Massive Sulphide Deposits Related to the Volcano‐Passive Continental Margin in the Altay Region

AbstractThe Devonian volcano‐passive continental margin in southern Altay is a significant volcanogenic massive sulphide metallogenic belt. Acidic volcanism has been dominant on the inner side of the volcano‐passive continental margin, i.e., near the old land, resulting in a Pb‐Zn metallogenic sub‐belt, in which the ore deposits are hosted by sedimentary rocks in volcanic series, as represented by the large Koktal Pb‐Zn deposits. In the central part of the margin far away from the old land, bimodal volcanic formations are well developed, forming volcanics‐hosted Cu‐Zn metallogenic sub‐belts, e.g., the large‐scale Ashele Cu‐Zn deposit. The Qiaoxiahala sub‐belt on the outer side of the margin near the ocean ridge is located at the spreading central trough, where ophiolite suites are developed. This type of deposits is rich in gold and copper, similar to the Cyprus‐type Fe‐Cu‐Au metallogenic sub‐belt in metallogenic environment (represented by the Qiaoxiahala medium‐scale Fe‐Cu‐Au deposit). From the old land to the ocean, the mineralizing age becomes younger, i.e., from Early Devonian→Early and Middle Devonian→Middle Devonian, forming a complete metallogenic zoning series on the volcano‐passive continental margin. Comparative studies show that the massive sulphide deposits distributed on the volcano‐passive continental margin are different from those formed under a plate subduction regime and oceanic ridge environment; the former have their unique features and wide distributions, representing a new type of volcanogenic massive sulphide deposits—the Altay type.