赣南富城岩体黑云母及其蚀变产物绿泥石的矿物化学研究——对铀成矿的指示意义   总被引：4，自引：1，他引：3  

赵友东  吴俊奇  凌洪飞  王洪作 《矿床地质》2016,35(1):153-168

富城花岗岩体位于赣南会昌盆地东侧,该岩体西部与橄榄玄粗岩系列火山岩接触,河草坑铀矿田就产于该花岗岩体的内外接触带中。在矿区外围花岗岩中发育大面积的蚀变带,其中的黑云母普遍蚀变为绿泥石。为了深入探讨蚀变与铀矿化的关系,文章运用电子探针技术对该蚀变带的黑云母及其蚀变产物绿泥石进行了矿物化学研究。结果表明,黑云母大部分属铁叶云母,估算出富城花岗岩岩浆的氧逸度lg(f O2)值约为-15.0~-14.3,氧逸度较低,源岩为还原性较强的岩石,有利于铀预富集于源区中;富城产铀花岗岩中黑云母的w(F)高达1.41%~2.01%,表明花岗质岩浆富F,而富F岩浆中U溶解度高,可能是富城岩体富铀的重要原因之一。黑云母被绿泥石交代后呈黑云母假象,绿泥石矿物化学分析结果表明,绿泥石以鲕绿泥石和蠕绿泥石为主,属于富铁的绿泥石,主要形成于还原环境;绿泥石的形成温度介于246~307℃之间,平均276℃。全岩U、Th含量分析结果表明,上部"红化"蚀变层中的w(U)(3.5×10-6~9.4×10-6,平均6.6×10-6)明显低于下部"绿色"蚀变层(7.7×10-6~23.1×10-6,平均13.9×10-6),而"红化"蚀变层与"绿色"蚀变层的Th含量相似,w(Th)平均值分别为35.7×10-6和36.5×10-6。矿前期的带状面型"绿色"蚀变层活化了矿物晶格中的结构铀,后期高氧逸度的流体萃取"绿色"蚀变层中已经活化了的铀而形成含铀热液,经迁移在还原带附近沉淀成矿。Th的价态(正四价)难以随这种氧化还原条件的改变而改变,因此未参与流体成矿过程。  相似文献   

江西省桃山铀矿田大府上矿床绿泥石特征及其地质意义     

李仁泽  刘成东  梁良  孔明  王冰  万建军 《岩石矿物学杂志》2016,35(2):297-305

绿泥石化是大府上铀矿床重要的成矿期蚀变类型。绿泥石的形貌特征显示该矿床绿泥石主要有2种产出形态,即沿长石、石英等矿物裂隙生长呈蠕虫状集合体产出的绿泥石和由黑云母蚀变而成的绿泥石。本文主要利用电子探针微区分析方法研究了绿泥石化学成分特征。研究结果表明,该矿床绿泥石为富铁的蠕绿泥石,形成于还原环境;绿泥石形成温度为201.48~224.20℃,平均213.65℃,属中低温热液蚀变范围;形成机制主要有"溶蚀-结晶"和"溶蚀-迁移-结晶"两种方式。绿泥石成分特征对探讨铀成矿环境与矿床评价具有重要的指示意义。  相似文献   

相山铀矿田邹家山工区含铀凝灰岩的矿化特征   总被引：1，自引：0，他引：1  

薛振华  蒋振频  董永杰  喻建发  胡荣泉  张柳贵 《铀矿地质》2004,20(2):85-90

相山铀矿田邹家山工区 5 0m中段发现含铀凝灰岩 ,化学分析结果显示 ,这种凝灰岩铀矿石中铀含量达 7 1 3 % ;该矿石中绿泥石含量较高。笔者认为 ,在相山铀矿田中 ,花岗斑岩与凝灰岩接触部位应有富铀矿体存在。  相似文献   

相山铀矿岩芯HySpex成像高光谱数据蚀变矿物提取及其地质意义     

孙雨 《地质与勘探》2015,51(1):165-174

成像高光谱遥感具有图谱合一的优势,能够根据光谱特征直接识别地物,是遥感领域的前沿方向。本文使用江西省相山铀矿田岩芯HySpex成像高光谱数据,采用基于专家知识的MTMF和波段运算方法开展了蚀变矿物填图,提取了赤铁矿、伊利石、绿泥石和方解石4种蚀变矿物,制作了铀矿岩芯高光谱蚀变矿物分布图。通过分析高光谱蚀变矿物类型、组合和分布规律,在岩芯中划分出中心蚀变带、近矿蚀变带和矿旁蚀变带,中心蚀变带蚀变矿物为赤铁矿+伊利石+绿泥石+方解石,近矿蚀变带为伊利石+方解石,矿旁蚀变带为零星分布的伊利石+方解石。其中,岩芯高光谱遥感提取出的绿泥石第二吸收峰位于2270 nm,光谱特征分析显示属于富铁绿泥石,与前人得出的与铀矿化密切相关的绿泥石主要为富铁绿泥石的结论一致。铀矿岩芯HySpex岩芯成像高光谱数据应用实践表明该数据在地质领域具有较好的应用效果和广泛前景。  相似文献   

