西藏改则县多龙矿集区发现岩墙岭蛇绿岩残片

西藏班公湖-怒江缝合带北缘多龙矿集区是青藏高原新近发现的具有超大型远景的、典型的富金斑岩型铜矿集区,其成岩成矿地质背景是解决班公湖-怒江洋构造演化的关键问题之一。近年来的区域地质调查研究发现,多龙矿集区南侧出露岩墙岭蛇绿岩残片,应该是班公湖-怒江蛇绿岩带的重要组成部分。岩墙岭蛇绿岩主要由席状岩墙群、枕状玄武岩和硅质岩组成,整体呈棱形或透镜体状断续分布于侏罗系复理石沉积内,构成典型的网结状构造。糜棱岩普遍发育在岩墙岭蛇绿岩和围岩的接触部位。综合前人研究成果,初步认为多龙矿集区早白垩世成岩成矿作用应该形成于增生楔之上伸展拉张的构造环境。岩墙岭蛇绿岩的发现和确定进一步约束了多龙矿集区成岩成矿地质背景,同时为班公湖-怒江缝合带的延伸及其构造演化的研究提供了新的线索。     

Metallogeny of the Baiyangping Lead‐Zinc Polymetallic Ore Concentration Area,Northern Lanping Basin of Yunnan Province,China

The Lanping Basin in the Nujiang‐Lancangjiang‐Jinshajiang (the Sanjiang) area of northeastern margin of the Tibetan Plateau is an important part of eastern Tethyan metallogenic domain. This basin hosts a number of large unique sediment‐hosted Pb‐Zn polymetallic deposits or ore districts, such as the Baiyangping ore concentration area which is one of the representative ore district. The Baiyangping ore concentration area can be divided into the east and west ore belts, which were formed in a folded tectogene of the India‐Asia continental collisional setting and was controlled by a large reverse fault. Field observations reveal that the Mesozoic and Cenozoic sedimentary strata were outcropped in the mining area, and that the orebodies are obviously controlled by faults and hosted in sandstone and carbonate rocks. However, the ore‐forming elements in the east ore belt are mainly Pb‐Zn‐Sr‐Ag, while Pb‐Zn‐Ag‐Cu‐Co elements are dominant in the west ore belt. Comparative analysis of the C‐O‐Sr‐S‐Pb isotopic compositions suggest that both ore belts had a homogeneous carbon source, and the carbon in hydrothermal calcite is derived from the dissolution of carbonate rock strata; the ore‐forming fluids were originated from formation water and precipitate water, which belonged to basin brine fluid system; sulfur was from organic thermal chemical sulfate reduction and biological sulfate reduction; the metal mineralization material was from sedimentary strata and basement, but the difference of the material source of the basement and the strata and the superimposed mineralization of the west ore belt resulted in the difference of metallogenic elements between the eastern and western metallogenic belts. The Pb‐Zn mineralization age of both ore belts was contemporary and formed in the same metallogenetic event. Both thrust formed at the same time and occurred at the Early Oligocene, which is consistent with the age constrained by field geological relationship.     

重度石漠化区不同土地利用方式下土壤养分特征

本文以云南省蒙自市西北勒乡碧色寨村石漠化土地为研究对象,基于主成分分析法（PCA）研究岩溶石漠化区不同土地利用方式下的土壤养分特征。结果表明:（1）研究区土壤各养分指标变异系数介于0.14~1.76,不同土地利用方式下,土壤养分状况有较大差异;（2）研究区土壤12项养分指标可归结为3个主成分,所提供的信息占全部信息的90.69%,其中PC1主要包含了全磷、有效磷、速效钾和有效锰,PC2主要综合了有机碳、全氮、全钙和有效锌,有效铁对PC3具有较大的贡献。（3）对不同用地类型土壤养分的主成分得分进行排序,由大到小依次为火龙果地>林地>封育草地>玉米地,表明植树造林及火龙果种植等方式能有效改善石漠化区的土壤养分状况。建议对样区的石漠化治理应以封山育土为前提,以生态恢复为目的,通过种植火龙果与修复林地改善样区土壤状况,逐步形成生态环境与社会经济协调发展的石漠化综合治理体系。      

Early Cretaceous K-rich rhyolites from the Duolong Cu–Au deposit,southern Qiangtang,China: evidence for crustal growth

We report new zircon U–Pb age, Hf isotopic, and major and trace element data for rhyolites from the Duolong Ore Concentration Area of the Southern Qiangtang Terrane. Building on previous studies, we constrain the tectonic setting and propose a model to explain the geodynamics and crustal growth during regional magmatism in the Early Cretaceous. The analysed rhyolites yield laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages of 115 and 118 Ma. The rocks are K-rich (K₂O = 6.66–9.93 wt.%; K₂O/Na₂O = 8.2–19.7 wt.%), alkaline and peraluminous (A/CNK = 1.02–1.46), and are characterized by high SiO₂ contents (72.8–78.8 wt.%) similar to highly fractionated I-type granites. Fractionation of Fe–Ti oxides, plagioclase, hornblende, Ti-bearing phases, apatite, monazite, allanite and zircon contributed to the variations in major and trace element chemistry. High K₂O contents are likely due to partial melting of the continental crust. The samples have positive zircon εHf(t) values ranging from +7.1 to +11.2. These features, together with young zircon Hf crustal model ages of 489–721 Ma, indicate that the K-rich rhyolites were derived from juvenile lower crust with an input of a mantle-derived component. We suggest that the Early Cretaceous K-rich rhyolites formed in a continental arc setting during northward subduction of Bangong Co–Nujiang oceanic lithosphere. Basaltic magma underplating was responsible for vertical crustal growth, triggered by slab roll-back in the Duolong Ore Concentration Area in the Early Cretaceous.     

