缅甸翡翠次生色的可见光吸收光谱的一阶导数谱研究

缅甸翡翠颗粒中的充填物的谱学变化特征对于次生色的形成具有重要意义。本文采用可见光吸收光谱的一阶导数谱,对缅甸次生翡翠矿的次生色部位进行了研究。研究结果显示:翡翠的红黄雾主要是由蓝雾转变而来的,绿泥石在向赤铁矿转化的过程中,使得蓝雾区的颜色由灰绿色变成黄、红色。黄雾的致色矿物主要为针铁矿,红雾的致色矿物除了针铁矿还有少量的赤铁矿。与色彩相似的烧红翡翠比较,天然红翡(红雾)的可见光吸收光谱的一阶导数谱显示出明显的针铁矿特征,而烧红的则为赤铁矿。     

黄色和红色石英质玉石的颜色成因研究

石英质玉石是由隐晶质-微显晶质石英矿物集合体组成的一种玉石,黄色和红色是石英质玉石最主要的颜色种类,近年来在珠宝市场上备受关注。前人研究结果表明,黄色石英质玉石的致色矿物颗粒非常细小,赋存于石英颗粒之间,通过一般的测试方法很难准确鉴定其种属。本文对云南龙陵、安徽霍山、广西贺州3个产地的石英质玉石进行了显微镜观察、拉曼光谱和紫外可见光吸收光谱测试,通过紫外可见光吸收光谱的一阶导数图谱,对石英质玉石的黄色和红色部位进行了研究。结果表明,黄色石英质玉石紫外可见光吸收光谱一阶导数图谱的特征峰有545~535 nm和435 nm,主要由针铁矿致色;红色石英质玉石紫外可见光吸收光谱一阶导数图谱的特征峰介于555~595nm之间,主要由赤铁矿致色;黄色和红色之间的过渡色可同时出现595~555 nm、545~535 nm和435 nm特征峰,主要由针铁矿和赤铁矿共同致色。     

海南蓬莱蓝宝石的光致发光谱学特征及意义

从光致发光光谱角度探讨了海南蓬莱蓝宝石的呈色机理.结果发现:与蓝宝石吸收光谱的500～700 nm吸收宽带相比,在500～720 nm发光波段内存在566.8 nm锐峰、600 nm左右肩峰和Cr~(3+)的694.2 nm特征峰.600 nm肩峰与其吸收峰镜像对称,566.8 nm处锐峰的产生原因复杂.600 nm肩峰可能与Fe~(2+)-Fe~(2+)离子对的电子跃迁有关;566.8 nm锐峰因532 nm激光激发Fe~(2+)-Ti~(4+)或Fe~(2+)-Fe~(3+)间的电荷迁移带,通过晶格造成Si~(4+)、Mg~(2+)等微量杂质离子敏化而产生.光致发光谱中呈现更多谱峰,能呈现离子跃迁时不同离子间发生的相互作用,为500～700 nm吸收宽带由不同致色机制的叠加给出了直接证明,是一种能全面地研究宝石矿物中致色元素能级结构的有效方法.     

“红碧石”的宝石矿物学特征

近年来,珠宝市场上出现了一种商业名称为"红碧石"的玉石,因其外观,特别是红色的体色与南红相近,常被作为南红的仿制品进行出售。本文采用常规宝石学测试、红外光谱、激光拉曼光谱、X射线粉晶衍射、紫外-可见、近红外光谱等方法,对"红碧石"样品的宝石矿物学特征进行研究。结果表明,"红碧石"整体呈现弱-中等玻璃光泽,折射率范围为1.53~1.54,摩氏硬度为6~7,与石英质玉石基本一致。红外光谱、激光拉曼光谱、X射线粉晶衍射的测试结果表明:"红碧石"的主要组成矿物为石英,次要矿物为赤铁矿和钙铁榴石。近红外光谱中5166~5200 cm~(-1)和4322 cm~(-1)附近的吸收指示了其中分子水及-OH的存在。对紫外-可见-近红外光谱进行一阶求导分析,"红碧石"样品均显示576 nm处赤铁矿的主峰,表明"红碧石"为赤铁矿致色。     

