SEC filings dated June 30 show BlackRock with stakes in Marathon Digital Holdings and Riot Blockchain.
The bitcoin miner's stock has more than tripled this year.
The investment reflects growing institutional and individual interest in investing in crypto-related companies.
The mining company now has 6,226 bitcoins with a market value of $260.7 million.
The contract is for 30,000 Antminer S19J Pro machines, the company said in a statement.
The positive adjustment could be the beginning of a surge in hashrate in the coming year.
The publicly traded mining company generated 654.3 bitcoins in Q2, more than triple its Q1 haul.
"Marathon is committed to the core tenets of the Bitcoin community, including decentralization, inclusion, and no censorship," said the CEO.
Marathon cited Texas’ favorable regulatory climate and low energy prices, as well as environmental considerations as key factors in the decision.
The quantitative hedge fund placed heavy bets on Riot, Marathon and Canaan in early 2021.
Despite Marathon's efforts, transactions from a dark web market still made it into the block.
Thiel will take over at a time when Marathon is aggressively expanding operations.