The inclusion of resource sharing schemes within Network Function Virtualization (NFV) ecosystems allows for optimized usage of 5G infrastructure and extended capabilities of network slicing services. In such environments, marketplaces are formed to facilitate the exchange of NFV services across administrative domains, which may, however, belong to untrusted and unreliable entities. In this work, we propose a novel zero-touch approach for cross-domain network slicing service assurance, using enterprise blockchain technologies and employing an AI-driven closed-loop automation architecture. Our approach is based on the lifecycle management of Service Level Agreements (SLAs) using smart contracts-from service negotiation to service binding, monitoring, reconfiguration and decommissioning. Our closed-loop architecture is materialized using Cloud-Native operational Data Lakes and allows to continuously monitor the status and health of exchanged services and to detect or predict SLA violations so that immediate mitigation actions are taken to ensure service continuity. The proposed approach is applied in real Content Distribution Networks scenarios within the European project 5GZORRO and our experimental results demonstrate the ability of our system to accurately predict changes in service demand and to timely respond with preventive scaling actions.