陕西秦岭泥盆纪盆地群构造沉积动力学研究

TECTO SEDIMENT DYNAMICS OF THE DEVONIAN BASIN GROUP IN THE QINLING OROGENIC BELT OF SHAANXI PROVINCE

陕西秦岭泥盆纪盆地群是在早泥盆世扬子板块北缘陆内裂谷沿勉略一线进一步发育成有限洋盆，而后分裂出秦岭板块，勉略洋盆与商丹洋盆的并存导致秦岭造山带出现了三个板块（扬子、华北及秦岭板块）共存的格局，由此形成了秦岭泥盆纪盆地群．在这种复杂的板块构造格局下，整个秦岭造山带出现了构造动力学成因不同的一系列盆地．在秦岭板块北缘发育了刘岭边缘盆地，在其中堆积了含火山岩的巨厚碎屑岩系（最大厚度超过１１ｋｍ）．在秦岭板块内部，由于广泛发育的伸展断裂而形成了一系列地堑和半地堑型盆地，在其中堆积了反映以陆表海为主的一套碳酸盐和碳酸盐碎屑沉积．在扬子板块与秦岭板块之间的勉略有限洋盆中发育了夹超基性至酸性火山岩、硅质岩的碳酸盐碎屑沉积．在扬子板块北缘的高川一带还发育了以细碎屑岩碳酸盐岩为主的陆表海沉积．总之。

The tecto sediment dynamics of the Devonian basins is documented based on the study of the Devonian system in the Qinling orogenic belt of Shaanxi Province. Existing evidences suggest that a group of basins, most striking in tecto sediment dynamics, developed during Devonian period in Qinling orogenic belt of Shaanxi Province. The combined evidences can be used to support that a limited ocean started to develop along Mianlue regine in early Devonian period, thus producing a complicated situation: three plates (North China, Yangtze and Qinling plates) and two limited oceans (Mianlue and Shangdan limited oceans). In the northern edge of the Qinling plate there was the Liuling marginal basin, in which a complicated assemblage with a maximum thickness of 11000 meters dominated by ditrital rock series, and pyroclast rocks was formed. The Liuling basin was a marginal basin rather than a inland sea basin and developed in a rapidly subsiding plate edge. Because of stretching faults widely developing, a series of graben and /or semi graben basins were formed within the Qinling plate. In those basins, carbonate and carbonate detrital sediments, which had epicontinental sea natures, were deposited. In the Mianlue limited ocean basin between the Yangtze and the Qinling plate the carbonate detrital sediments (more than 6000 m thick), most striking for bearing supermafic to acidic igneous and siliceous rocks, were formed. Also, along Gaochuan in the northern edge of the Yangtze plate the epicontinental sea sediment composed of fine detrital and carbonate rocks was deposited. During the Devonian period, there were a group of basins differing in tecto sediment dynamics in the Qinling orogenic belt of Shaanxi Province.