陕西洛南陶湾群三岔口组砾岩研究

A Study of Taowan Conglomerate in Luonan,Shaansi

陶湾群三岔口组砾岩是一套分布于华北地块南缘的水下碳酸盐岩型重力流沉积，砾岩的形成同商州铁炉子栾川断裂带早期活动性质存在因果关系。通过１∶５万区调填图发现，陶湾群三岔口组砾岩从母岩区到砾岩堆积区之间无断陷作用；沉积基底基本连续；砾岩沉积组构出现有序的横向变化规律，依次为母岩区层状白云岩（α区）、具有垂向张裂隙及流动构造的始滑区白云岩（β区）、具有节状构造的滑移区白云岩（γ区）和砾岩堆积区（δ区）。陶湾群三岔口组砾岩时代厘定为早寒武世晚期至中寒武世，这也是华北地块南缘盆地环境的主形成期，砾岩是在东秦岭洋向华北地块南缘俯冲碰撞构造环境下形成，商州铁炉子栾川断裂带为俯冲碰撞带。

Taowan conglomerates,a suite of curbonate_type gravity_flow deposits,are distributed in the southern margin of North China plate.The deposit of conglomerates is related to the protolith and the crust tectonic activity.We discover that the deposit basement without rift_faulting is basicully continuous and that the depositional fabric of conglomerates shows the ordered_tranvese change from the protolith area to the conglomerate area ,i.e. the bedded dolomite in the protolith area(α)→the dolomite with veticaltesion crack and flowed structure in the initial slip area(β)→the dolomite with segmented structure in the slip area(γ)→conglomerates area(δ).The period ot Taowan conglomerates is determined as the mid_late Cambrian Epoch,which is the principal period of paleobasining in the southern margin of North China block.The dynamic mechanism of Taowan conglomerates is directly related to the Tieluozi subduction collision zone according to the metamorphism of Kuanping Group and garnet ptt locus.Advenced study of Taowan conglomerates is very important to recogneze the coupling relationship and basin_mountain transform between Qingling orogenic belt and the southern marginal basin of North China plate.