Please see the Azure Architecture Center for a best practice document on Running Apache Cassandra on Azure VMs. The document does include detail with regard to Multi-datacenter replication as it applies to replication entirely within Azure infrastructure, including performance considerations for Replication Factor. Azure Marketplace does have a Cassandra image by Bitnami that you can deploy (IaaS). What I do not have is a good example or documentation showing how to set-up and configure Replication Factor from an Azure VM to an on-premise Cassandra instance. The following blog does further discuss the available Cassandra deployment options with Azure: Planning the future for NoSQL Cassandra DB Applications on Azure.
Please let me know if you are looking for instructions on how to deploy this scenario or if you are simply looking to see if this deployment is an option? I think the most important aspect of an on-premise replication scenario is the network component. Please let me know if you have additional questions or if there is more information you require.