论文部分内容阅读
报道了武当山群沉积地层碎屑锆石的U-Pb年代学特征,并对其地质意义进行了探讨.样品采自武当山群底部的杨坪组和中部双台组火山岩层之上的石英砂岩,并对切割两地层组水系中的河砂进行了采集.对碎屑锆石进行激光剥蚀-等离子体质谱原位分析,结果显示,杨坪组碎屑锆石的年龄主要为830～780Ma,少数为新元古代早期(约1.0～0.84Ga),含少量新太古代(～2.6Ga)、古元古代(～2.4Ga)和中元古代(～2.0Ga)锆石;双台组砂岩除少量的1.9～0.86Ga锆石外,主要由～755Ma的锆石(交点年龄)组成,与武当山群火山岩形成年龄相同.两件河砂样品中碎屑锆石的年龄组成分别与杨坪组和双台组砂岩锆石相似.武当山群碎屑锆石的U-Pb年代学特征表明,该地层的最早形成时代<780Ma;主要由约1.0～0.85和约830～780Ma两组碎屑锆石组成,与华南陆块西北缘汉南地区新元古代岩浆作用记录相似,指示了其物源区来自汉南或相似地区.武当山地区记录了～755和～680Ma两期具陆内拉张性质的岩浆事件,指示其经历了与汉南地区不同的构造-岩浆演化过程.因此,南秦岭地区～755Ma岩浆作用可能指示了华南陆块北缘与Rodinia超大陆之间的裂解事件,而～680Ma发生的岩浆事件标志了南秦岭与另一未知陆块之间的进一步分离.
The U-Pb chronological characteristics of detrital zircons in the sedimentary strata of the Wudangshan Group are reported and their geological significance is discussed.The samples are collected from the Yangping Formation at the bottom of the Wudang Group and the quartz above the Middle Shuangtai Formation volcanic rock Sandstone was collected and river sand was collected from the two stratigraphic water systems.Analysis of detrital zircons by laser ablation-mass spectrometry in situ showed that the age of the detrital zircons in Yangping Formation was mainly 830 ~ 780Ma , A few of them are early Neoproterozoic (about 1.0 ~ 0.84Ga), with a small amount of Neoarchean (~ 2.6Ga), Paleoproterozoic (~ 2.4Ga) and Mesoproterozoic (~ 2.0Ga) zircons; Except for a small amount of 1.9 ~ 0.86Ga zircons, mainly composed of ~755Ma zircons (intersection age), the same age as the Wudangshan group volcanic rocks.The ages of detrital zircons in the two sand samples are respectively The U-Pb chronological characteristics of the detrital zircons in the Wudangshan Group show that the earliest formation age of the strata was <780 Ma. The U-Pb chronological characteristics of the detrital zircons in the Wudangshan Group mainly consisted of about 1.0 ~ 0.85 and about 830 ~ 780 Ma, It is similar to the record of the Neoproterozoic magmatism in the Hannan area in the northwestern margin of the South China Block, indicating its source The area from Hannan or similar area recorded Wugang area ~ 755 and ~ 680Ma magmatic events in the nature of the two inland extensional, indicating that it experienced different from the Hannan region tectonic - magmatic evolution.Therefore, the South Qinling The ~ 755 Ma magmatism in the area may indicate the cleavage event between the northern margin of South China Block and the Rodinia supercontinent, whereas the magmatic event at ~ 680 Ma marks further detachment between the southern Qinling and another unknown landmass.