A crazy final week of September has already seen mergers worth $60 billion

• September has seen a flurry of activity in mergers and acquisitions with four major deals announced over the past week.

• Comcast won a bidding war for Sky, miner Randgold Resources was bought by Barrick Gold, Michael Kors picked up Versace, and Pandora was purchased by Sirius XM.

• The combined deals are worth more than $US60 billion.

• "September can always be a big month for deals," Ben Kelly, a merger arbitrage analyst at Louis Capital, told Business Insider on Tuesday.

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The final two weeks of September have seen a flurry of activity in the dealmaking space, with four major deals - and rumours of a fifth - announced in just a handful of days.

Over the weekend, the bidding war for Sky finally reached its conclusion when US broadcasting giant Comcast outbid Fox for the British company in a deal that values it at more than $US40 billion.

A rare sealed auction, in which both Comcast and Fox were required to bid for Sky's assets without knowing what the other had bid, saw Comcast outbid Fox by more than $US2 per share, offering £17.28 ($US22.71) per share to Fox's £15.67 ($US20.60).

Sky's board immediately recommended Comcast's offer to its shareholders, and the biggest takeover in European media history was complete.

"This acquisition will allow us to quickly, efficiently and meaningfully increase our customer base and expand internationally," Comcast CEO Brian Roberts said after the deal was confirmed.

The Sky-Comcast deal has been swiftly followed by three major, albeit smaller, deals. First up, Sirius XM - the New York-based digital media company focused on satellite radio - had a $US3.5 billion bid for music-streaming service Pandora accepted on Monday.

Even bigger than Sirius XM and Pandora's tie-up was news that UK-listed Randgold Resources is to be bought by Barrick Gold, creating an $US18 billion gold-mining giant, the biggest in the world, producing in excess of 200 tonnes of gold a year.

"Our industry has been criticised for its short-term focus, undisciplined growth and poor returns on invested capital," Mark Bristow, Chief Executive of Randgold said in a statement. "The merged company will be very different,"

He added: "Its goal will be to deliver sector leading returns, and in order to achieve this, we will need to take a very critical view of our asset base and how we run our business, and be prepared to make tough decisions."

The final deal of the week's mergers and acquisitions bonanza saw Michael Kors announce Tuesday that it has agreed to buy the Italian fashion house Versace in a deal with an enterprise value of $US2.1 billion.

"We are excited to have Versace as part of our family of luxury brands, and we are committed to investing in its growth," Michael Kors Chairman and CEO John Idol said in a press release.

Leaving aside the completed deals, there are also reports that ride-sharing giant Uber is ready to bid for the London-based food-delivery platform Deliveroo. Deliveroo was valued at around $US2 billion last year, and according to Bloomberg, would not be interested in selling for any price that's not "considerably higher" than its current valuation. A deal between the two companies is likely a long way off, but that it is even being discussed and reported is significant.

Why the sudden flurry of deals?

There are numerous reasons for the recent M&A boom, which also saw Coca-Cola buy Costa Coffee in late August. First up, big mergers tend to come towards the end of economic cycles. It's not entirely clear whether or not we're approaching the end of a cycle, or if the current economic and stock market boom will continue, but companies clearly think economic conditions are right for deals.

September, the final month of the third quarter, also tends to provide a solid time of year to go for a big deal.

"September can always be a big month for deals as projects that were put on hold, or were having finishing touches put on them over the Summer break get the sign-off from key decision makers coming back from their holidays," Ben Kelly, a merger arbitrage analyst at Louis Capital told Business Insider on Tuesday.

"Now we have Brexit approaching an end-game and acquirers are happy to take advantage of weak GBP to pick up assets," Kelly added with regards to deals for Sky and Randgold. Those deals saw non-UK firms buy British companies, using the weakness of the pound against the dollar to secure relatively less expensive buys.