UPDATE 1-Apart from Big 3, iron ore miners face 'existential' threat -Goldman
* Goldman cuts iron ore price forecasts for 2015-2018
* Says half of small miners' output may shut as demand peaks
* Moody's says potential of rating changes on miners 'heightened' (Adds Moody's outlook)
By Manolo Serapio Jr
SINGAPORE, April 16 (Reuters) - Up to half of iron ore output by miners outside the three mega producers in Australia and Brazil is at risk of closure with global demand set to peak at about 1.4 billion tonnes next year, Goldman Sachs said.
Production volumes among top miners - Vale, Rio Tinto and BHP Billiton - was not at risk, the bank said.
"However, the rest of the industry is now facing an existential challenge," Goldman analysts Christian Lelong and Amber Cai said in a report.
"We expect seaborne iron ore demand to peak in 2016 as the displacement of marginal Chinese iron ore production fails to offset a contraction in domestic steel consumption," they said.
Separately, Moody's Investors Service said supply reductions were dwarfed by planned increases estimated to exceed 300 million tonnes over the next several years. Continuación...