阿尔泰诺尔特地区地层—岩浆—构造轮廓初析

OUTLINE OF STRATIGRAPHY-MAGMA-TECTONICS IN NURT AREA OF ALTAY

新疆阿尔泰北部诺尔特地区的地质轮廓主要形成于海西期，地层主要由上泥盆统和下石炭统组成，岩石以沉积碎屑岩为主，夹火山碎屑岩和熔岩。沉积厚度较大，并且具粗砂岩、细砂岩和粉砂岩反复出现的韵律特征。诺尔特地区的火山岩为海西早、中期形成，早期形成岩屑、晶屑凝灰岩和英安岩，海西中期形成石英斑岩和凝灰岩，前者以中性为主，后者则偏酸性；在构造分区图上投点表明，前者落在Ａ区，属非造山带火山岩，后者落在Ｂ区，属造山带及岛弧火山岩区；稀土配分型式表明，海西早期火山岩的铕异常明显，海西中期火山岩的铕异常不明显。诺尔特地区花岗岩属海西晚期产物，数量不多，通过ＡＲ─ＳｉＯ２图、Ｋ—Ｎａ─Ｃａ图、ＡＣＦ图等图解的分析表明，它们属碱性岩浆成因的Ｓ型花岗岩，稀土元素配分型式显示花岗岩分界明显，但曲线平缓，分异不彻底。诺尔特地区地质构造演化的基本轮廓：早期是一种类似坳拉谷的环境；中期逐步闭合并抬升；晚期裂谷完全闭合，整个地区露出水面接受剥蚀。

The geological outline in the Nurt area of Altay of Xinjiang was formed in Hercynian stage.Upper Devonian and Lower Carboniferous are the major strata, which mainly consists of sedimentary elastics with interbedded volcaniclastics and lavas, and rhythm of coarse sandstones, fine sandstones and siltstones,of great thickness in depth. The volcanics in the Nurt area was formed at early and middle Hercyuian, consisting of crystal-lithic tuffs and dacites of mainly intermediate content at earlier stage, and quartz porphyries and tuffs of more acidic content at later stage. The earlier-formed volcanics belongs to non-orogenic type and falls into area A by projection in diagram of tectonic divisions, while the later-formed volcanics belongs to orogenic and island arc type, and falls into area B. The REE partition pattern shows the former owns obvious Eu anomaly , but tile latter not. The granites in the Nurt area, not in a large-scale, were formed at late Hercynian stage, and belongs to S-type of alkali aromatic origin according to the analyses of diagrams of ARSiO2, K-Na-Ca and ACF etc. The REE partition pattern shows the granites are obviously differentiated but not completely since the curve is flat. The tectonics demonstrates an aulacogen-like environment at earlier stage, gradual closing and uplift of rift valley at middle stage, and complete closing and uplift of rift valley at later stope.