易门矿区的含矿层位——绿汁江组

THE ORE—BEARING STRATUM IN THE YIMEN MINING DISTRICT——LUZHIJIANG FORMATION

易门矿区主要含铜的狮山段的层位归属以及绿汁江组地层分布区的构造形态,是这一地区的老大难地质问题。本文报道狮山段岩性特征、上下接触界面、绿汁江组内的分层及其在区域上的情况,由此认为狮山段确系绿汁江组的一部分。狮山段位于绿汁江组所组成的一大海进旋回的下部,本身是一个次级海侵沉积岩系;狮山段与因民一落雪组有明显差异,不是同一层位,不是底辟或断块构造所造成。上冲于绿汁江组白云岩中的紫色层“刺穿体”是存在的,但它仅来源于狮山段而不是因民组。作为易门矿区主要含矿层的狮山段,在东川、罗茨、元江等地都找到不同程度的矿化显示,应重视在这一层位中寻找矿床。

Stratigrapliic horizon of Sishan Member, i.e, the main copperbearing sta-tum in the Yimen Mineral District, and structural pattern in the distributed area of the Luzhijiang Formation have been troubling geologists as long-stan-ding problems. Basing on the information of lithological characteristics of Si-shan Member, contact relations at its bottom and top parts, detailed subdivi-sions and regional distributing conditions of the Luzhijiang Formation obtai-ned by the author, it is affirmed in this paper that Sishan Member is a part of the Luzhijiang Formation. It locates at lower part of the transgressive cy-cle of the Luzhijiang Formation with a transgressive sedimentary subcycle it-self. There are apparrent differences between Sishan Member and the Ying-ming-Luoxue Formations. They are neither the same stratigraphic horizon nor formed by diapirism or block-fault. Purpple beds of piercement body in the Luzhijiang Formation is seen but it was not brought out from the Yinming Formation but from Sishan Member only. As a main ore-bearing layer in the Yimen District, Sishan Member with different extent shows of mineralization have been found in Dongchuan, Luoci and Yuanjiang in Central Yunnan. So, great attentions should be paid to explorating commercial copper deposits in this special layer.