【作者】 陈晶晶；

【导师】 白志民；

【作者基本信息】 中国地质大学（北京） ， 岩石矿物材料学， 2013， 博士

【摘要】 近年来,在世界各地陆续出现了多个硬玉岩产地,目前已经报道的硬玉岩产地已达十余个。随着对硬玉形成地质环境的不断深入研究以及新硬玉成因理论的出现,未来仍有可能发现更多的含硬玉岩产地。珠宝玉石业界认为,硬玉矿物含量达60%以上的含硬玉岩称之为翡翠。硬玉处于板块缝合线附近的实皆走滑断裂带,在低温高压变质作用下形成,即有揭示古板块构造特征的地学意义,同时对于进一步找寻稀有珍贵玉石也具有指示意义,对硬玉矿物的研究具有一定学术价值和商业价值,因此历来为地质学者和宝石学家所关注。目前,在我国虽还未发现翡翠矿,但在多处已发现含硬玉的含硬玉岩,本文选取我国大别山、缅甸和危地马拉典型含硬玉岩典型样品,对样品进行手标本及岩石薄片镜下观察,运用全岩分析、电子探针(EMPA)分析、X射线粉晶衍射(X-Ray)分析、红外光谱(反射法)分析、电感耦合等离子体质谱(ICP-MS)以及激光剥蚀电感耦合等离子质谱(LA-ICP-MS)等现代测试手段,首次对国内外典型含硬玉岩石产出的矿床地质特征、矿物学特征、岩石学特征、地球化学特征进行了精确测定和深入系统的研究分析,并进行对比研究,重点探讨了我国含硬玉岩的地质意义及其宝石学意义。岩石学特征表明,大别山含硬玉岩中普遍存在冠状体结构。冠状体结构总体可分为内核和反应边两部分。其中,内核为硬玉以残晶形式存在于冠状体结构内部。反应边又可细分为内带和外带,近硬玉一侧的内带为钠长石和绿闪石构成的细晶集合体,钠长石端元组分由里到外依次降低。近石英一侧的外带为亚铁钠闪石构成的退变质反应边。冠状体结构的发育,表明退变质过程中有流体的参与。矿物学特征研究表明,大别山含硬玉岩的主要组成矿物为硬玉、石英、石榴石、斜长石、金红石等组成,石英和金红石以包裹体形式赋存于硬玉和石榴石内。与缅甸和危地马拉典型含硬玉岩有较大差异性,大别山硬玉Na、Al含量相对较低,Ca、Mg、Fe含量偏高,硬玉端员分子量为Jd73.46-80.83,辉石三角图中主要投于硬玉区,仅一点投入临近硬玉区的绿辉石边界,总体上仍然属于含Ca、 Mg, Fe偏高的硬玉矿物种。而缅甸硬玉属于Na, Al含量高的较为纯净的硬玉矿物。危地马拉含硬玉岩中一部分较为纯净的硬玉,另一部分Ca含量偏高,属于硬玉化绿辉石。大别山含硬玉岩中的退变质石榴石,化学成分以铁铝榴石为主,其端元组分为Spe为0.20～1.20mol%,Pyr为17.54～27.31mol%,Gro为7.60～8.54mol%,Alm为61.14～72.51mol%。角闪石主要为碱性角闪石中的亚铁钠闪石,其次为钠钙闪石中的铝铁闪石和铁钠透闪石。钠长石端元组分Ab为86.01－100%,An为0-13.73%。地球化学特征显示了稀土微量元素分配及赋存的特征。微量元素变化规律显示矿石的成矿物质来源于原岩,表明大别山硬玉形成具有良好的继承性。大别山、缅甸、危地马拉含硬玉岩样品,受原岩化学成分的影响,原岩类型不同,稀土总量也不同。相比之下,大别山稀土总量最高,其配分曲线均呈现轻稀土富集,重稀土亏损的左高右低模式,LREE/HREE>1,但轻稀土富集的程度有所不同,具有典型的沉积岩特点。各产地δEu略有差别,大别山含硬玉岩与硬玉矿物6Eu<1。运用单斜辉石-石榴石地质温度计计算大别山含硬玉岩的温度压力为T855-1119。C,P≥2.8GPa。根据温压公式估算大别山含硬玉岩中硬玉矿物形成的温度为T1800℃,压力为P6GPa,而角闪石—斜长石形成的温度为T400-500℃,压力为P>0.2GPa。最后通过对国内外典型含碘玉岩样品的岩石学、矿物学及地球化学特征对比研究分析,结合我国成矿地质条件,探讨我国含硬玉岩未能成玉的原因,以宝石学角度分析我国含硬玉岩资源的宝石学意义。更多还原

