How to unblock an account that is held to ransom I have a blockchain account with bitcoins in but the account is held at ransom. I have to pay 2140$ to get a private key. Is there any way to report this to Blockchain. 

I did a trading agreement. The dealer put my profits into a mining account on Blockchain. To retreive my funds I need to purchase a key from the dealer to have the funds released. Hope I am making sense
I have to pay 2140$ to get a private key.

That is invariably a solid indication you were the victim of a scam.

I did a trading agreement. The dealer put my profits into a mining account on Blockchain.

This is typical of scams and nothing like what happens with honest businesses.
Blockchain don't have a type of account called &quot;mining accounts&quot;.
That isn't how Bitcoin mining actually works.
The &quot;profits&quot; are fake. Probably the criminal &quot;dealer&quot; set up a watch-only / non-spendable wallet to fool you into thinking the money shown belonged to you.

To retreive my funds I need to purchase a key from the dealer to have the funds released.

You are being cheated by someone dishonest. Keys are free. There is no such thing as a release fee in honest Bitcoin businesses.
The money you gave to the dealer was given to a criminal. Now the criminal is trying to get you to give them more money. Every time they succeed in tricking you they will invent a new reason for you to give them even more money. They will continue doing this until you either have no money left or realise that you are being tricked.


Is there any way to report this to Blockchain.

Blockchain.com and Blockchain.info are domains owned by Blockchain Luxembourg S.A. There is also a Blockchain Ltd mentioned on some of their web-pages but presumably this is a subsidiary company.
You can contact that European company through this web-page:
https://support.blockchain.com/hc/en-us/requests/new
The domain registrant is
Name:          Blockchain Admin
Organization:  Blockchain
Street:        Rue de Merl 74
City:          Luxembourg
Postal Code:   2146
Country:       LU
Phone:         +44.07476822631
Email:         email@blockchain.info

Note that the phone number looks like a UK mobile phone (cellphone), not a Luxembourg land-line.
The founder is Nicolas Cary, an American businessman.

If the wallet at Blockchain.com was created by the dealer, it is possible that Blockchain Luxembourg S.A. in Europe would not want to get involved in a dispute between you (a third party with no business relationship to them?) and their customer (the dealer). If the account was opened in your name, that might help to get them involved.
If you believe a dealer is holding your account to ransom, you should probably contact a lawyer or the police.