巫山县桃花赤铁矿地质特征及成因探讨

巫山县桃花赤铁矿含矿层为上泥盆统黄家蹬组,矿体呈层状-似层状分布于贺家坪背斜轴部及两翼.矿石颜色为紫红色和深紫红色,以豆状结构、鲕状结构和砂状结构为主,发育块状及条带状构造.矿石矿物以赤铁矿为主,次为菱铁矿,平均含量为90%;脉石矿物有石英、水云母、胶鳞矿、鲕绿泥石、方解石等.矿石单样品TFe为25%～56.80%,平均TFe为43.58%.矿石有害成分S质量分数低(0.05%～1.3%),P质量分数较高(0.5%～1.1%).综合赤铁矿地质特征及区域古地理分析,桃花赤铁矿为渝东-鄂西地区晚泥盆世海相沉积赤铁矿,矿床类型属"宁乡式"铁矿床.赤铁矿形成于半封闭的、氧气充足的湿热古内陆海盆近岸处,古海盆附近的古陆风化壳为威矿物源区.风化剥蚀作用形成的陆源碎屑物质经流水带入海盆.海水中的铁质胶体在充足的沙粒和适合的水动力条件下以胶体化学的方式形成赤铁矿鲕粒,赤铁矿鲕粒在强烈搅动环境中搬运和富集,最后在晚泥盆世黄家瞪期就位于近滨相至远滨相上部.     

某些矿物光谱信息及遥感意义

近年来,我们对一些常见矿物,如石英、长石、云母、伊利石、蒙脱石、阳起石、白云石、方解石、含锰菱铁矿、孔雀石、黄铁矿、磁铁矿、赤铁矿、褐铁矿、石膏和磷灰石进行了室内外光谱测试。其结果表明: 1.在可见光区范围内,它们的光谱信息是由为数不多的阳离子的电子跃迁所引起的。如Fe~(2+)离子在1100nm附近产生十分明显的强而宽的谱带。Fe~(3+)离子导致反射率曲线朝蓝波长     

桂林鸡血玉的致色机理研究

借助偏光显微镜和X射线粉晶衍射仪、电子探针、紫外-可见-近红外分光光度计等现代仪器设备,对桂林鸡血玉的显微结构、矿物组成及致色机理进行分析和探讨。桂林鸡血玉的颜色多样,包括红色、"红血黑地"、黄色、紫色和绿色5大系列。玉石主要为他形等粒变晶结构,部分区域可见变斑晶结构,主要矿物为微晶质—隐晶质石英,次要矿物主要为赤铁矿,部分玉石中还有少量的绿泥石、滑石甚至白云石等,w(SiO2_)介于94.92%到99.65%之间。不同形态的赤铁矿及其他矿物杂质是引起玉石颜色多样性的主要原因,[FeO_4]~(4-)空穴色心对可见光的选择性吸收使玉石呈现紫色。鸡血玉的红色与细尘状赤铁矿密切相关,细尘状赤铁矿越密集玉石的颜色越深,细尘状赤铁矿含水时鸡血玉的红色较为鲜艳;不同色调的黑色鸡血玉主要由鳞片状赤铁矿或集合体磁铁矿致色;黄色主要由氧化铁的含水矿物——针铁矿所引起,且随着鳞片状赤铁矿含量的增加,颜色逐渐偏向于橙黄色;不同色调的鳞片状绿泥石是玉石呈绿色的根本原因,滑石和白云石对玉石的颜色没有直接的影响,但它们的存在使玉石的光泽变暗、透明度降低。     

