新一代天气雷达回波强度异常分析与处理方法

根据新一代天气雷达回波强度在线定标修正原理,结合新一代天气雷达(CINRAD/要SA和SB)回波强度接收和定标及发射功率在线测量信号流程,对雷达回波强度出现的异常现象进行了详细分类和分析,总结提出了新一代天气雷达回波强度偏强、偏弱、回波面积减少等异常问题的分析思路和处理方法,列举了有效解决雷达回波强度异常故障的案例.结果表明:采用这种方法能提高处理新一代天气雷达回波强度异常故障的时效性和可靠性.     

内蒙古乌兰浩特市索伦镇中二叠统哲斯组海相暗色泥岩有机地球化学特征

在对内蒙古索伦地区中二叠统哲斯组岩性特征、沉积环境和暗色泥岩油气地球化学特征研究的基础上,总结了烃源岩的有机质丰度、干酪根类型和热演化的特征.暗色泥岩累积厚度达640m.总有机碳(TOC)的含量在0.38%～1.78%之间,TOC大于0.6%的样品占98%.有机质类型为Ⅱ～Ⅲ型.Tmax在354～548℃之间,Ro平均值3.24%,表明干酪根演化进入高-过成熟阶段.研究中还发现,S1+S2(<0.2mg/g)和IH(<16mg/g·c)都很低.造成上述结果的原因是,烃源岩已经经历过极高的热演化和排烃过程,排烃发生在晚二叠世和早白垩世晚期.     

甘肃合作市阿什加金矿床特征及找矿前景分析

阿什加金矿位于西秦岭夏河—合作断裂带北部,区内成矿条件优越。该矿是近年来新发现的一金矿床,处于岗岔至阿什加矿集区,对其进行分析研究,可为区内综合分析和地质勘查工作提供参考与对比。矿区现已探获8条金矿体,平均金品位3.03×10^-6。矿体受地层岩性、构造和岩浆岩控制,北西向层间构造为成矿热液的运移提供了通道和沉淀的场所,并控制矿体的产出和规模,在其变化段易形成工业矿体。褐铁矿、黄铁矿、辉锑矿和毒砂与金矿化关系密切,金主要以包裹金形式赋存于其中,金矿化的富集与蚀变的强度和硫化物含量呈正相关关系。通过总结分析矿床基本地质特征,并结合岗岔—阿什加矿集区成矿特征,认为在矿区深边部仍具较好的找矿前景。     

西藏列廷冈铁多金属矿侵入岩锆石U_Pb定年、Hf同位素组成及其地质意义

西藏列廷冈铁多金属矿床位于冈底斯-念青唐古拉岩浆弧北缘,是冈底斯北缘Pb_Zn_Ag_Cu_Fe多金属成矿带上典型的铁多金属矿床,与成矿关系最为密切的岩体为花岗闪长岩和花岗斑岩。采用锆石LA_ICP_MS对花岗闪长岩和花岗斑岩进行了定年,结果显示花岗闪长岩的成岩年龄为58.69±0.68 Ma,花岗斑岩成岩年龄为60.69±0.98 Ma。与加拉普铁多金属矿、沙让钼矿、亚贵拉铅锌银矿等冈底斯-念青唐古拉岩浆弧上其它矿床的对比分析表明,这一系列矿床受印度-欧亚大陆碰撞过程中地幔的岩浆底侵作用影响,形成于印度-亚洲大陆碰撞早期。列廷冈锆石的Lu-Hf测试结果显示岩体的εHf(t)值为-3.01~3.0,Hf二阶段模式年龄742~1 322 Ma,表明岩浆具有壳幔混源的特点。结合列廷冈的目前勘探情况,认为在区域的铁多金属矿中,深部的Cu、Pb、Zn矿产将是今后勘查方向。     

钚在地下水中的存在形式及影响因素分析

运用PHREEQC模拟软件对西北某区钻孔地下水中钚的存在形式进行了模拟计算,结果显示,钚以Pu(Ⅳ)价态的Pu(CO3)2(OH)22-为主,占82.28%;其次为Pu(Ⅴ)价态的PuO2+、PuO2CO3-和Pu(Ⅵ)价态的PuO2(CO3)22-,分别占8.52%、7.82%和1.17%。同时研究了pH值和pE值对钚在地下水中存在形式的影响。     

镎在地下水中存在形态的模拟计算

镎是放射性废物中的关键核素,研究镎在地下水中的存在形态及影响因素,可为今后研究镎在地质介质中的迁移行为及迁移规律,提供必要的资料支持和指导。这里运用PHREEQC模拟软件计算了镎在西北某区钻孔地下水中的存在形态,并讨论了水温、pH值以及pe值对镎存在形态的影响。结论是镎的存在形态受pH值及pe值的影响较大,但温度对镎存在形态的影响较小。     

