川东侏罗山式褶皱构造带的物理模拟研究

Physical Modeling of the Jura-Type Folds in Eastern Sichuan

川东地区发育一系列NE走向的侏罗山式褶皱构造,按照褶皱的组合形态,自东向西发育隔槽式褶皱和隔档式褶皱,齐岳山断裂是二者的分界线。本文采取物理模拟手段对川东侏罗山式褶皱形成的控制因素进行实验研究,选取硅树脂模拟滑脱层,石英砂和微玻璃珠模拟沉积盖层,改变盖层与基底之间摩擦力、盖层的物性、滑脱层的埋藏深度等因素。模拟实验研究表明,滑脱层的深度和盖层性质是川东侏罗山式褶皱形成的主要控制因素。齐岳山断裂以东地区主要是下寒武统膏页岩充当滑脱层,滑脱层埋深较大,地表构造形态表现为隔槽式褶皱;齐岳山断裂以西地区,下二叠统泥质灰岩充当滑脱层,埋深较浅,盖层表现为隔档式褶皱。微玻璃珠是模拟侏罗山式褶皱较好的实验材料,推测川东薄皮构造带形成时候以塑形变形为主。

Jura-type folds are well-developed in the Eastern Sichuan fold-thrust belt.This belt extends from Huayingshan Fault to Dayin Fault and is separated into two areas with different structural styles by the Qirue Fault.Ejective folds occur in the west of the Qirue Fault , while trough-like folds in the east.To better understand the controlling factors of the ejective and trough-like folds in this area , six sand box experiments with varying main controlling factors were designed to simulate the evolution of the thrustfold belt.Loose dry quartz sand and glass micro-beads were used to construct the overlying sediments. Silicone putty on basement represents the detachment layer.Different basal highs of silicone putty simulate different depth of detachment layers.The experimental results show that the basal detachment depth plays an important role in controlling deformation styles of the Jura-type folds.Deeper detachment layers result in trough-like folds , while shallower detachment layers lead to ejective folds.These experiments also suggest that micro-glass beads are appropriate to simulate overlying sediments of the Jura-type folds.We infer from these experiments that the skinned structure of Eastern Sichuan were dominated by ductile deformation.