碧石的宝石学分类及定义界定初探

碧石属于石英质玉中一类,少有文献对其深入探讨,缺乏系统性分类以及定义界定,不能准确区别于颜色相对应的玉髓(玛瑙).为解决上述问题,本次研究应用X射线衍射、拉曼光谱、红外光谱、电子探针、紫外—可见光光谱等多种测试技术相结合方式,初步确定常见单色碧石的致色矿物,其中红碧石的致色矿物为赤铁矿,黄碧石的致色矿物为针铁矿,绿碧石的致色矿物为绿鳞石,紫碧石的致色矿物是锐钛矿和赤铁矿.结合市场实际需求,从宝石学角度以颜色特征作为碧石分类依据,将碧石从宝石学分类角度,分为红碧石、黄碧石、绿碧石、紫碧石、血滴石、风景碧石、多彩碧石等七个大类.同时,根据X射线衍射半定量分析和电子探针测试近似计算结果:红碧石测试样品中赤铁矿平均含量均不低于2.187％,凉山南红样品红色富集区域测试赤铁矿含量不高于1.767％,低于2％.因此可以考虑将2％的赤铁矿含量作为区别红碧石和南红的界限.建议以杂质矿物含量2％对碧石和相似颜色的玉髓(玛瑙)区分界定,进一步补充完善已有碧石定义.     

两种类型天然紫色翡翠的致色机理

紫色翡翠是天然翡翠中的重要品种,具有很高的经济价值,其主要有2种类型,一种呈较纯的紫色,另一种为带有蓝色色调的紫色。为探究紫色翡翠的致色机理,除采用传统的谱学及化学成分分析外,本文重点采用电子顺磁共振(EPR)、X射线光电子能谱(XPS)等,对2种类型紫色翡翠致色机理、致色元素价态等进行深入研究。结果表明,2种类型紫色翡翠均为硬玉颗粒本身呈色。紫色样品致色与Mn有关(w(Mn O)=0.0035%～0.036%),紫外可见光吸收光谱具有由Mn导致的580 nm吸收带,电子顺磁共振分析显示其主要为Mn~(3+),而并非Mn~(2+)。蓝紫色翡翠由Fe、Ti元素联合致色(w(Fe O)=0.039%～0.25%;w(Ti O_2)=0.018%～0.17%),X射线光电子能谱分析显示其主要致色离子为Fe~(2+)、Fe~(3+)和Ti~(4+),认为蓝紫色翡翠为Fe~(2+)-Ti~(4+)和Fe~(2+)-Fe~(3+)电荷转移致色,由此导致紫外可见光吸收光谱中具530和610 nm的吸收带。     

福建明溪蓝宝石的谱学特征及颜色成因

采用颜色测量、紫外-可见光谱、红外光谱等方法对福建明溪蓝宝石进行的研究表明,明溪蓝宝石颜色蓝中带黄,二色性强。紫外-可见吸收光谱中377,388和451nm吸收带较强。这些吸收带是Fe3 的d－d和Fe3 —Fe3 ,交换相合离子间的电子跃迁引起的。810nm带存在于各色蓝宝石中,强度变化较大,有时伴随有510nm吸收带。它是由Fe2 —Fe3 电荷转移形成的。570nm吸收带只出现在蓝色或绿色的蓝宝石中。结合蓝宝石红外33loom－‘吸收带与宝石颜色之间的关系,笔者将570nm吸收带归属于H、Fe、Ti构成的致色缺陷团。这一研究结果对蓝宝石呈色机理的进一步研究和宝石的合成等具有重要意义。     

沉积物中铁氧化物的定量方法及其 在白垩纪大洋红层中的应用

赤铁矿和针铁矿是自然界中最稳定的两种铁氧化物,广泛存在于地球的各个圈层。很多沉积物的颜色都是由它们引 起的,它们的形成和保存具有重要的环境指示意义。实验室中赤铁矿和针铁矿的表征和鉴定手段很多,但受其含量低、结 晶差、颗粒细小难分离等因素的困扰以及某些测试方法自身的限制,能用于铁氧化物定量分析的方法很少。文中就常用的 基于X射线衍射（XRD） 和漫反射光谱（DRS） 的铁氧化物定量方法进行了系统评价。在定性分析的基础上,采用基于 XRD的K值法获得西藏床得剖面红色页岩中赤铁矿的含量为3.81％~8.11％,采用DRS与多元线性回归相结合的方法获得北 大西洋ODP1049C孔12X岩芯段棕色层中赤铁矿和针铁矿的含量分别为0.13％~0.82％和0.22%~0.81％,橙色层中赤铁矿和 针铁矿的含量分别为0.19%~0.46％和0.29%~0.67％。与其它分析结果的比较表明,这两种定量方法在白垩纪大洋红层中的 应用是可行的。但在实际应用时,首先要通过XRD和DRS相结合来提高定性分析的准确性,然后通过综合分析铁氧化物的 预判含量范围和结晶程度来选择合适的定量方法。     