极低放射性废物地质处置中的几个问题

极低放废物是国际上近年来新提出的一种放射性废物,目前尚未形成公认的定义和处置方案。针对地质填埋中几个关键科学问题进行了初步探讨,涉及到的内容主要包括区域地壳的稳定性、基础地质条件、水文地质条件、地球化学条件、地质灾害、安全评价等方面,最后提出了今后几个重要的研究方向。     

Geology and Hydrothermal Alteration of the Duobuza Gold‐Rich Porphyry Copper District in the Bangongco Metallogenetic Belt,Northwestern Tibet

The Duobuza gold‐rich porphyry copper district is located in the Bangongco metallogenetic belt in the Bangongco‐Nujiang suture zone south of the Qiangtang terrane. Two main gold‐rich porphyry copper deposits (Duobuza and Bolong) and an occurrence (135 Line) were discovered in the district. The porphyry‐type mineralization is associated with three Early Cretaceous ore‐bearing granodiorite porphyries at Duobuza, 135 Line and Bolong, and is hosted by volcanic and sedimentary rocks of the Middle Jurassic Yanshiping Formation and intermediate‐acidic volcanic rocks of the Early Cretaceous Meiriqie Group. Simultaneous emplacement and isometric distribution of three ore‐forming porphyries is explained as multi‐centered mineralization generated from the same magma chamber. Intense hydrothermal alteration occurs in the porphyries and at the contact zone with wall rocks. Four main hypogene alteration zones are distinguished at Duobuza. Early‐stage alteration is dominated by potassic alteration with extensive secondary biotite, K‐feldspar and magnetite. The alteration zone includes dense magnetite and quartz‐magnetite veinlets, in which Cu‐Fe‐bearing sulfides are present. Propylitic alteration occurs in the host basic volcanic rocks. Extensive chloritization‐silicification with quartz‐chalcopyrite or quartz‐molybdenite veinlets superimposes on the potassic alteration. Final‐stage argillic alteration overlaps on all the earlier alteration. This alteration stage is characterized by destruction of feldspar to form illite, dickite and kaolinite, with accompanying veinlets of quartz + chalcopyrite + pyrite and quartz + pyrite assemblages. Cu coexists with Au, which indicates their simultaneous precipitation. Mass balance calculations show that ore‐forming elements are strongly enriched during the above‐mentioned three alteration stages.     

Mineralogical Characteristics and Short-wave Infrared Spectra of Chlorite as Indicators of Hydrothermal Centers: A Case Study of the Giant Porphyry Copper-Molybdenum Deposit at Qulong, Tibet

The Qulong deposit in Tibet is one of the largest porphyry copper-molybdenum deposits in China. We used short-wave infrared (SWIR) spectroscopy to examine the spectral characteristics of the extensively developed chlorite in this deposit. X-ray diffraction and electron microprobe analyses were used for phase identification and to obtain the chemical composition, ion substitution relationships, and formation environment of the chlorite. SWIR spectral parameters were applied to detect the hydrothermal centers. The results indicate that the wavelength of the absorption feature for Qulong chlorite Fe-OH (Pos2250) range from 2240 to 2268.4 nm; the chlorite substitution relationships are dominated by Mg-Fe substitution at the octahedral sites together with AlⅣ-Si substitution at the tetrahedral sites; the chlorite formation temperatures range within the medium-low temperature hydrothermal alteration range from 164 to 281°C, with an average value of 264°C; the wavelength of the chlorite peak position for Fe-OH (2250 nm) absorption and its chemical composition are positively correlated with AlⅥ, Fe + AlⅥ, Fe/(Fe + Mg), Fe, and Fe + AlⅣ but negatively correlated with Mg and Mg/(Fe + Mg); and the wavelength associated with the chlorite Fe-OH (2250 nm) absorption feature is positively correlated with the temperature at which the chlorite formed. These correlations indicate that more Fe and AlⅥ ions and fewer Mg ions at the octahedral sites of chlorite lead to a longer the wavelength of the chlorite Fe-OH (2250 nm) absorption feature and a higher chlorite formation temperature. The wavelength of the Qulong chlorite Fe-OH (2250 nm) absorption feature (>2252 nm) can thus serve as an exploration indicator to guide the detection of hydrothermal centers in porphyry copper deposits. The results of the study indicate that the mineralogical and SWIR spectral characteristics of chlorite are significant indicators for locating hydrothermal centers within porphyry deposits.     

西藏马攸木金矿成矿背景与成矿阶段

基于地层、构造、地球化学、同位素年龄等证据,认为马攸木金矿形成于雅江洋盆的消减俯冲-碰撞以来直至现代的地质构造环境,其成矿可分为3个成矿阶段,即古近纪俯冲碰撞期成矿阶段、中新世碰撞后伸展期成矿阶段和晚上新世以来的碰撞后快速隆升成矿阶段。