水晶内金红石包裹体成因研究OA

Rutile is one of the common solid inclusions in quartz crystals.In addition to existing as a single mineral inclusion,there is also a special growth phenomenon of the intergrowth of rutile and hematite forming"rutile star".This study investigates the crystallographic orientation relationship and formation mechanism of rutile inclusions within quartz crystals through various analytical techniques including optical microscopy,Raman spectroscopy,X-ray diffraction(XRD),scanning electron microscopy(SEM)and crystallographic structure analysis.The results indicate that the rutile inclusions in quartz crystal samples are either protogenetic or syngenetic inclusions.Micro-scopic observations revealed two distinct morphological types of rutile:one is the oriented arrangement of rutile with irregular bamboo-joint-like fractures,and the other is the elongated prismatic rutile growing with hematite as the core,forming a"rutile star"with an approximate 60° angle.Since the {100} or {010} plane nets of rutile are structurally similar to the {001} plane net of hematite,the {100} or {010} plane of rutile can be joined and grow with the {001} plane of hematite.There are two possible crystallographic orientation relationships for the intergrowth of rutile and hematite:the c-axis of rutile is parallel to the＜210＞direction of hematite,and the＜101＞direction of rutile is parallel to the＜210＞direction of hematite.The formation of"rutile star"inclusions originates from the parent hematite-ilmenite solid solution.As the temperature decreases,the solid solution decomposes into ilmenite and hematite.The Fe2+in ilmenite is oxidized to Fe3+,resulting in the formation of hematite and rutile.The rutile nucleates perpendicular to the {001} planes of hematite and grows progressively along {001} planes of hematite,ultimately forming"rutile stars"with hematite as the core and rutile crystals intersecting at 60°.