The market for the newly approved spot bitcoin ETF has seen a robust first day of trading, with volumes on Thursday surpassing $4 billion.

The new crypto-based financial instruments from asset managers including Grayscale, BlackRock and Fidelity gained approval only yesterday from the Securities and Exchange Commission. 

With the day of trading not yet over, Grayscale's converted ETF is leading the way with more than $1.9 billion in trading volume as of 3:02 p.m. ET, according to data from Yahoo Finance compiled by The Block. BlackRock and Fidelity's ETFs ranked second and third with $942 million and $628 million in trading, respectively. 

Bloomberg's Senior ETF Analyst Eric Balchunas speculated earlier in the day that most of Grayscale's volume is likely "all …