庐江沙溪斑岩型铜金矿床绿泥石的地球化学特征及找矿指示   总被引：2，自引：2，他引：0  

何光辉  周涛发  范裕  王世伟  肖庆玲 《矿床地质》2018,37(6):1247-1259

文章在前人对岛弧环境斑岩型矿床绿泥石主微量元素找矿指示研究的基础上,以陆内环境的长江中下游成矿带中的沙溪斑岩型铜金矿床为对象,利用LA-ICP-MS技术对沙溪斑岩型铜金矿床中绿泥石进行了主微量元素研究。结果显示,绿泥石中Ti、Ba、Co、K、Pb、Sr、Fe、V/Ni靠近矿化中心的位置含量高,Mn、Mg元素远离矿化中心的位置含量高。沙溪斑岩型铜金矿床中绿泥石元素含量分布主要受温度、被交代矿物、流体pH值和氧化还原环境、围岩性质影响。受交代矿物的影响,绿泥石中的有些元素(Si、Na、Mg、K、Al)的含量高低不能直接对矿化中心进行指示,但沙溪斑岩型铜金矿床绿泥石部分元素(Ti、Ba、Co、Pb、Sr、Fe)和元素比值(V/Ni)具有指示矿化中心的作用。  相似文献   

Experimental Study of Dissolution‐Alteration of Amphibole in a Hydrothermal Environment     

LI Yongli  HUANG Fei  GAO Wenyuan  TANG Xu  REN Yaqun  MENG Lin  ZHANG Zhibin 《《地质学报》英文版》2019,93(6):1933-1946

Amphibole is a rock-forming mineral widely existing on the earth. It is easily dissolved and altered during the later stage of diagenesis and mineralization, and often forms chloritization, which is an important indicator for prospecting. To explore amphibole's dissolution process and alteration mechanism, dissolution experiments were carried out under acidic conditions using pargasite-rich amphibole as raw material, and the effects of temperature, p H, and experiment duration on amphibole alteration were investigated. Experimental samples and products were analyzed using X-ray diffractometer, field emission scanning electron microscope, electron probe micro analyzer, and transmission electron microscopy. It was found that many pores and erosion edges are produced after amphibole dissolution, and there is a clear interface between the dissolved residual portion and the parent. The dissolved residual portion remains in the amphibole phase, but as the temperature and time increase, the intensity of the diffraction peak of the phase in the product decreases, and the peak position shifts to a small angle. Many clay minerals such as chlorite and griffithite formed on the amphibole surface. In an environment with strong acidity(p H=3), the amount of chamosite increases with temperature(180°C→210°C→240°C), whereas clinochlore is only increased in a 150–210°C environment. Griffithite growth was observed in the acidic(p H=6) and low temperature(180°C) environments. Based on this analysis, large radius Cl– enters the amphibole lattice or cracks to promote dissolution. The Al-poor and Ca-and Fe-rich regions between the edge and core of the amphibole are caused by dynamic equilibrium in amphibole dissolution and alteration process, which is an essential indicator for the beginning of amphibole dissolution-alteration. Diffusion and the coupled dissolution-reprecipitation mechanism accomplishes the process of dissolution and alteration to form clay minerals. The energy of the system determined by temperature and p H is the key to controlling the rate of growth and nucleation of clay minerals. High temperature and strong acidity will dissolve more iron from amphibole, which is conducive to chlorite growth. Compared to chlorite, griffithite is more sensitive to temperature. Griffithite attaches on the amphibole surface with a star-like in a weak acid and low-temperature environment. The results of this study can provide a mineralogical basis for the analysis of hydrothermal alteration processes and the division of alteration zones.  相似文献   

Comparison of diagenetic and low-grade metamorphic evolution of chlorite in associated metapelites and metabasites: an integrated TEM and XRD study   总被引：2，自引：0，他引：2  

Árkai  M. P. Mata  Giorgetti  Peacor  & TÓth 《Journal of Metamorphic Geology》2000,18(5):531-550

Chlorite is a common sheet silicate that occurs in various lithologies over a wide grade range involving diagenesis and low‐grade metamorphism. Thus, the reaction progress of chlorite offers a unique opportunity for direct correlation of zonal classification of metasedimentary rocks based on illite crystallinity with metabasite mineral facies. To provide such correlation, chlorite crystallinity indices, apparent mean crystallite sizes and lattice strains, crystallite size distributions and compositions of chlorite from coexisting metapelites and metabasites were determined by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), analytical electron microscopy (AEM) and electron microprobe (EMP) methods. Samples were from Palaeozoic and Mesozoic formations of the Bükkium (innermost Western Carpathians, Hungary) that underwent Alpine (Cretaceous) orogenic metamorphism. Metapelites range in grade from late diagenesis to epizone, whereas metabasites vary from prehnite–pumpellyite through pumpellyite–actinolite to greenschist facies. Despite significant differences in composition, mineral assemblages and textures, reaction progress, as measured in part by chlorite crystallinity, in metapelites paralleled that in metabasites. Chlorite crystallinity and mean crystallite size increase and the proportion of mixed layers in chlorite decreases, whereas the calculated lattice strain does not change significantly with increasing metamorphic grade. Similar trends, but (especially at higher grades) significant differences, were found in mean crystallite size values using various methods for XRD line profile analyses. The increase in crystallite size with increasing grade was demonstrated also by direct TEM measurements on ion‐milled whole‐rock samples, but with a larger scatter of data at higher grades. In spite of the different kinds of mixed layering in chlorite (Mg‐rich smectitic, mostly random, local corrensite‐like units in metabasites, and Fe‐rich berthierine and dioctahedral smectite in metapelites), XRD‐calculated and TEM‐measured parameters were found to be reliable tools for measuring reaction progress and metamorphic grade of the same degree in both lithotypes.  相似文献   

