Characteristics and Metallogenic Potential of Skarn copper-lead-zinc Polymetallic Deposits in Central Eastern Gangdese
佘宏全(Hong-Quan She)；丰成友(Cheng-You Feng)；张德全(De-Quan Zhang)；潘桂棠(Gui-Tang Pan)；李光明(Guang-Ming Li)
地质学 ； 矽卡岩矿床 ； 斑岩矿床 ； 铜－铅－锌多金属矿床 ； 矿床特征 ； 成矿作用 ； 冈底斯 ； 西藏 ； geology ； skarn deposit ； porphyry deposit ； copper-lead-zinc polymetallic deposit ； geological characteristics of ore deposit ； metallogeny ； Gangdese ； Tibet
|Volume or Term/Year and Month of Publication||
24卷5期（2005 / 10 / 01）
508 - 520
The skam copper-lead-zinc polymetallic deposits are distributed in an EW-striking metallogenic belt some 450 km long and 90 km wide. The metallogenic belt can be divided into three sub-behs, i.e., Lhasa-Xietongmen in the western part of Gandese, Jiama-Linzhou in the northeast and Gongga-Zalang- Zhedang in the south- ern part along the Brahmaputra River, with most of the ore deposits located in Jiama-Linzhou sub-belt. The ore deposits show apparent regional zonal distribution. There exist various kinds of polymetallic deposits, such as iron-copper, copper-lead-zinc-(gold-silver), copper-molybdenum-lead-zinc, copper-gold deposits, and independent copper, lead, zinc and iron deposits. The ore-bearing strata consist mainly of Jurassic-Cretaceous marine carbonate strata and carbonate-bearing marine volcanic-detrital strata. The ore-controlling stocks are dominated by small granitic stocks or porphyries belonging to calcic alkaline N high-K-calcic alkaline series. Orebodies mainly occur in stock-contact zones and tectonic zones beside stocks. The main ore-controlling structures include interlaminar tectonic zones, stock-contact zones and fracture zones. The ore formation shows notable multistage mineralization characteristics, the copper, lead and zinc sulfides must have been precipitated mainly at the retrograde skam stage, and the favorable temperatures for ore precipitation range from 160 to 380℃. Sulfur, hydrogen and oxygen isotope studies indicate that the ore-forming fluids and materials were mainly derived from magmatic fluids. The Re-Os isochronic ages of ore deposits in Jiama-Linzhou region are concentrated in a narrow range of 15-17Ma, coincident with the stretching period in the crust after the formation of the main collision belt in Tibet plateau. This implies that the formation of skam deposits was related to the partial melting at depth and the fluid concentration resulting from the stretching after Indian-Asia plate collision. The skam deposits and the porphyry copper deposits in this region have similar magrnatic-tectonic and metallogenic geodynamic conditions. These two types of ore deposits were formed in the same period and belong to the same metallogenic series. The skarn deposits are characterized by polymetallic association, high grade, great size and high economic value. Central Gangdese has favorable geological and geochemical environments for the formation of skarn deposits. It is concluded that Jima-Linzhou basin along Leqingla, Qnlong, Jiama and Bangpu might constitute a potential metallogenic area dominated by skarn-type copper-lead-zinc polymetallic deposits.