Distinctive properties of rock-forming blue quartz: inferences from a multi-analytical study of submicron mineral inclusions
Distinctive properties of rock-forming blue quartz: inferences from a multi-analytical study of submicron mineral inclusions
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造岩蓝色石英的独特性质：亚微米矿物包裹体多重分析研究的推论
作者：
W. Seifert;D. Rhede;R. Thomas;H. Förster;F. Lucassen;P. Dulski;R. Wirth
摘要本文讨论了世界范围内八个产状的成岩蓝石英的矿物学、地球化学和测温学性质。与非蓝石英相比，蓝石英含有大量的亚微米尺寸（1 μm-100 nm）和纳米尺寸（<100 nm）的包裹体。云母、钛铁矿和金红石是最丰富的亚微米级包裹体，可能是在石英和熔体之间的边界层同生沉淀形成的（包裹模型）。纳米级金红石可能是由石英结构中Ti的后生出溶作用形成的（出溶模型）。纳米颗粒夹杂物对光的瑞利散射最好地解释了蓝色的起源。蓝色石英通常富含钛（100-300 ppm），并在高温下形成（700 ℃-900 ℃）。含钛矿物的微小捕虏晶包裹体的大量和高空间密度使得使用石英中的钛温度计计算结晶温度不可靠。蓝石英的地质意义仍然不清楚。
Abstract The study discusses the mineralogical, geochemical and thermometric properties of rock-forming blue quartz from eight worldwide occurrences. Compared to non-blue quartz, blue quartz contains significant amounts of submicron-sized (1 μm-100 nm) and nanometre-sized (<100 nm) inclusions. Mica, ilmenite and rutile constitute the most abundant submicron-sized inclusions, and are formed probably by syngenetic precipitation in the boundary layer between quartz and melt (entrapment model). Nanometre-sized rutile possibly originated by epigenetic exsolution of Ti from the quartz structure (exsolution model). Rayleigh scattering of light by nano-particulate inclusions best explains the origin of the blue colour. Blue quartz is generally Ti-rich (∼100-300 ppm) and formed at high temperatures (∼700°C-900°C). The large number, and high spatial density, of tiny xenocrystic inclusions of Ti-bearing minerals make calculations of crystallization temperatures using the Ti-in-quartz thermometer unreliable. The geological significance of blue quartz remains obscure.