The Environment Significance of Aerinite — First Discovered in the UBC Cliffs     

WANG Guanyu  WANG Hejing 《《地质学报》英文版》2020,94(1):103-113

To analyze the composition and structure of the pale blue outcrop from the UBC Cliffs and research the environmental significance of aerinite recorded in the sediments, mineral composition, bulk chemical composition and structural analyses were carried out by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), electron microprobe analysis (EMPA) and X-ray fluorescence spectra (XRF). Quartz, feldspar, mica, chlorite and aerinite as well as a small amount of amphibole, calcite, clinopyroxene, rutile, perovskite and apatite are recorded in the sediments. It is reported for the first time that the aerinite occurs in a high latitude area and in sediments paragenetic with mica and chlorite. The large span in grain size shows a typical characteristic of fluvioglacial sediments. Geochemistry characteristics (CIA, CIW, PIA, WIP and ICV) verify that there is virtually no chemical weathering. Mineralogy and geochemistry features of the UBC Cliffs sediments indicate that aerinite is accommodate to the high latitude and cold, dry climate. As the sediments show high similarity to those of their provenance, they have great significance in the identification of the forming condition and origin of the aerinite.  相似文献   

201和361铀矿床中绿泥石的特征及其形成环境研究   总被引：3，自引：0，他引：3  

张展适  华仁民  季峻峰  张彦春  郭国林  尹征平 《矿物学报》2007,27(2):161-172

绿泥石化是201和361铀矿床最重要的蚀变类型之一。本文在岩石薄片观察的基础上,采用电子探针分析技术研究了绿泥石的共生组合与形貌特征,测定了87个代表性绿泥石的化学成分,并据此划分了绿泥石的化学类型,计算了绿泥石的形成温度、n(Al)/n(Al Mg Fe)值等相关指数,讨论了绿泥石的形成机制及其与铀成矿的关系。研究表明:①岩石中绿泥石主要呈脉状、黑云母假象或团块状等产出,具有蠕虫状、叶片状等形貌特征;②绿泥石的Fe/Si图解显示201和361铀矿床中绿泥石主要为铁镁绿泥石和蠕绿泥石,少数属密绿泥石;③根据Battaglia提出的经验方程式计算了201和361铀矿床绿泥石的形成温度变化于179~276℃之间,且主要介于230~260℃之间;④绿泥石主要形成于还原环境,其主要的形成机制是溶解-沉淀和溶解-迁移-沉淀。  相似文献   

Compositional variations in mafic phyllosilicates from regional low-grade metabasites and application of the chlorite geothermometer   总被引：5，自引：0，他引：5  

R. E. BEVINS  D. ROBINSON  G. ROWBOTHAM 《Journal of Metamorphic Geology》1991,9(6):711-721

Abstract Mafic phyllosilicates in metabasites affected by low-grade regional metamorphism from Wales and eastern North Greenland show variations in their structure and chemistry. These variations are related to four mineral zones in these metabasites, which are recognized on the presence/absence of various key calc-silicate minerals and also actinolite. Zones 1 and 2 equate with the zeolite facies, zone 3 with the prehnite–pumpellyite facies (or prehnite–actinolite facies in rocks with appropriate bulk rock composition) and zone 4 with the greenschist facies. Whilst variations in Fe/(Fe + Mg) in chlorite correlate closely with Fe/(Fe + Mg) ratios in the whole-rock, other chemical variations are clearly unrelated to whole-rock compositions. Contents of Al^iv are seen to increase systematically in samples from zone 1 through to zone 4, which relate to an increase in temperature. Calibration of alteration temperatures, calculated using the chlorite geothermometer (based on Al^iv contents) developed for meta-andesites in the Los Azufres geothermal system (Mexico), against x values (an estimate of the proportion of chlorite to swelling component in the mafic phyllosilicates) shows a decrease in the swelling component in passing from zone 1 to zone 4, i.e. with an increase in temperature. Calculated temperatures compare favourably with published stability estimates for the various key calc-silicates and actinolite. These data indicate that the chlorite geothermometer, although developed for meta-andesites from a hydrothermal system, does show a correlation with temperatures estimated from calc-silicate assemblages in metabasites affected by low-grade metamorphism developed on a regional scale.  相似文献