Schema.DescribeSobjectResult resultObj = Account.SobjectType.getDescribe();
Map<String , Schema.SObjectField> mapFieldList = resultObj.fields.getMap();
for(Schema.SObjectField field : mapFieldList.values())
{
Schema.DescribeFieldResult fieldResult = field.getDescribe();
if(fieldResult.isUpdateable())
{
system.debug(fieldResult.getName());
}
}