Research In Motion’s investment arm, BlackBerry Partners Fund, has expanded its venture capital financing overseas with the launch of a $100 million fund focused on mobile investment opportunities in China.

The new fund was formed in conjunction with China Broadband Capital Partners and will invest exclusively in China’s growing mobile ecosystem.

Research In Motion (RIM) co-CEO Jim Balsillie said the fund will “help fuel substantial innovation and commercial success within the mobile ecosystem in China.”

The Chinese market has hundreds of millions of wireless subscribers and dwarfs that of the U.S. China Mobile, the country’s largest operator, has upwards of 544 million subscribers, more than three times the number of AT&T and Verizon Wireless’ combined customer base.

The country is still in the process of deploying 3G services with the TD-SCDMA standard and presents a huge, untapped market for handset manufacturers. Kevin Talbot, co-managing partner of BlackBerry Partners Fund, said the launch of the new fund positioned the investment group to take advantage of investment opportunities in “one of the fastest growing mobile computing markets in the world.”

The creation of the fund, called BlackBerry Partners Fund China,is expected to close on August 31, 2010.