安徽巢湖凤凰山石炭系黄龙组红色灰岩矿物地球化学特征

安徽巢湖凤凰山晚石炭世黄龙组的地层主体为肉红色生物屑微晶灰岩,顶部为夹灰岩条带的泥岩。矿物学分析显 示,肉红色生物屑微晶灰岩的矿物主要为方解石,含少量针铁矿和赤铁矿。漫反射光谱分析表明,常用的古气候指标“红 度”与灰岩中铁氧化物、氢氧化物的光谱强度具显著的正相关性,而与岩石的全铁含量相关性较低,据此推测铁的氧化物 和氢氧化物是灰岩呈肉红色的重要原因。元素地球化学分析结果显示,黄龙组灰岩相对富Fe,Mn,而贫Co,Ni,在 Al-Fe-Mn,Fe-Mn-(Cu+Co+Ni)以及Cu-Pb-Zn三角判别图上,均靠近或落入热液成因区。综合地球化学特征与前人研究成 果,该文认为巢湖凤凰山黄龙组肉红色灰岩的形成很可能受到海底热液活动的影响。     

龙门山地区北川石沟里泥盆系养马坝组铁质鲕粒沉积及其环境分析

龙门山地区中泥盆统养马坝组铁质鲕粒是我国"宁乡式"鲕粒赤铁矿矿床重要铁质赋存形式。为查明龙门山地区泥盆系铁质鲕粒的沉积环境和成因机制,以甘溪石沟里剖面精细实测为基础,通过薄片鉴定和扫描电镜分析,对铁质鲕粒的沉积特征进行了详细研究。研究结果表明:龙门山地区甘溪石沟里泥盆系养马坝组铁质富集于生屑灰岩、鲕粒生屑灰岩和生屑鲕粒灰岩,呈层状或透镜状夹于粉砂质泥岩和泥岩中。铁质鲕粒是重要的铁质赋存载体,类型多样,根据鲕粒成分可将其划分为灰泥鲕粒、绿泥石鲕粒、铁化鲕粒和铁质鲕粒4种类型。龙门山地区石沟里剖面养马坝组铁质鲕粒沉积于有障壁海岸的潟湖环境中,根据鲕粒的纵横向分布特征,建立了有障壁海岸铁质鲕粒的成因分布模式,从障积滩外侧、障积滩内侧到潟湖,依次发育灰泥鲕粒、铁化鲕粒、绿泥石真鲕、绿泥石薄皮鲕和铁质鲕粒。     

Palaeomagnetic study of Archaean Banded Hematite Jasper Rocks from the Singhbhum-Orissa Craton, India

The Banded Hematite Jasper Formation within the Iron Ore Supergroup of the Singhbhum Craton in eastern India comprises fine alternating layers of jasper and specularite. It was deposited at 3000 Ma and deformed by a mobile episode at 2700 Ma. Hematite pigment (<1 μm) mixed with cryptocrystalline silica and specularite (> 10 μm) is chiefly responsible for red to brown rhythmic bands in the hematite jasper facies although thermomagnetic study also shows that minor amounts (1–2%) of magnetite are present. Palaeomagnetic study identifies a dual polarity remanence resident in hematite (D/I = 283/60°, α₉₅ = 12°) which predates deformation. Studies of the fabric of magnetic susceptibility and rock magnetic results suggest a diagenetic origin for this magnetisation with the hematite formed from oxidation of primary magnetite. The palaeopole (32°E, 24°N, dp/dm = 14/18°) records the earliest post-metamorphic magnetisation event in the Orissa Craton. A minimum apparent polar wander motion of the Orissa-Singhbhum craton of through 80° is identified during Late Archaean times (2900-2600 Ma).     

