Answer:
First came the explorers, they also brought African slaves, many who died in war and of disease in later centuries after being freed. From the mid-1800's until the mid-1900's there was a lot of immigration to Argentina because it was one of the world's wealthiest countries at that time.
While most of the immigrants were Spanish and Italian, Argentina also has Arabs, Eastern Europeans, Russians as well as Latin America's largest Jewish population and largest population of Irish descendants.
http://wander-argentina.com/jewish-argentina
http://wander-argentina.com/the-irish-in-argentina