甘肃南部大水金矿集区找矿标志及找矿潜力分析

甘肃南部大水金矿集区金资源丰富,已累计探明金资源量150余吨。本文通过地面高精度磁测、水系沉积物测量、土壤测量以及大比例尺地质剖面、构造蚀变填图等多元勘探手段,总结归纳大水金矿集区成矿特征与规律,并得到以下找矿信息:区内二叠系、三叠系碳酸盐岩与金矿关系密切,地层对金矿起赋存定位作用;断裂构造对成矿起主导地位;岩浆活动与金矿成矿作用之间存在成因联系;蚀变对金矿化起控制作用;土壤测量所圈定的金异常与矿体对应程度高,土壤次生晕是该区找金的直接标志;中酸性侵入体能引起磁异常,而金成矿与中酸性岩体有密切时空关系。根据上述找矿标志,在格尔托金矿矿区新增金资源量10t;在格尔珂金矿深部不仅控制已知矿体的延深,并且发现数条厚大盲矿体,新增金资源量3t。     

江西兴国均村-高兴地区氟水文地球化学特征研究

氟广泛分布于地下水且与人体健康相关,世界上许多国家和地区均存在高氟水。本文以江西省均村-高兴地区为例,结合区域水文地质调查成果开展地下水中氟水文地球化学特征研究,探讨研究区地下水中F-的分布特征与来源。对研究区4个地下水系统中的442个地下水样品的F-、Ca²⁺、HCO_3^-浓度及pH值、TDS等进行分析,研究认为各地下水系统地下水中的F-浓度与Ca²⁺浓度、HCO_3^-浓度、pH值、TDS正相关,含氟矿物的溶解是地下水中氟的主要来源,较强烈的地下水交替条件及弱酸性的地下水特征是导致地下水中氟浓度低的重要原因。     

关键元素与生命健康:中国耕地缺硒吗?

地球上的生命和非生命都是由自然界已发现的92种化学元素组成的,通过全国土壤地球化学基准值与人体血液元素含量对比研究,发现血液中40~50种化学元素平均值与土壤地球化学基准值的分布高度一致,表明这些关键元素与生命息息相关。近年大家持续关注的硒(Se)元素是人体必需的微量元素,缺乏会产生健康风险,但摄入过量也会导致中毒,因此被称为健康窗口元素。过去研究认为,中国耕地缺硒是造成健康危害的原因之一。本文通过对全国3 382个网格化点位土壤采样,获得Se的地球化学基准值和空间分布数据,发现中国贫硒国土面积,按照世界卫生组织推荐值(0.1 mg/kg)和中国规范(0.125 mg/kg)计算,分别占21.1%和31.6%;适宜区(0.125~0.40 mg/kg)面积大约555万km²,占国土面积约57.1%;富硒区(>0.40 mg/kg)面积达110万km²,占国土面积约11.2%。贫硒国土主要分布在青藏高原和内蒙古局部地区,而中国9大平原的粮食主产区耕地总体上不缺硒,其中珠江三角洲平原、广西平原、成都平原、长江中下游平原是富硒区(>0.40 mg/kg),华北平原、东北平原、三江平原、关中平原是硒边缘区-适量区(0.125~0.40 mg/kg),只有河套平原是缺硒区(<0.125 mg/kg)。根据覆盖全国的网格化土壤采样分析结果,发现低硒带呈不连续的片状分布于内蒙古东部至青藏高原一带,与传统认为“低硒带分布于东北三省至西南云贵高原”不完全一致。硒的空间分布模式主要受地质背景、岩石类型、土壤类型和自然地理景观控制。     

CMIP5多模式集合对江苏省气候变化模拟评估及情景预估

利用中国气象局所属的2 400余个台站观测资料制作的分辨率为0.25°×0.25°数据集中的气温、降水量资料评估了CMIP5中17个模式对于1961—2004年江苏省气温和降水量空间分布特征的模拟能力,筛选出了5个对江苏省气候特征模拟较好的模式。之后基于5个优选模式集合平均的结果预估了3种典型浓度路径(Representative Concentration Pathways,RCPs)下江苏省2006—2100年的气温和降水量变化趋势。结果表明:(1)全球耦合气候模式对江苏省的气温和降水量空间分布特征具有一定的模拟能力,并且模式集合平均的气温和降水量与观测资料的空间相关系数分别为0.85和0.93;(2)在低浓度路径(RCP2.6)、中浓度路径(RCP4.5)和高浓度路径(RCP8.5)3种温室气体排放情景下,江苏省2006—2100年的地表温度均呈现明显的增温趋势,并且苏北的增温幅度要高于苏南;(3)3种温室气体排放情景下,江苏省未来百年降水量均呈现出北方增多南方减少的趋势;(4)未来百年江苏省降水量随气温变化的趋势并不稳定,RCP2.6和RCP4.5情景下降水量随气温的升高而增加,而RCP8.5情景下降水量随气温的增加而减少。