摘要
本文根据生物礁(层)在成矿过程中的作用把中国南方礁控矿床分为直接型、间接型和被动型3大类,并列举了几个典犁矿床实例进行论述和总结。研究礁控矿床除分析有利于成矿的沉积相带外,应特别注意同沉积断裂在成礁和成矿过程中的作用,以及礁岩中古油气藏对形成硫化物矿床的重要性。
Reef-controlled mineral deposits distributed extensively over southern China form an important Mississipp-type of stratabound deposit. In this paper reef-controlled mineral deposits are divided into 3 types based on the relative importance of organic reefs in the ore-forming processes. They are: 1. direct type: reef-building organisms directly absorbe and collecte oreforming elements through their own living action; 2. indirect type; the ore-forming processes take place in a reel-controlled lagoon or other depressions; 3. passive type: reef rocks only provide an ore-housing space and a favourable geochemical environment.Several typical deposits have been discussed, and the ore-formation mechanisms are summarized and discussed, It is thought that the role of reefs in the ore-forming processes should be judged according to specific circumstances. For the algal reefs, the reef rock itself can serve as an important indication for exploration. For somes stratiform deposits such as pyrite and siderite deposits, exploration work should be carried out in a reef-controlled lagoon near the oldland. For the bulk of reef-controlled lead-zinc and antimony deposits, it is necessary to make synthetic studies of relevant factors such as deposition, diagenesis and strutcure The syndepositional fault controll the distribution of different sedimentary facies in the depositional period, and then, the migration direction of thrmal brines and the position of minerali zation. The presence of a paleo-reservoir of oil and gas in organic reefs or banks not only provides a favourable geochemical environment for the percipitation of ore-forming elements, also abundant sulfur.The fundamental cause of reef-controlled mineral deposits formed in carbonate rocks in southern China is the tectonic setting of this region. For instance, in the Hercynian-Indosluian period southern China was a triangle zone affected by both the Yunnan-Qinhai-Tibet oceanic plate and the Pacific plate. The intense back-arc spreading and rifting not only produced a sedimentary framework characterized by alternating arrangement of plaforms (trenches) and basins, which were apparently controlled by basement faults as well, and also caused a great quantity of ore-forming thermal fluids to rise, thus forming local mineralized seawater. If the mineralized sea-water (plus later thermal brines) was adjacent to a suitable sedimentary or tectonic setting (e.g. reef rocks occurring in the core of an anticline), a strata?bound deposit might be formed.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1989年第1期26-35,共10页
Acta Geologica Sinica
