华北石炭纪含铝建造沉积学研究

作者在铝土矿研究中发现了许多新的显微成因结构类型。依据这些标志提出了一个铝土岩的沉积学成因分类。并划分了主要微环境的铝土岩微相类型。作者鉴定出四种铝土质沉积序列。综合上述研究,作者建立了华北石炭纪钼土矿沉积模式。在这一模式中风暴浊流对铝土矿形成富集起着特殊重要的作用。

STUDY ON THE SEDIMENTOLOGY OF THE CARBONIFEROUS ALLITE-BEARING FORMATION (SEQUENCE) OF NORTH CHINA

In this study the authors have discovered many characteristic textures and structures of bauxite as shown in Fig. 1 and P1. I, 1-6. Based on these criteria a sedimen-tologic classification of bauxite (Table 1) is proposed as follows:I. Primary bauxite:1. Autochthonous bauxite: Autocoated bauxite and algal-bound bauxite;2. Allobauxite: granular bauxite and muddy bauxite. II. Secondary bauxite:1. Shelly bauxite;2. Honeycomby bauxite.The following is the main bauxite microfacies (MF):’AWCI’ MF: coarse-grained bauxite deposits transported by current-wave generation (Fig.2);’AWCC’ MF: coarse coated-grained bauxite transported by current-wave generation (Fig.1-1);’AUCC’ MF: Auto-weathered coated-grained bauxite former in eluvial-crust environment;’RTC’ MF: resedimentary coarse-grained bauxite deposits transported by storm-turbidity flow.Four types of sedimentary sequence have been recognized by the authors: 1. current-channel sequence (Fig 3); 2. turbidity sequence (Fig. 4); 3. tidal flat sequence (Fig. 5); 4. coastal-submarine sequence (Fig. 6). Main ore deposits of bauxite are in the 1, 2 and 3 sequences.To sum up, the authors suggest a schematic sedimentological model for the formation of the Carboniferous bauxite of North China (Fig. 7), in which the process of storm-tubidity flow has played an important role in the aceumulation of bauxite deposits.The evidence of storm activity in the sedimentary sequence is as follows: 1) The presence of hummocky stratification in limestones, 2) The presence of swaley cross stratification in sandstones, 3) the characteristic turbidity pattern normal probability cumulative curve in RT-bauxite, and 4) the re-sedimentary textures and structures found in bauxite (Figs. 1 B, C. G. H. I and J).