Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.
In the eastern part of the Central Asian Orogenic Belt(CAOB) in northeastern(NE) China, scattered outcrops of molasse deposits mark the ending of an orogeny and are crucial for understanding the evolution of the Paleo-Asian Ocean(PAO). However, the timing of tectonic events and the relationships among these strata remain controversial. To better constrain these geologic events, a comprehensive study of the detrital zircon U-Pb geochronology and geochemistry of the sandstones of the Kaishantun(KST) Formation and Kedao(KD) Group in eastern Jilin Province, NE China, was conducted. The KST Formation is traditionally considered a molasse deposit. The sandstones display low CIA, PIA and high ICV values and low Th/U and Rb/Sr ratios, which suggest that the rocks were derived from an immature intermediate-felsic igneous source and experienced a simple sedimentary recycling history with relatively weak chemical weathering. LA-ICP-MS U-Pb dating of detrital zircons from two samples of the KST Formation yields ages of 748-252 Ma, suggesting that the KST Formation was deposited between 254.5 Ma and 252 Ma in Late Permian. The zircons were mainly derived from the continental northern part of the North China Craton(NCC). In contrast, the U-Pb dating of detrital zircons from five samples of the KD Group yields ages of 2611-230 Ma, suggesting that the KD samples were deposited in the Early to Middle Triassic(ca. 248-233 Ma). The detrital zircon ages for the KD samples can be divided into groups with peaks at 2.5 Ga, 1.8 Ga, 800-1000 Ma, 500 Ma and 440-360 Ma, which suggest that the samples were derived from bidirectional provenances in the Jiamusi-Khanka Block and the NCC. These new data,combined with previously published results, suggest that at least three orogenic events occurred in central-eastern Jilin Province during the Early Permian(270-262 Ma), Early Triassic(254-248 Ma) and Middle-Late Triassic(242-227 Ma). The final closure of the PAO occurred during 242-227 Ma in the Middle-Late Triassic along the Changchun-Yanji sut
