Shares of Och-Ziff Capital Management Group tumbled on Wednesday after the hedge fund manager announced plans for a stock offering that analysts expect could dilute the company's earnings by around 7 percent. THE SPARK: The New York-based company said after markets closed on Tuesday that it plans to raise $250 million in a public offering of its shares. Och-Ziff owes about $622 million in outstanding debt on a loan due next July, and proceeds from the stock offering will be used to pay a portion of that total. It will repay the remainder of that loan with a new loan agreement that allows borrowing of up to $391 million and is due in 2016.