The phrase "are left mainly" is correct and usable in written English.
It can be used to indicate that something is primarily or mostly remaining or available after other elements have been considered or removed.
Example: "After the meeting, the decisions that are left mainly pertain to budget allocations."
Alternatives: "are primarily left" or "are mostly remaining".
Both are leaving mainly because family circumstances make endless trips to Beijing burdensome.
What's left mainly are anger, anxiety and a kind of flattened affection for Dad and me.
Such discussions should be left mainly between the victims and their therapists or closest confidants.
Experts think the footprints were left mainly by a group of phytophagous dinosaurs followed by a few carnivorous ones, the news agency said.
The scant outreach to American Muslims that the Bush Administration undertakes, aside from occasional religious conferences and White House iftars, is left mainly to the F.B.I.
The site was left mainly as it was after the accident, giving an uncanny and mournful appearance to the scattered debris and silent mountains.
The business of advising on restructurings has been left mainly to small boutiques like theirs because the large Wall Street investment banks have too many potential conflicts of interest.
For most of the past seven years the actual, political contours of the post-9/11 world have been left mainly to documentarians, while the realm of pop-culture fantasy has bloomed with poisonous flowers of grief, vengeance and dread.
Plantations were established both by the government and by private German corporations, but crop development was left mainly to the Togolese, assisted by agriculturists trained at a college in Nuatja (Notsé).
By 2010 only some 500 will be left, mainly in sensitive areas such as defence.Late last year the government launched an initial share offering in Vietcombank, one of five state-owned commercial banks.
