Allochemとは 意味・読み方・使い方

Allochem is a term introduced by Folk (1959) to describe the recognisable 'grains' in carbonate rocks. Any fragment from around ½mm upwards in size may be considered an allochem. Examples would include ooids, peloids, oncolites, fossil or pre-existing carbonate fragments. Fragments are still termed allochems if they have undergone chemical transformations - for example if an aragonite shell were to dissolve and be later replaced by calcite, the replacement would still be deemed an allochem.