The state’s largest company Santos has lost $1.84 billion from its market capitalisation since April 20 while copper and gold miner Oz Minerals has lost $1.42 billion – a slump of 15 per cent.

The Australian share market yesterday suffered its worst session in two months, with the benchmark S&P/ASX200 index closing down 155.3 points or 2.1 per cent to 7,318 on Tuesday, while the broader All Ordinaries fell by 164.2 points, or 2.1 per cent, to 7,604.

It was the worst day for the local market since February 24, the day Russia invaded Ukraine, and follows a rout of global markets on Friday ahead of the Anzac Day long weekend when the major Wall Street indexes fell by nearly three per cent.

The sharp downturn is being blamed on concerns that lockdowns in China will reduce global demand for commodities.

Adelaide-based Oz Minerals, which operates copper and gold mines at Prominent Hill and Carrapateena in the state’s north, on Friday released its first-quarter report for the three months ending March 31.

It showed a 5 per cent fall in copper production and a 16 per cent drop in gold production coupled with a 15 per cent increase in all-in sustaining costs.

The company blamed staff shortages due to COVID-related absentees and an outback flooding event in January that disrupted supply to its South Australian mines.

The road and rail closures caused the greatest disruption at Prominent Hill, which had no site access via road for three days and limited access for 12 days.

However, it said in a statement to the market on Friday that group production and costs guidance remained on track for 2022 with a stronger operational performance expected over the balance of the year.

“The first quarter, as previously flagged, saw a softer start to the year with elevated COVID related workforce and supply challenges as we transitioned to “living with COVID” across Australia,” Oz Minerals managing director and CEO Andrew Cole said.

“Workforce absenteeism due to COVID remains elevated particularly at Prominent Hill and remains a risk to operational productivity.”

Oil and gas giant Santos last week reported record quarterly revenue from oil and gas sales, with the company cashing in on surging commodity prices and its merger with Oil Search.

The Adelaide headquartered company’s March quarter results show it generated a record $US1.91 billion ($A2.6 billion) from oil, gas and LNG sales to start the year – up 25 per cent on the last quarter of 2021.

However, the positive result has not been enough to stop its share price sliding from $9.63 to $8.21 in the past week.

Fellow SA oil and gas producer Beach Energy is down about six per cent in the past week after it announced that heavy rain had delayed work at its wells in South Australia’s Cooper Basin, contributing to a drop in oil production for the March quarter.

Santos and Oz Minerals held the No.1 and No.2 places in InDaily’s 2021 South Australian Business Index of the state’s top 100 companies while Beach Energy was No.4.

Yesterday’s drop put the ASX200 in negative territory for the year once again, after the index spent much of February and March climbing out of January’s sharp decline. It’s now down 1.7 per cent for the year.

The market was also down in the first 30 minutes of trade this morning, before recovering slightly by 11am.

“Obviously the (global) markets have been in turmoil while we’ve been on holiday, and we’re playing catch up,” said Julia Lee, chief investment officer with Burman Invest.

Lee pinned the losses on concerns that China’s zero-COVID strategy would disrupt demand for commodities. There’s been panic buying in Beijing, which is mass testing its 21 million residents, amid fears the city would be plunged into a full lockdown similar to the one in Shanghai.

The heavyweight materials sector was the worst hit, falling 5.1 per cent as the price of iron ore dropped to its lowest level since late February.

Fortescue Metals yesterday fell by 6.9 per cent to $19.76, BHP retreated 5.8 per cent to $45.66, Rio Tinto dipped 4.3 per cent to $108.76 and South32 dropped 7.9 per cent to $4.46.

The energy sector was down 4.0 per cent after oil prices fell overnight, with Santos down 4.3 per cent and Woodside Petroleum retreating 4.6 per cent after announcing production was down slightly in the March quarter.

Looking forward, Lee noted that Australian inflation figures for the March quarter would be released today, while US tech giants Microsoft and Alphabet will release quarterly earnings figures.

The Reserve Bank of Australia is also expected to increase the cash rate next week.

“All up, it looks like a pretty big end to the month,” Lee said.

 – With AAP