Exhumation history and preservation of the Jiaojia giant gold deposit, Jiaodong Peninsula

The Jiaojia giant gold deposit is the largest gold deposit in China, with a total gold reserve of approximately 1200 t.Until now, the knowledge of the exhumation history of post-mineralization period is limited, in particular for the low-temperature thermochronology studies of samples below-1000 m. In this work, we combined zircon fission-track(ZFT) and apatite fission-track(AFT) dating of samples between-1100 and-2000 m to determine the post-mineralization cooling and exhumation history of the Jiaojia giant gold deposit. The ZFT ages ranged from 144.2±6.3 to 124.4±5.5 Ma, representing the cooling period and the disturbance of ore-forming fluid. The AFT ages ranged from 28.1±2.6 to 16.2±1.0 Ma, recording the exhumation and cooling processes. With reference to previous low-temperature thermochronology studies in the Jiaojia goldfield, we estimated the exhumation rate and amount of the Jiaojia giant gold deposit and reconstructed its exhumation and preservation history. The exhumation history was divided into four stages, rapid exhumation(~120–95 Ma), relatively slow exhumation(~95–50 Ma),slow exhumation(~50–30 Ma) and relatively rapid exhumation(since 30 Ma). Each stage corresponds to geological events related to the basin-mountain coupling that have occurred since the Cretaceous in the Jiaodong area, namely, a strong tectonic extension and volcanic eruption in the Jiaolai Basin, subsidence of the Jiaolai Basin and Wangshi Group molasse sedimentary,tectonic quiescence, and the Linqu Group basalt eruption of the Jiaobei uplift. Our results show that the exhumation of the Jiaojia giant gold deposit is ~5.2±1.2 km and the orebody erosion degree is relatively low, indicating huge prospecting potential deep in the Jiaojia giant gold deposit. These findings have significance and practical value for deep prospecting in the Jiaodong area.

Simultaneous determination of eight bioactive bakkenolides of Petasites tatewakianus Kitam by HPLC–UV

A high-performance liquid chromatography coupled with variable wavelength detection(HPLC–UV)was developed to evaluate the quality of Petasites tatewakianus Kitam through a simultaneous determination of eight bakkenolides:bakkenolide-L,bakkenolide-D,bakkenolide-B,bakkenolide-Ⅰa,bakkenolide-Ⅶa,bakkenolide-Ⅳa,bakkenolide-Ⅲa and homofukinolide.With a C18 analytical column,the eight analytes were efficiently separated using tetrahydrofuran–acetonitrile–water as the mobile phase in a constant program.The limits of detection and limits of quantitation of the method ranged 0.42–2.56μg/mL and 1.22–8.40μg/mL,respectively.The intra-and inter-day precisions of the method were all less than 1.83%.All the recoveries for the spiked analytes ranged 97.8%–102.4%.There were statistically significant differences among the contents of the eight bakkenolides in different parts and origins of P.tatewakianus(Po0.01).The content of total bakkenolides in rhizome was higher than that in other parts of the plant.The content of total bakkenolides in rhizome from Baishan was higher than those in other localities.The result suggested that rhizome may be the most valuable part of P.tatewakianus,and P.tatewakianus from Baishan may be the best plant resource.Our results might serve as a sound foundation for further study and application of this plant.