Colour origin of upper cretaceous pelagic red sediments within the Eastern Pontides, northeast Turkey

 Characteristic samples of Upper Cretaceous pelagic red sediments from different parts of the Eastern Pontides (NE Turkey) have been investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy coupled with energy dispersive analyses (SEM/EDAX). The red sediments are composed of limestone and muddy limestone, and characterized by abundant planktonic foraminifers. Hematite content ranges from 0.5 to 3.0 wt.%. Electron microscope observations suggest that the hematite pigment has a diagenetic origin. The red colour is due to presence of hematite pigment, and indicates oxidizing conditions during early diagenesis in a relatively deep marine environment. Received: 4 January 1999 / Accepted: 8 July 1999     

Constraining the colouration mechanisms of Cretaceous Oceanic Red Beds using diffuse reflectance spectroscopy

We have used diffuse reflectance spectroscopy to investigate the colouration mechanisms of hematite in Cretaceous Oceanic Red Beds (CORBs). Data for samples of CORBs from the Chuangde section in Tibet, Vispi Quarry section in Italy, and Core 12X of Ocean Drilling Program Hole 1049C in the North Atlantic were compared with calibration datasets obtained for hematite in different crystalline forms (kidney and specular hematite) and calcite matrix. Spectra for hematite in either pure form or in calibration datasets show that the centre of the reflection peak shifts to a longer wavelength and depth (D) decreases as the crystallinity of the hematite increases. Compared with specular hematite, the presence of just 0.5% of kidney hematite can cause a much deeper absorption peak and greater redness value, which indicates that kidney hematite has a higher colouration capacity than specular hematite. However, both kidney and specular hematite exhibit a good correlation between the redness value for each calibration dataset and the absorption peak depth. In all three studied sections, hematite is the main iron oxide mineral responsible for colouration. Spectral features such as absorption peak depth and peak centre reveal that hematite crystallinity gradually decreases from red shale to limestone to marl. Based on a spectral comparison of red shale in the Chuangde section before and after citrate–bicarbonate–dithionite (CBD) treatment, we found that two forms of hematite are present: a fine-grained and dispersed form, and a detrital form. The former is relatively poorly crystalline hematite, which has a much stronger colouration capacity than the detrital form. In the Vispi Quarry section and Core 12X of ODP Hole 1049C, a good correlation between the absorption peak depth of hematite and redness value indicates that the red colouration is caused by hematite of similar crystallinity in each section.     

Paleoclimatic approach to the origin of the coloring of Turonian pelagic limestones from the Vispi Quarry section (Cretaceous,central Italy)

Samples of Turonian white to light gray and red limestones from the Vispi Quarry section in central Italy have been examined by X-ray Diffractometry (XRD), Electron Probe Micro-analysis (EPMA), Electron Spin Resonance (ESR), and Ultra violet-visible-near infrared (UV-VIS-NIR) Diffuse Reflectance Spectroscopy (DRS). The ESR, EPMA and XRD results suggest that Mn²⁺ was well-incorporated into the structure of calcite during the precipitation of the limestones. Amorphous ferric oxide (most probably hematite) and the Mn²⁺-bearing calcite endowed the limestone with a red color as the major pigmentation, and the Mn²⁺-bearing calcite gave it a pink tinge. The mineral assemblage is composed mainly of detrital boehmite and quartz, which are interpreted as having been imported from the Eurasian paleo-continent into the ocean by seasonal northeasterly winds. The boehmite formed by dehydration of gibbsite as an end-product of intensive chemical weathering of Fe, Mg, and Al-bearing aluminosilicates exposed in a subtropical environment. XRD results for the residues of Cretaceous Oceanic Red Beds (CORBs) dissolved in dilute acetum differed from those from Cretaceous Oceanic White Beds (COWBs) in that they contain hematite. This suggests that no hematite was imported into the ocean during the precipitation of the white limestone, and may explain why the same detrital origin for red and white limestones resulted in different colors by suggesting that climatic variations occurred on the paleo-continent during the precipitation of these two types of limestone. The presence of boehmite and hematite suggests that, during the Late Cretaceous, central Italy lay within a subtropical climatic zone with a seasonal alternation of warm rainy winters and hot, dry summers during the formation of the CORBs, and a continuously warm climate during the formation of the COWBs. The Mn/Fe(mol) ratios in the shells of spherical carbonate assemblages (probable microfossils) suggested that the ocean was much richer in iron during the precipitation of COWBs.     

