Neoproterozoic dextral faulting on the Najd Fault System, Saudi Arabia, preceded sinistral faulting and escape tectonics related to closure of the Mozambique Ocean
Neoproterozoic dextral faulting on the Najd Fault System, Saudi Arabia, preceded sinistral faulting and escape tectonics related to closure of the Mozambique Ocean
复制标题
沙特阿拉伯内志德断层系的新元古代右旋断层发生在与莫桑比克洋闭合相关的左旋断层和逃逸构造之前
DOI：
--
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
M. Matsah
中科院分区：
文献类型：
--
作者：
T. Kusky;M. Matsah
新元古代Najd断裂系统横跨东非造山带2000公里，其运动史和构造意义一直备受争议。Halaban-Zarghat断裂是阿拉伯盾中最北西走向的主要Najd断裂中的东北部。新元古代吉巴拉群的几个沉积盆地被Halaban-Zarghat断裂和其他Najd断裂的线束所包围，特别是沿着断裂轨迹的右台阶。其中最大的盆地是吉芬盆地。济芬盆地的几何形态和吉巴拉群的沉积相表明，它是一个位于哈拉班-扎尔加特断裂之间的右旋拉分盆地。高级别糜棱片麻岩带位于断裂带的左侧台阶上，可能是与右旋扭压作用有关的深度剥蚀弹出构造。对济芬盆地周边和内部构造资料的分析表明，沿Halaban-Zarghat断裂的其他拉分盆地和高级糜棱岩带的位置都与沿Halaban-Zarghat断裂的早期右旋运动相一致。然而，独特的老岩石单元和济芬盆地的左行断层剖面的错动表明，Halaban-Zarghat断层和其他Najd断层的最新和最显著的错动意义是左行的。济芬盆地流纹岩基底的锆石U-Pb值为624.9±4.2 Ma，为盆地的形成和沿哈拉班-扎尔哈特断裂开始右行提供了下限。这个年龄被解释为东西方冈瓦那碰撞的最早年龄。621 Ma±7 Ma的深成岩体沿Halaban-Zarghat断裂右移10公里，表明右旋运动在621 Ma后持续了一段时间，然后转为左旋运动，两个大陆之间的增生地体被迫向北朝向一个没有海洋的面。侵入吉巴拉群的未变形长石岩脉的锆石U-Pb值为576.6±5.3Ma，为沿哈拉班-扎尔哈特断裂活动提供了上限。这可能标志着碰撞和逃逸构造结束的时间，也可能反映了位移转移到东非造山带更内部其他Najd断裂的时间。
Abstract The Neoproterozoic Najd Fault System extends for 2000km across the East African Orogen, yet its history of motion and tectonic significance are widely debated. The Halaban-Zarghat Fault is the northeastern-most of the major NW-striking Najd faults in the Arabian Shield. Several sedimentary basins of the Neoproterozoic Jibalah Group are bounded by strands of the Halaban-Zarghat Fault and other Najd faults, particularly along right steps in the fault trace. Among the largest of the basins is the Jifn. The geometry of the Jifn Basin and the sedimentary facies of Jibalah Group indicate that it is a dextral pull-apart basin between strands of the Halaban-Zarghat Fault. A zone of high-grade mylonitic gneiss is located along a left step in the fault zone and may be a deeply eroded pop-up structure related to dextral transpression. Analysis of structural data from around and within the Jifn Basin, the position of other pull-apart basins and high-grade mylonite zones along the Halaban-Zarghat Fault are all consistent with early dextral movement along the Halaban-Zarghat Fault. Offsets of distinctive older rock units and transection of the Jifn Basin by sinistral faults, however, show that the latest and most significant sense of offset on the Halaban-Zarghat Fault and other Najd faults was sinistral. A U-Pb zircon date of 624.9 ± 4.2 Ma from rhyolitic basement of the Jifn Basin gives a lower limit for the formation of the basin and initiation of dextral movement along the Halaban-Zarghat Fault. This age is interpreted as the earliest age for the collision of East and West Gondwana. A 621 ± 7 Ma pluton is offset 10 km dextrally along the Halaban-Zarghat Fault, showing that dextral motions continued for some time past 621 Ma, before switching to sinistral motions, and accreted terranes caught between the two continents were forced toward an oceanic-free face to the north. A 576.6 ± 5.3 Ma U-Pb zircon date from an undeformed felsite dyke that intrudes the Jibalah Group gives an upper time limit for movement along the Halaban-Zarghat Fault. This may mark the time that collision and escape tectonics ended, or it may reflect the time that displacements were transferred to other Najd faults in more interior parts of the East African Orogen.