The phrase 'comprised mainly of' is correct and usable in written English.
This phrase is typically used when you want to describe a group that is mostly made up of one particular thing. For example, "The movie trailer was comprised mainly of action scenes."
BAE also claims to have 845 "ambassadors" – comprised mainly of school governors across Britain.
The floral industry within the United States is comprised mainly of small- and medium-sized businesses.
All these and more are scheduled to address the audience, comprised mainly of arena maintenance workers and visiting school groups.
Comprised mainly of doctors and health workers providing assistance to populations in distress and victims of disasters and armed conflict.
The fully drafted policy is reviewed, or "reality-tested," by the PAG, comprised mainly of senior university administrators.
In this paper, we developed a workflow which is comprised mainly of three stages.
In a week-long party conference comprised mainly of soporific work reports and rhetoric-heavy speechifying, unbridled emotion has emerged as a counterintuitive motif.
A result is an insurance pool comprised mainly of sick individuals where premiums rival the cost of rent and where the healthy forgo coverage completely.
The disaffected £9.5m Spaniard was given his first start since November and against a team comprised mainly of youngsters and part-timers he still failed to impress.
The exposed bedrock of the zonal ground surfaces was mainly formed during the Archaean to Cenozoic, and is comprised mainly of sandstone.
Comprised mainly of depression, anxiety, and high neuroticism, psychopathology diminishes the effectiveness of many chronic pain treatments.
