* Offerings come after CSRC gives final IPO approval to 10 firms
* Seven firms publish IPO prospectuses
* Three firms to list in Shanghai, four in Shenzhen
* Lull could mean $650 million in lost revenue for investment banks (Updates headline)
By Kazunori Takada and Elzio Barreto
SHANGHAI/HONG KONG, June 10 (Reuters) - The reopening of mainland China's IPO market with seven new listings announced on Tuesday is good news for investors, although analysts said brokerages could be forced to slash their earnings forecasts after a four-month hiatus in activity.
The new offerings come after the China Securities Regulatory Commission (CSRC) said late on Monday it had given final approval to 10 firms seeking to list on the Shanghai or Shenzhen stock exchanges, giving an official green light to the IPO market which had been dormant since February.
While the new activity will be a relief for investors eager to put their money to work, it underlines concerns that mainland initial public offerings will fail to live up to expectations this year and brokers could be left to rue upbeat revenue forecasts.
The seven companies which include Guangdong Ellington Electronics Technology, Shanghai Beite Technology and Shanghai Lianming Machinery, aim to raise a total of about 16 billion yuan ($2.57 billion), according to their prospectuses published on Tuesday. Three will list in Shanghai and four on the smaller Shenzhen exchange.
The CSRC last month said it was planning about 100 new listings this year, which would take the expected 2014 tally to 150 or only half the number forecast by consultants including PwC.
"Lower-than-expected IPO volumes definitely will drag down revenue and earnings for brokers this year, versus previous forecasts," Jian Li, an analyst with Macquarie Capital Securities in Hong Kong, said.
He said the revised IPO forecasts could wipe out 3 percent to 6 percent of brokerages' predicted earnings this year.
Brokerages that focus on mainland China deals include CITIC Securities , Haitong Securities and Guosen Securities.
The CSRC let around 50 companies list in January and February, marking the end of a suspension of IPO approvals that began in late 2012 but was never officially confirmed.
However, there had been no listings since then and the CSRC had not clarified the situation until it announced the 10 approvals late on Monday.
Prior to the resumption, the CSRC had said it was aiming to transform the IPO market to a registration-based system similar to that deployed in the United States, where market reception dictates how offerings are priced, when companies list and how their shares perform.
The biggest challenge for regulators will be to manage investors' expectations and pent-up demand. In a country like China, where nearly three-quarters of trading comes from retail investors, secondary market performance is also a concern.
"The market has been soft since they announced the reopening of the IPO markets. Given the softness, you want to make sure it goes well and it doesn't destabilise the index," said a Hong Kong-based investment banker, who declined to be named because of the sensitivity of the matter.
The CSI300 Index, which tracks the largest listed firms in Shanghai and Shenzhen, is down 12.5 percent so far in 2014, while the Shanghai Composite Index is down 3.9 percent.
China accounted for 40 percent of Asia ex-Japan investment banking fees in 2013, according to Thomson Reuters/Freeman Consulting Co estimates. ($1 = 6.2355 Chinese Yuan Renminbi) (Additional reporting by Shanghai Newsroom and David Lin; Editing by Stephen Coates)