基性-超基性侵入岩中-大比例尺专题地质填图实践——以塔里木板块东北部坡北岩体为例

Practice of medium-large scale geological mapping for special issues in basic-ultrabasic intrusions: A case study of the Pobei intrusion in northeast Tarim Plate

目前,1∶5万地质填图规范中缺少对基性-超基性侵入岩填图方法的系统总结。以塔里木东北部坡北基性-超基性岩体为例,开展专题地质填图实践,在岩体地质、地球物理、遥感和地球化学综合调查的基础上,建立了科学问题、地质填图、矿床预测相结合的填图方法。将坡北基性-超基性岩体作为一个岩浆序列,根据岩浆性质与含矿性特征划分为2个岩浆亚序列,5个岩浆单元,分别对应不同的岩性组合。与岩浆亚序列相对应存在2类岩浆矿床,其中赋存铜镍矿化的岩相主要为橄榄岩相,含磁铁矿、钛铁矿的岩相主要与辉长岩、辉长苏长岩、辉石岩相有关。从野外踏勘、实测剖面等多个角度探讨了基性-超基性侵入岩1∶5万专题地质填图的方法,为此类工作提供了有益探索。

1∶50000 geological mapping is an important foundation geological work. However,there has been little research on geological mapping method of basic-ultrabasic intrusions. With the Pobei Cu-Ni sulfide deposit as the study case,and on the basis of practice of 1∶50000 geological mapping for special issues,geological survey by geological mapping,geological physics,remote sensing and geological chemistry,the authors designed a synthetical method combining scientific questions,geological mapping and prospecting. The Pobei basic-ultrabasic intrusion is a magma suite which can be divided into 2 sub-suites according to mineralization type and magma nature,the Cu-Ni sulfide mineralization is related to peridotite facies,whereas the magnetite and ilmentite mineralization occur in gabbro,gabbronorite and pyroxenite. The Pobei basic-ultrabasic intrusion can also be separated into 5 units corresponding to 5 types of lithofacies. The practices on 1∶50000 geological mapping are focused on field survey,measured sections,mapping routes arrangement,magma suites and units,structure mapping method,alteration mapping method,mappingprocess,map layout,prospecting and some other aspects,which provide implications for the present geological mapping for basic-ultrabasic intrusions.