Zinc prices slumped on Friday, retreating from the previous session's 20-month high, as inventory inflows calmed worries about potential shortages.

Most other industrial metals on the London Metal Exchange were also in the red, weighed down by the lack of robust stimulus measures in top metals consumer China and caution ahead of the U.S. presidential election.

Three-month LME zinc slid 3.6% to $3,059 a metric ton by 1000 GMT after touching its highest since early February 2023 on Thursday.

"There have been a lot of shenanigans in the zinc market this week and some of that is deflating, so that is helping to drag down the rest of the market," said Ole Hansen, head of commodity strategy at Saxo Bank in Copenhagen.

One party had taken control of up to 79% of available zinc stocks in LME warehouses, creating concern about short-term availability of metal, but that dissipated after large inflows.

LME data showed net arrivals of 10,275 tons of zinc into Singapore storage facilities over the past two days, raising total stocks to 242,425 tons .

The premium of cash LME zinc over the benchmark three-month contract jumped to $58 a ton on Wednesday, its highest since September 2022, but tumbled to $1 on Friday.

Among other metals, LME aluminium dropped 1.2% to $2,617.50 a ton, retreating from a multi-month high hit in the previous session, while copper was little changed at $9,509.

"Risk appetite is on the low side and positions are being kept relatively small because the U.S. election is too close to call and the impact could have binary outcome," Hansen said, adding that a victory for Donald Trump could bring tariff threats for China.

The most-traded December copper contract on the Shanghai Futures Exchange (SHFE) closed 0.2% down at 76,390 yuan ($10,723.51) a ton.

LME copper was on track for a fourth straight weekly decline. SHFE copper posted its third straight weekly loss.

LME nickel eased 0.7% to $16,180 a ton, lead slipped 0.8% to $2,058.50 and tin was down 0.3% at $31,050. ($1 = 7.1236 yuan)

(Reporting by Eric Onstad Additional reporting by Mai Nguyen in Hanoi Editing by David Goodman )