几内亚福雷卡里亚YML铁矿区构造变形特征及控矿规律研究

Study on structural deformation and ore-controlling rules in YML iron deposit in Forécariah Prefecture, Guinea

Yemsaliya(简称YML)铁矿区位于几内亚福雷卡里亚省东南部,Rokelide造山带北部,其太古宙地体中赋存有丰富的条带状铁矿(BIF)。研究区内岩矿层由一系列复式褶皱构成,北西走向,主体是复式向斜形态;区内发育三种面理,分别为早期的褶皱层理S_0、后生面理S_1和后期的褶劈理S_2。根据数据分析,结合构造变形特征、岩性特征、构造规模及发育程度可将区内的褶皱构造变形和面理置换过程划分为前期和后期。从前期到后期,褶皱构造样式从明显的紧闭复合同斜型向开阔的复合型过渡,岩石也从塑性向脆性过渡。区内发生的面理置换类型为,前期S_1置换S_0;后期S_2置换S_1和S_0,前期的置换作用最强。在深入剖析YML铁矿区构造变形特征的基础上,总结出一套褶皱构造变形和面理置换对铁矿床的控制规律,对同类型矿床的找矿工作具有借鉴意义。

YML iron deposit is located in the north of Rokelide orogenic belt,belongs to the Forécariah Prefecture,Guinea.This area develops abundant banded iron formation(BIF)of Archean greenstone belt.By the field survey,we gets many occurrence data which indicates that this stratum are constituted by a series of compound folds with NW strike.The main body of the stratum appears compound synclines.This area develops three types of foliations:early fold bedding(S0),epigenetic foliation(S1)and late foliation(S2).According to the analysis results of the rock occurrence data,structural deformation characteristics,lithologic characteristics,structure scale and structure develop level in this area,we divided the fold deformation and foliation replacement into early stage and late stage.From early stage to late stage,the fold structural styles experienced transition from tight compound homocline to open compound fold,and the rocks have also been transformed from plasticity to brittleness.The type of foliation replacement including that S1 replace S0 in the early stage and S2 replace S1 and S0 in the late stage,the early stage is much intensive.Based on the study on the structural deformation characteristics including fold deformation and foliation replacement,we summarized a series of ore-controlling rules,which have guiding significance to prospect in the same type of iron ore deposit.