【Abstract】 In recent years, jadeitite have been found at more than ten places in the world. As changing geological environment and deepening study, more jadeitite origins will be discovered around the world in the future. Academia considers that jadeite-bearing rocks that contained more than60%jadeitite minerals are being called jade (FeiCui), It is located in the Sagaing strike-slip fault zone, near plate sutures, formed under effects of low temperature, high pressure and metamorphism, which revealed that the geological significance of the ancient plates tectonic characteristics, the indicating significance of further searching the rare and precious jade, the academic and the commercial value of researching the jadeite minerals. Therefore, jadeites always attract the attentions by geological scholars and gemologists.So far, in China, the jade deposit has not been found yet, but the jadeitite-bearing rocks appeared in many places. This article took the typical jadeitite-bearing rocks from Dabie mountains, Myanmar and Guatemala as samples to view specimens and observe rock slices under the microscope, through whole rock analysis, electron microprobe analysis (EMPA), X-ray powder diffraction analysis, infrared spectrum (X-Ray) analysis, laser LA-ICP-MS and other modern testing means, precisely measure and systematacially analyze the characteristics of geology, mineralogy, petrology and geochemistry for domestic and foreign typical jadeitite-bearing rock deposits. After comparative researching, the article, for the first time, discussed emphatically the geological significance and the gemological significance of jadeitite-bearing rocks in China.The petrology characteristic shows that the samples from Dabie mountains exist prevalently coronal structure. It consists of two parts, the kernel and reaction margin. The kernel is the jadeite’s malcrystalline existed inside the coronal structure. Reaction margin can be subdivided into the inner zone and outer zone. The fine-grain of albite and smaragdite is closed to the inner zone. The albite’s end-members reduced from the inner zone to the outer zone. The outer zone near the quartz side is the metamorphosed reaction margin of naferon amphibole. The coronal structure indicates that fluid takes part in the process of metamorphisms. The researching on mineralogy characteristics shows that the major mineral components for the rocks from Dabie mountains are jadeite, quartz, garnet, plagioclase, rutile, etc. Quartz and rutile occur in the the jadeite and garnet as inclusion forms. The rocks in Dabie mountains are different from those in Burma and Guatemala, contain lower Na, Al, and higher Fe, belong to the high-Fe specie. The molecular weight of jadeite end-member is73.4680.83, mainly project on the jadeite area in the pyroxene triangular diagram, a small amount project on the boundary of omphacite area near the jadeite area. On the whole, the jadeitite-bearing rocks from Dabie mountains are closed to pure jadeites. The chemical composition of metamorphosed pomegranate is almandine mainly, which consists of Spe0.20-1.20, Pyr17.54～27.31, Gro7.60～8.54, and Alm61.14～72.51(mol%). The amphiboles mostly are the naferon amphibole among the alkaline amphibole, the others are the crossite and waldheimite among the calcium sodium amphibole. The albite’s end members are Ab86.01-100%and An0-13.73%.The geochemical features testify the characteristics of rare-earth trace elements. The jadeitite from Dabie mountains, Guatemala and Myanmar is under the influence of the protolith’s chemical composition. The protolith is different, so is REE. By constrast, the total REE of Dabie mountains’ is highest than any other else, its distribution curve presents the mode of LREE’s concentration (high left) and HREE’s loss (low right). LREE/HREE>1. but the enrichment degree of LREE is different. δEu in each origin is slightly different. In the jadeitite-bearing rocks and jadeite mineral from Dabie mountains,δEu>1.By using the clinopyxene-johnstonotite geologic thermometer to calculate the temperature and the pressure for the Dabie mountains’jadeitite-bearing rock, you can see the temperature is855-1119℃, the pressure is2.8GPa or higher. According to temperature-pressure formula’s estimating, the formation temperature of jadeite minerals in the Dabie mountains jadeitite-bearing rocks is about1800℃, pressure is more than6G Pa. The formation temperature and pressure of amphibole-plagioclase is separately400-500℃and over0.2GPa.Finally, under contrastive analyzing and researching on the domestic and foreign typical jadeitite-bearing rocks in the side of petrology, mineralogy and geochemistry characteristics, combined with the metallogenic geological conditions in our country, the article discussed why jades can not be formed in jadeitite-bearing rocks in China, and analyzed the gemological significance of jadeitite-bearing rock resources in China.更多还原