粤东鸿沟山金矿区流纹斑岩锆石SHRIMP U-Pb定年、Lu-Hf同位素组成及其地质意义

鸿沟山矿区位于华南粤东莲花山钨矿床的中部,是近年来通过地质矿产调查新发现具有找寻金矿潜力的矿床之一。本文以与鸿沟山金等多金属矿化关系密切的流纹斑岩为研究对象,开展了锆石SHRIMP U-Pb定年、流纹斑岩和矿石岩石地球化学、锆石Lu-Hf同位素组成特征研究。获得流纹斑岩锆石206Pb/238U加权平均年龄为169.1±1.5Ma,说明岩体形成于中侏罗世。在微量元素特征方面,流纹斑岩都表现为相对亏损大离子亲石元素Ba、Sr和高强场元素Nb、P、Zr、Hf,富集大离子亲石元素Rb,高强场元素U、Ce、Sm和轻稀土元素La、Nd,流纹斑岩与矿石稀土元素特征基本相似,Eu具中等负异常,但随着矿化强度的增强稀土元素更加富集。流纹斑岩εHf(t)(-15.0~2.2)分布范围宽,二阶段模式年龄TDM2主要变化范围为0.82~0.93 Ga,表明成岩物质主要来源于新元古代古老地壳变质泥岩和变质砂岩部分熔融,并有幔源物质的加入。因此,围绕着该时间段的流纹斑岩岩体,对于找寻W、Cu、Pb、Zn、Bi、Au、稀土、稀有和稀散元素矿产具有重要意义。     

临夏黄土记录的26万年来季风快速变化

黄土高原西部高分辨率黄土序列开展的多代用指标研究,有助于揭示轨道-亚轨道尺度上东亚冬、夏季风的变化特征及动力机制。但针对同一地质记录提取冬、夏季风多代用指标进行对比和敏感性分析的工作尚不多见,因此制约了对季风快速变化特征和机理的理解。本文利用甘肃临夏85 m黄土岩芯开展高分辨率的粒度、磁化率和元素扫描分析,发现在轨道尺度上粒度和Zr/Rb比值显示的大幅冰期-间冰期波动与深海氧同位素记录有很好的对应关系,表明东亚冬季风的波动响应于北半球高纬冰量的变化。但在千年尺度上,粒度能更敏感地响应冬季风的快速变化;Rb/Sr比值和磁化率均能很好记录轨道尺度上的东亚夏季风波动,但在亚轨道尺度上Rb/Sr的敏感性明显高于磁化率。粒度、Zr/Rb和Rb/Sr所指示的东亚季风快速变化表现出较强的岁差信号,与石笋和北纬65°夏季太阳辐射有较好的对应关系,表明东亚季风变化也受到岁差直接驱动的夏季太阳辐射变的控制。在最后两个冰期-间冰期旋回中(即末期冰期旋回和倒数第二次冰期旋回)Rb/Sr及Zr/Rb比值和粒度记录分别可以辨别出与石笋相同数量级的变暖事件,但粒度记录的暖事件明显要多于Rb/Sr及Zr/Rb比值,且这些暖事件并不能一一对应。粒度及元素比值记录显著变冷的千年尺度的Heinrich(H)事件与石笋记录的夏季风明显减弱的事件有很好的对应关系,但其发生频率明显高于海洋记录。这些指标记录的千年尺度上波动信号的不一致性主要归因指标对不同气候要素敏感性的差异。未来需要进一步开展高分辨率多代用指标敏感性分析,选取对季风快速变化的敏感指标,有助于我们理解季风快速变化的特征(如周期和幅度等)和分析季风快速变化的时空差异性。     

The Late Early Cretaceous Mo Mineralization in the South China Mo Province: Constraints from U–Pb and Re–Os Geochronology of the Lufeng Porphyry Mo Deposit

