Geo-clustering using SQL Server 2012 Enterprise with AlwaysOn We are trying to take our current SQL 2012 Enterprise edition 3 node cluster (OS 2012) and add a 4th node to the cluster that will be at another location.  And everything I find is telling me to use SAN replication to handle the data movement from local cluster to geo-cluster node.  WHy?  Doesn't AlwaysOn handle that data movement piece?  Any insight would be appreciated.  Thanks.
You are essentially trying to create a DR node. Availability Groups in SQL Server 2012 and above supports this scenario. Your node has to be part of the same windows cluster. The SQL Server instance on the secondary site can be configured as a secondary replica for the existing availability group. Once that is done, you will be able to sync changes from primary replica to the secondary replica. Your scenario is documented here: https://msdn.microsoft.com/library/hh781257.aspx