摘要
重点研究了胶西北玲珑、大尹格庄两类金矿田的高钾－钾质脉岩，根据地质产状、岩性及与金矿化的时空 关系，该脉岩可分为三类：（１）煌斑岩；（２）安山玢岩；（３）英安玢岩类，它们分别形成于金矿化早期、同期、晚期。 元素地球化学研究表明：主要氧化物成分变异具岩浆分离结晶的一般规律，早期以辉石为主、晚期以角门石和斜长 石为主的矿物相分离结晶作用控制岩浆成分的演化。岩石富碱、高钾低钛，微量和稀土元素强烈富集大离子元素Ｂａ、 Ｓｒ、Ｒｂ和ＬＲＥＥ，亏损过渡元素Ｃｒ、Ｎｉ等，Ｒｂ相对Ｂａ和Ｓｒ亏损，Ｒｂ／Ｓｒ低，且富含挥发组分，揭示初始岩浆来源于 进入地壳深部或上地幔与地壳物质发生强烈交换的变质俯冲洋壳，弧后拉张阶段退变质过程岩石发生低程度部分 熔融。低熔程度、就位环境不同可能是导致两矿区成岩成矿作用有一定差别的主要原因。
The high potassic-potassic dike rocks in two types of goldfields of Linglong and Dayingezhuang, Northwest Jiaodong are studied. The rocks can be divided into three types, i. e. (1) lamprophyre, (2) andesiteporphyrite and (3 ) dacite porphyrite based on geological occurrence and lithology and their space-time relationship with gold mineralization. These rocks were the products of early, synchronous and late mineralization, respectively. Element geochemistry shows that variation in compositions of major oxides have general rules of magmatic fractional crystallization. The fractional crystallization of mineral phases of augite in early stage (namely in lamprophyre stage) and hornblende and plagioclase in late stage (namely from andesite-porphyrite to dacite-porphyrite stage) controlled the magma evolution. The rocks are enriched in alkali and have high K_2O content and low TiO_2 one, and are intensively enriched in large ion lithophile elements (such as Ba, Sr and Rb) and LREE, and intensively depleted in transitional elements (such as Cr and Ni). Rb is depleted compared to Sr and Ba, and Rb/Sr ratio is low. Volatile constituents are abundant. These characteristics indicate that the initial magma originated from metamorphic subduction ocean-crust that was intensively contaminated by the crust, and retrograded metamorphism processes have the features of low degree of partial melting during back-arc spreading. The different low degree of partial melting and emplacement environment may be the main causes of the different evolution of the rocks and mineralization in the two goldfields of Linglong and Dayingezhuang.
出处
《地球化学》
CAS
CSCD
北大核心
2000年第2期143-152,共10页
Geochimica
基金
国家自然科学基金!49133120
关键词
高钾-钾质脉岩
元素地球化学
金矿床
成岩作用
high potassicthe K_2O-SiO_2
potassic dike rock
element geochemistry
petrogenesis
Shandong Province
