A volatile week ended with the ASX 200 sinking on the back of concerns about the progress of the global economic recovery.

Surging COVID cases amid the latest variants also dampened investor confidence, but a number of popular shares still delivered weekly gains. The ASX 200 ended the week 0.5% lower than last Friday, on 7,273.30 points.

Which shares excelled?

Sydney Airport (ASX: SYD) was among the biggest stories this week when the company announced that it had received a takeover offer from a consortium of investors led by IFM Investors. The bid, valuing Sydney Airport at approximately $22 billion or $8.25 per share, appeared to receive a somewhat frosty reception from management, based on their initial comments. However, news also emerged throughout the week that a rival bid from Macquarie, as part of its own consortium, could be in the works. By the end of the trading week, shares in SYD were up more than 30%.

Easing restrictions in China steelmaking hub of Tangshan helped buoy sentiment and prices in the iron ore market. This was positive for a number of companies in the sector, including Grange Resources (ASX: GRR), which also benefitted as the Australian dollar touched its lowest levels year-to-date. The tailwinds even sparked a boom of confidence among management, with the company Managing Director and CEO Honglin Zhao buying on-market to add to his large stake.A production update from West African Resources (ASX: WAF) sparked a rally in the gold explorer shares. It announced gold production of 63,610 ounces across the June quarter, with the company M1 South underground project reporting a quarterly increase in gold production of 116%.Dairy duo A2 Milk (ASX: A2M) and Synlait Milk (ASX: SM1) both had a stellar week as some positive momentum continues to build for the sector. The two stocks have effectively been rising in tandem with one another since mid-May, and A2 Milk also confirmed it has received approval from the NZ Overseas Investment Office for its proposed acquisition of a 75% interest in Mataura Valley Milk.Investment management company Challenger (ASX: CGF) was another of this week best-performing shares, with the stock gaining 12% at one stage after announcing a new major shareholder on its books. Leading retirement services firm Athene, along with its strategic partner Apollo Global Management, bought a 15% stake in Challenger, increasing their existing stake to 18%.Two other popular names in the Selfwealth community that put in a strong showing over the week, despite weakness heading into the weekend, were Zip Co (ASX: Z1P) and Lynas Rare Earths (ASX: LYC), even though neither business released any price-sensitive news to the market.

Which shares dragged on the market?

This week worst-performing names from the mid-to-large cap sectors came from an assortment of backgrounds, with a number moving despite announcing no news. This included Polynovo (ASX: PNV), Piedmont Lithium (ASX: PLL), Nine Entertainment Co (ASX: NEC), Clinuvel Pharmaceuticals (ASX: CUV) and Nanosonics (ASX: NAN).

Despite a positive earnings guidance from Australian Ethical Investment (ASX: AEF), where it touted a 51.1% return after all fees for its Emerging Companies Fund, the stock was pummelled. One explanation for the drop may be tied to an increasing level of short interest in the stock over recent months, and the stock lofty valuation of late.

Shares in Tabcorp (ASX: TAH) fell after the company demerger and spin-off plans for its wagering division disappointed shareholders. The business had fielded offers from prospective suitors with regards to a sale of the division, however, Tabcorp management have shied away from that proposition, even if leaving the door open to revised bids.Logistics business Qube Holdings (ASX: QUB) has seen its share price sink to its lowest level in nearly eight weeks. Earlier in the week, the company announced it would sell warehouse and property assets worth nearly $1.7 billion. However, that was somewhat overshadowed by news that costs associated with the automation of its Moorebank IMAX Terminal would still be footed by Qube.Magellan Financial Group (ASX: MFG) found itself on the back foot this week after publishing its latest Funds Under Management (FUM) report. The results showed net outflows of $351 million during the June quarter, split between retail and institutional channels.Finally, it was a dour week for Selfwealth community favourites Imugene (ASX: IMU), Brainchip (ASX: BRN) and Appen (ASX: APX), which all shed around 9-10% of their respective market caps.

We'll be back next week with another Weekly ASX Trading Wrap Up - until then, have a great week!