Geochemical characteristics,cooling history and mineralization significance of Zhangtiantang pluton in South Jiangxi Province,P.R. China

The zircon SHRIMP dating of the Zhangtiantang granite gave an age of 159±7 Ma.,which shows that the granite was produced at the early Late Jurassic.The Ar-Ar plateau ages of biotite and K-feldspar from the Zhangtiantang pluton are 153.2±1.1 Ma and 135.8±1.2 Ma,respectively.The Ar-Ar anti-isochrone ages of biotite and K-feldspar are 152.5±1.7Ma and 135.4±2.7Ma,respectively.The ages represent the isotopic closure ages of minerals in the pluton.The Zhangtiantang granites are regarded as peraluminous crust-derived type granites to possess the typical geochemical characteristics of calc-alkaline rocks on continental margin,with enriched Si,K,Al(average value of A/CNK as 1.18),HREE,Rb,U,and Th,heavily depleted V,Cr,Co,Ni,Ti,Nb-Ta,Zr,Sr,P,and Ba,strongly negative Eu and common corundum normative(average value of C as 1.84).The εNd(t) values of the Zhangtiantang granite are-5.84 to-7.79,and t2DM values are 1.69 to 1.83 Ga,which indicates partial melting of continental-crust metamorphic sedimentary rocks during the Middle Proterozoic.The cooling history of the Zhangtiantang granitic pluton indicates that the cooling velocity of pluton was faster(about 67℃ /Ma) from zircon(158 Ma) to biotite(152 Ma),and was slower(about12℃ /Ma) from biotite(152.5 Ma) to K-feldspar(135.8 Ma).It can be deduced that the temporal gap(about 10 Ma) between the granite formmation and W-Sn mineralization in South China may be related to ordinary magma-hydrothermal processes by the variational cooling curve of the pluton.The Zhangtiantang pluton was formed in a compressive setting,with differentiation evolution and mineralization occurring in a relative relaxation setting.

深度学习在口罩人脸检测领域的应用进展

新型冠状病毒主要以呼吸道飞沫的方式传播,正确佩戴口罩可以有效预防病毒传染,但口罩导致的部分遮挡问题使得人脸检测和识别算法的准确率大幅降低。为此,文章对深度学习基础理论及基于SSD,YOLO,RetinaNet等模型的人脸检测算法进行分析,探讨深度学习在该领域的应用进展,为进一步设计更有效口罩人脸算法提供方向性的指引。

海水铜离子污染对喜盐草生长及抗氧化酶活性的影响

为探讨海水中铜离子(Cu^(2+))污染对喜盐草(Halophila ovalis)生长的影响,通过室内种植喜盐草,然后添加不同质量浓度重金属Cu^(2+),培养2周后测定了喜盐草生物量、色素含量、可溶性蛋白含量、3种抗氧化酶活性及植物组织内的铜含量。结果显示:不同质量浓度的Cu^(2+)对植株的生物量和相对生长速率影响显著(P<0.05),对色素含量的影响不显著(P>0.05);可溶性蛋白含量随着Cu^(2+)质量浓度的增加而增加;超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性随着Cu^(2+)质量浓度的增加而降低;喜盐草地上部分对重金属铜富集量高于地下部分,且随着海水中Cu^(2+)含量的增加富集量增加。研究表明,当海水重金属Cu^(2+)质量浓度超过0.1 mg/L时,喜盐草生长速率、抗氧化酶活性显著降低,可导致海草床退化;重金属铜主要富集于地上部分,可导致喜盐草快速落叶,影响海草床的生态功能。