The feature and forming mechanism of wood-like stone in Qingshuihe of Inner Mongolia, China

Wood grown rings,named as wood-like stone,are developed in carbonatites in Hohhot,Inner Mongolia. The wood-like stone,looking like wood grown rings,is very fine grained,smooth surface with red and pale yellow ring surroundings. Based on field investigation,the mineralogy and petro-geochemistry of the wood-like stone were studied for colorful rings,and the distribution of elements was tested by SEM. The results indicate that the wood-like stone consists of mediate to fine grained dolomite with argillaceous cement. The cement is mainly composed of sericite,K-feldspar,clay minerals and a few ilmenite,pyrite,limonite and REE minerals. Chemically,Al₂O₃,K₂O and Fe₂O₃ are richer in red ring than that in pale yellow one. Especially for the Fe element,the cps of Fe about 350 in the line scan can be used as the standard to distinguish the stripes of different colors. According to the graphical analysis of Yb/(Ca+Mg)-Yb/La,the rocks show signs of hot water activity. It is indicated that the marine carbonatite was infiltrated by hot fluids flowing through fractures after deposition. Due to the difference of temperature,Fe oxidation difference and the different content of trivalent Fe resulted in red-yellow stripe,forming the ring belt with cracks as the boundary like the tree ornamentation.