg is a magmatic product of Himalayan collision tectonics.     

结合模平方的双树复小波变形监测数据滤波

针对变形监测数据的去噪问题,该文在分析离散小波变换去噪不足的基础上,提出了一种基于模平方的双树复小波变形监测数据滤波方法。该方法利用双树复小波变换的完全重构、近似平移不变性和较好的方向选择性等特点,通过最小尺度空间的小波系数得到噪声强度,并结合模平方处理法确定各层的阈值,经重构阈值处理后的各层小波系数即得到去噪后的信号;经算例,并与传统离散小波变换对比分析。结果表明:双树复小波变换的分解效果优于传统离散小波变换,能较好地表现出细节部分的频率信息,使变形信号的周期性变化特征更为明显。该方法去噪更彻底,进一步提高了消噪的精度和可靠性,可作为变形监测数据降噪处理的新方法。     

西藏雅鲁藏布江缝合带西段普兰纯橄岩中橄榄石的出溶特征及指示意义

西藏雅鲁藏布江缝合带西段普兰纯橄岩中橄榄石存在透辉石和磁铁矿共生出溶现象。这类纯橄岩非常新鲜,主要由橄榄石、尖晶石和透辉石等矿物组成。橄榄石的Fo值是90.1~90.7,铬尖晶石的Cr~#为19.8~20.8,远小于蛇绿岩地幔橄榄岩中常见纯橄岩中铬尖晶石的铬值(Cr~#60)。基于前人研究结果,提出这种现象是由于亏损方辉橄榄岩与含钛、铝、钙熔体发生交代作用,从而形成橄榄石的固溶体存在Ti~(4+)、Al~(3+)、Ca~(2+)、Fe~(3+),而Cr~(3+)进入铬尖晶石结晶。后期由于岩体在抬升过程中降温,橄榄石中出溶形成单斜辉石和磁铁矿,而铬尖晶石结晶被保留。依据铬尖晶石-橄榄石的矿物化学成分,识别出低铬纯橄岩具有最低的部分熔融程度为~8%,Cr~#最高的纯橄岩壳其部分熔融程度达到~50%,表明不同岩相间其形成背景存在明显差异。因此,笔者认为普兰蛇绿岩具有多阶段的过程。首先是在洋中脊环境下经历富Ca、Al和Na等熔体交代和部分熔融作用,后受到俯冲带玻安质熔体改造。     

白缘(鱼央)5S rDNA的扩增分析及其在染色体上的FISH定位

本文分别对雌雄白缘(鱼央)的5S rDNA进行了PCR扩增和序列分析,并采用双色荧光原位杂交(FISH)技术,以白缘(鱼央)的5S rDNA序列和小麦的45S rDNA为探针,对其在白缘(鱼央)雌雄中期染色体上进行了FISH定位研究。结果表明,白缘(鱼央)5S rDNA序列无雌雄差异;5S rDNA的保守区序列为117 bp;5S rDNA和45S rDNA分别被定位于白缘(鱼央)的性染色体和第5号染色体上。同时从GenBank中获得了22种鱼的5S rDNA,运用DNAman软件构建了23种鱼的系统发育树,对白缘(鱼央)的进化地位进行了初步研究。本研究为阐明白缘(鱼央)在鱼类系统进化中的位置、重复序列在脊椎动物性染色体上的分布状况以及与性别决定与分化的关系,提供了资料积累和分析依据。     

半潜平台浮子式系泊系统参数优化研究

通过在系泊缆中设置浮子可以改善系泊系统性能,降低平台运动响应。建立浮子式系泊系统的数值计算模型,验证浮子式系泊系统数值计算方法,详细分析浮子设计参数(设置位置和净浮力大小)变化对系泊缆张力特性与平台运动的影响规律,并根据得到的规律选择了优化的浮子系泊系统方案。最后对优化方案进行评估,表明优化方案可以显著降低系泊中的平台水平运动,尤其是低频运动,同时系泊缆张力变化不大,仍满足安全要求。研究结果可为今后浮子式系泊系统设计提供参考。     

A direction-dependent shear strength criterion for rock joints with two new roughness parameters

The surface morphology of a rock joint is closely related to its mechanical properties. To reasonably characterize a rock surface, two new roughness parameters were proposed in this paper. One is related to the average slope angle of asperities that contribute to the shear strength, and the other reflects the frictional behavior of asperities that is defined as the maximum possible contact area in the shear direction. Taking the standard joint roughness coefficient profiles as example, these two roughness parameters can be applied to describe the directional characteristics of shear strength. Based on their relationships with initial dilation angles, the proposed roughness parameters were incorporated into a peak shear strength criterion. It is shown that the predicted peak shear strength is consistent with experimental data, and there is a power–law relationship. The application range of new roughness parameters was determined, which may facilitate a measurement process.     

云南勐海地区离子吸附型稀土矿控矿因素及找矿前景

云南勐海地区地处临沧-勐海(岩浆弧) Fe-Pb-Zn-Au-Ag-Sn-Sb-Ge-REE矿带(Ⅳ9)南段,近年来该区发现多个离子吸附型稀土矿床。为查明勐海地区离子吸附型稀土矿床控矿因素,指导后续找矿工作,本文在野外地质调查和室内综合整理分析的基础上,对勐海地区离子吸附型稀土矿床的成矿地质背景和成矿特征进行了初步研究,探讨了本区离子吸附型稀土矿床控矿因素与找矿前景。研究表明,勐海地区离子吸附型稀土矿床是以轻稀土为主的稀土矿,其成矿母岩为晚三叠世临沧花岗岩,次生富集成矿于新生代以来;其矿床的形成不仅受成矿母岩、地球化学、构造等内在因素的影响,亦受地形地貌、气候和植被等外在因素的控制,在勐海回龙卡-帕宫苏胡一带形成一条北西-南东向的稀土矿富集带。结合1∶5万矿调工作成果,认为勐海地区成矿地质条件优越,具有很大的离子吸附型稀土矿找矿前景。     

Identifying rainfall threshold of flash flood using entropy decision approach and hydrological model method

Natural Hazards - Flash flood disaster, with strong suddenness and tremendous destructiveness, is one of the most severe natural disasters in China that seriously threaten the lives and property...