北大西洋ODP1049C孔Aptian-Albian期高频旋回大洋红层的成因:矿物学证据

北大西洋ODP171B航次1049C孔Aptian-Albian期沉积以出现大洋红层与灰色、白色沉积物高频旋回为特征。为了探讨大洋红层的成因,本文进行了矿物学、地球化学、沉积学等方面的研究。漫反射光谱、磁化率和活性铁数据表明,赤铁矿、针铁矿的出现是导致样品由白色向红色转变的矿物学原因。棕色和橙色样品中出现赤铁矿和针铁矿的特征峰,FeR/FeT平均值分别为0.23和0.24,明显区别于其他颜色的样品。磁化率与红层成良好的正相关关系,说明铁氧化物矿物含量的变化是导致磁化率变化的原因。X射线衍射结果表明,不论颜色如何,样品中均含伊利石、高岭石、蒙脱石、绿泥石等粘土矿物,其分布与样品颜色没有直接关系,很可能反映当时物源区气候稳定。ODP1049C孔岩芯沉积物出现橙色、棕色、白色、灰色等颜色的高频变化,颜色过渡接触界线清晰,说明导致红色变化的赤铁矿和针铁矿是沉积期低温氧化的产物。棕色样品中CaCO3含量最低,推测红层所对应的氧化条件是由于较低的有机质堆积速率造成的。     

PseudomonasputidaMnB1氧化分解菱锰矿的实验研究

自然界中,菱锰矿氧化形成锰的氧化物矿物是非常普遍的现象,在菱锰矿被氧化分解发生物相转变的过程中,碳酸 盐溶解和锰的氧化往往同时发生,微生物可能起着催化作用。选取锰氧化模式菌株PseudomonasputidaMnB1和广西梧州菱 锰矿,通过菱锰矿在该细菌作用下发生转变的实验,利用场发射扫描电镜、扫描透射X射线显微成像等分析方法,研究了 矿石表面形貌变化以及锰元素在细胞上的分布特征。结果表明细菌显著促进的菱锰矿的溶解,在此基础上,进一步探讨了 细菌在菱锰矿氧化过程中的贡献,本实验结果丰富了次生锰矿床的微生物成因研究。     

Iron mineralization in the Garagu Formation of Gara Mountain,Duhok Governorate,Kurdistan, NE Iraq: geochemistry,mineralogy and origin

The iron mineralization is hosted in carbonate beds of the Garagu Formation (Early Cretaceous) at Gara Mountain, Duhok Governorate, Kurdistan Region, NE Iraq. The Garagu Formation is composed of a series of limestone and siltstone beds with iron-rich beds in the middle part. The iron-rich limestones are iron-rich oolitic grainstone and bioclastic wackestone with hematite and goethite minerals. Geochemical results drawn from this study indicate that the percentage of iron in these beds reaches 19.73 %. Moreover, petrographical investigation of thin and polished sections reveals the presence of different types of fossils, indicating an open marine interior platform depositional environment. Different iron minerals, including hematite, goethite, siderite, pyrite and magnetite, were identified in the sections, and their geneses were related to syngenetic and diagenetic processes. The geochemical distribution of major and trace elements, as well as the V/Ni, V/(V+Ni), V/Cr and Sr/Ba ratios, indicates a reducing environment during the precipitation of carbonate sediments and a subsequent oxidizing condition during the concentration of iron minerals via diagenesis.