Compared to other Mo provinces, few studies focused on the South China Mo Province(SCMP), especially for Early Cretaceous Mo mineralization. The Lufeng porphyry Mo deposit in the SCMP is characterized by disseminated and veinlet-type mineralization in granite porphyry, gneiss, and rhyolite. In this study, six molybdenite samples yield a Re–Os isochron age of 108.0±1.8 Ma, which is consistent with the zircon U–Pb age of the granite porphyry(108.4±0.8 Ma). The coincidence of magmatic and hydrothermal activities indicates that Mo mineralization was associated with the intrusion of granite porphyry during the late Early Cretaceous. A compilation of U–Pb and Re–Os chronological data suggests that an extensive and intensive Mo mineralization event occurred in the SCMP during the late Early Cretaceous. The marked difference in molybdenite Re contents between Cu-bearing(85–536 ppm) and Cu-barren(1.3–59 ppm) Mo deposits of the late Early Cretaceous indicates that the ore-forming materials were derived from strong crust–mantle interactions. Together with regional petrological and geochemical data, this study suggests that late Early Cretaceous Mo mineralization in the SCMP occurred in an extensional setting associated with the roll-back of the Paleo-Pacific slab.     

基于遥感蚀变信息提取巴林格撞击坑周边铁陨石

目前地球上已经得到确认的撞击坑有190余个,其中直径小于1 km的简单撞击坑绝大部分是由铁质撞击体撞击形成的.由铁质撞击体撞击而成的撞击坑周边存在大量的铁陨石物质,这些铁陨石物质的空间分布特征对研究撞击坑的撞击过程和机理具有重要意义.铁元素的异常富集也可作为探寻地球表面疑似撞击坑的重要信息.为了获取撞击坑周围的铁陨石残...     

Late Triassic Biotite Monzogranite from the Western Litang Area,Yidun Terrane,SW China: Petrogenesis and Tectonic Implications

The Late Triassic igneous rocks in the Yidun terrane can provide vital insights into the evolution of Plaeo-Tethys in western China. We present new zircon U-Pb, whole-rock geochemistry, and Sr-Nd-Pb-Hf isotopic data for the Litang biotite monzogranites, Yidun terrane. The biotite monzogranites have a zircon U-Pb age of 206.1±1.0 Ma(MSWD=1.9,n=30), which indicates Late Triassic magmatism. The biotite monzogranites display I-type affinity, high Na_2O(3.38-3.60 wt%) contente,medii SiO_2(67.12-69.13 wt%), and low P_2 O_5 contents(0.10～0.12 wt%). They enriched in Rb,and Ba and depleted in Nb and Ta, with negative Eu anomalies(Eu/Eu*=0.74—0.81). They have evolved Sr-Nd-Pb-Hf isotopic composition, i.e.,(~(87) Sr/~(86 )Sr)i=0.714225 to 0.714763, negative ?_(Nd(t)) values of -2.0 to-2.6 with two-stage Nd model ages ranging from 1.01 to 1.05 Ga, negative ?_(Ht)(t)) values o f-3.4 to-4.1 with two-stage Hf model ages of 1.85 to1.88 Ga, suggesting a matured crustal sources. Their low Al_2O_3/TiO_2 ratios and medium Cao/Na_2O ratios, medium Mg~# and SiO_2 contents, low [molar Al_2O_3/(MgO+FeO~T)] values, and high [molar Cao/(MgO+FeO~T)] values indicate that the Litang biotite monzogranite was formed by partial melting of metabasaltic rocks. Based on the previous studies, we propose that the Litang biotite monzogranite derived from the westward subduction and closure of the Ganzi-Litang ocean during the Late Triassic-The mantle wedge-derived mafic melts provided sufficient heat for partial melting of ancient metabasalt protolith within the middle-lower crust.     

收发信机中的单片微机控制系统研制

研制了收发信机中的单片微机控制系统。采用８０３１作为ＣＰＵ，通过键盘、显示接口芯片８２７９，可以人工输入各种指令并可显示输出各种结果。控制系统能够产生收发信机所需的频率编码，通过频率合成器产生所需频率。系统具有预置频率、检错，断电保护等多种功能。     

Somaton Plus全身CT定位床不能遥控的故障维修

本文描述了西门子ＳｏｍａｔｏｍＰｌｕｓ全身ＣＴ的定位床与左支架之间通讯联络的工作原理及其故障维修,还描述了用微机电源代替ＤＣ／ＤＣ转换器的方法。