Analysis of geochemical indices of crustal thickness based on GEOROC big data

作者：Ge Can^*; Wang FangYue; Li YongDong; Li XiaoHui; Li XiuYu; Zhou Yu Zhang; Yuan Feng; Li JianShe; Lu SanMing

来源：Acta Petrologica Sinica, 2018, 34(11): 3179-3188.

• Big data
• Crustal thickness
• Geochemical indices
• Kernel Density Estimation
• Normalized joint probability density distribution

Previous studies have shown that some geochemical indices in volcanic arc rocks are correlated with crustal thickness. The relationships between principal elements K2O, CaO and Na2O, trace elements ratios of Ce/Y, Sm/Yb, Dy/Yb, Sr/Y, La/Yb and crustal thickness have been statistically analyzed to restrict the development and variation of crustal thickness in some regions in geological history. Based on GEOROC database, the global volcanic rock data are divided into younger-crustal, younger-mantle, older-crustal and older-mantle data sets, and the normalized joint probability density distribution maps of geochemical indices and crustal thickness are obtained by Kernel Density Estimation method. The statistical results show that the distribution of K2O content in youngmantle-derived volcanic rocks has an exponential positive correlation with the present crustal thickness, the distribution of CaO content in young-mantle-derived volcanic rocks has a linear negative correlation with crustal thickness, Ce/Y, La/Yb and Sm/Yb ratios in young-crust-derived volcanic rocks have an exponential positive correlation with crustal thickness. The regression coefficients R-2 of the above five geochemical indices are all greater than 0.7, and the correlation is significant. It is believed that the thickness of the crust controls K-rich crustal materials into mantle melts and the crystallization and differentiation of calcium-rich minerals during the ascent of mantle-derived magma to the earth's surface, which results in the changes of K2O and CaO contents in volcanic rocks, and the stable regions of plagioclase, amphibole and garnet are controlled by the temperature and pressure conditions in the source region of crustal magma, resulting in the correlation between Ce/Y, La/Yb and Sm/Yb. The regression function established in this paper is based on the statistical analysis of the probability density distribution of massive data. Because of the existence of outlier data, tracing the historical variation of the crust thickness requires substantial data and statistical support. Otherwise, it is sometimes difficult to obtain reliable results.

• 出版日期2018
• 单位中国地质大学（北京）; 安徽省地质调查院; 合肥工业大学