论文部分内容阅读
准噶尔盆地基底性质历年来一直存在争议,而花岗岩地球化学特征对下地壳性质具有指示意义.研究发现,红山岩体的岩石类型主要为碱长花岗岩,具有高SiO2、低Al2O3、偏碱性、准铝质、轻重稀土分馏相对明显且富集轻稀土、明显的Eu异常、富集Rb、Th、K等大离子亲石元素及Zr、Hf等高场强元素而强烈亏损Sr、Ba、P、Ti等元素的A型花岗岩特征,形成于后碰撞的张性环境中.SIMS和LA-ICP-MS测试获得的岩体侵位年龄分别为315.7±2.4 Ma(MSWD=0.82)和317.8±3.8 Ma(MSWD=2.8),指示该岩体为晚石炭世早期的产物,与西准噶尔后碰撞岩浆活动的时限一致.红山碱长花岗岩的结晶温度为680~860℃,Lu-Hf、Sr-Nd同位素特征共同表明西准噶尔的基底是由亏损地幔演化而来的年轻地壳物质组成.
The basement characteristics of Junggar Basin have been controversial over the years, and the geochemical features of granites are indicative of the characteristics of the lower crust. The study shows that the rock types of Hongshan Rock are mainly alkali-long granite, with high SiO2, low Al2O3, Quasi-aluminum, light and heavy rare earth fractionation is relatively obvious and enriched in light rare earths, Eu anomalies, enriched Rb, Th, K and other large ion lithophile elements and Zr, Hf and other high field strength elements and a strong loss of Sr, Ba, P , Ti and other elements formed in the post-collision tension environment.The emplacement age of rock mass obtained by SIMS and LA-ICP-MS were 315.7 ± 2.4 Ma (MSWD = 0.82) and 317.8 ± 3.8 Ma (MSWD = 2.8), indicating that the rock mass is the product of the early Late Carboniferous and consistent with the post-collision magmatism of West Junggar.The crystallization temperature of Hongshan alkali-long granite is 680 ~ 860 ℃, and Lu-Hf, Sr- The Nd isotopic characteristics together suggest that the basement of West Junggar is composed of young crustal material that evolved from the depleted mantle.