ABSTRACT

The Levant basin, at the easternmost Mediterranean, formed during the opening of the Neo-Tethys at Permian to Jurassic times, as recorded by subsidence and magmatism along its SE passive margin. While the subsurface extensional structure was reconstructed in detail, the spatial and temporal distribution of igneous activity is not well known. Here we present new SIMS U-Pb dating of zircons from rifting related volcanic sequences recovered from four deep boreholes in the Levant margin of coastal Israel. The Asher volcanics, a deeply buried 2.5 km thick basaltic sequence, which accumulated within fault-bounded basin, was previously dated by K-Ar and Ar-Ar to early Jurassic times. Zircons (n=46) separated from the bottom and top of the volcanic sequence yielded 206±2 Ma and 205 to 202 Ma, respectively, indicating that Asher volcanics are of Late Triassic (Rhaetian) age. Zircon xenocrysts indicate Permian (289±2 Ma) felsic magmatism. Rifting activity in the Levant margin included several Permian-Triassic pulses of faulting and subsidence, with a prolonged magmatism-bearing rifting event at Late Carnian to Rhaetian times (~230-201 Ma). Pulsed rifting is also indicated in the conjugate, northern, margin of the southern Neo-Tethys, and the timing of subsidence and magmatic pulses well correlate to the Levant margin.

摘要

地中海最东端的黎凡特盆地形成于二叠纪至侏罗纪时期的新特提斯河开放期间，其东南被动边缘的沉降和岩浆活动记录了这一点。虽然详细重建了地下伸展结构，但火成岩活动的空间和时间分布尚不清楚。在这里，我们展示了从以色列沿海黎凡特边缘的四个深钻孔中发现的裂谷相关火山序列中锆石的新 SIMS U-Pb 测年。Asher 火山岩是一个深埋的 2.5 公里厚的玄武岩层序，堆积在断层边界盆地内，以前用 K-Ar 和 Ar-Ar 确定早侏罗世时代。从火山序列底部和顶部分离的锆石（n = 46）分别产生了206±2 Ma和205至202 Ma，表明 Asher 火山属于晚三叠世（Rhaetian）时代。锆石异晶表明二叠纪（289±2 Ma）长英质岩浆作用。黎凡特边缘的裂谷活动包括几个二叠纪-三叠纪的断层和沉降脉冲，在晚卡尼期到雷蒂时代（~230-201 Ma）有一个长时间的带有岩浆作用的裂谷事件。在新特提斯南部的共轭北部边缘也显示出脉冲裂谷，沉降和岩浆脉冲的时间与黎凡特边缘密切相关。