Pb‐isotope compositions of the Tasik Chini volcanic‐hosted massive sulfide deposit, Central Belt of Peninsular Malaysia: Implication for source region and tectonic setting

Lead isotope data of sulfides and host volcanic rocks from the Bukit Botol and Bukit Ketaya deposits, the two representative deposits of the Tasik Chini volcanic‐hosted massive sulfide (VHMS) deposit, Central Belt of Peninsular Malaysia, are reported. Lead isotope compositions of the associated sulfide minerals and volcanic rocks from the Bukit Botol deposit exhibit homogeneous and less radiogenic values (206Pb/204Pb showing a range of composition from 18.14 to 18.20, 207Pb/204Pb between 15.52 and 15.59 and 208Pb/204Pb from 37.96 to 38.35). Similarly, the Pb isotopic compositions of the host volcanic rocks from the Bukit Ketaya deposit yielded a narrow range to those of the sulfide samples (206Pb/204Pb from 18.04 to 18.20, 207Pb/204Pb between 15.43 and 15.57 and 208Pb/204Pb of 37.96 to 38.30). The uniform Pb‐isotope compositions of the sulfides in the ore horizon and the host volcanic rocks from both deposits suggest a derivation from a similar source reservoir and mineralization processes. In the framework of the tectonic model for the Central Belt of Peninsular Malaysia, both deposits display a range of lead isotopic compositions originated from mixing of bulk crust/juvenile arc and minor mantle sources, which are typical for VHMS deposits in an island arc–back arc setting. マレーシア半島中央帯に位置するチニ湖火山岩類に胚胎した塊状硫化物鉱床の主要部をなすBukit Ketaya,Bukit Botol両鉱体の硫化物およびその母岩の火山岩の鉛同位体組成を測定した。Bukit Botol鉱体では硫化鉱物・火山岩とも一様かつ放射起源同位体の寄与の少ない値を示した(206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pbそれぞれ18.14‐18.20, 15.52‐15.59, 37.96‐38.35)。同様にBukit Ketaya鉱体の母岩の火山岩も硫化鉱物より狭い同位体組成範囲を示した(206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pbそれぞれ18.04–18.20,15.43–15.57,37.96–38.30)。これらの一様性は両鉱体の同源性および鉱化作用の類似性を示唆する。マレーシア半島中央帯のテクトニクスを考慮すると, 2つの鉱床が示すPb同位体比は初期島弧地殻に少量のマントル物質の混合によって説明でき, 島弧–背弧系の火山岩類に胚胎した塊状硫化物鉱床の典型と言える。 In this paper we present the results of Pb‐isotope data from the Tasik Chini VHMS deposits of Central Belt, Peninsular Malaysia. Additionally, we also constraint the source region of lead for VHMS mineralizations in the belt. Finally, we discuss and propose a tectonic setting for formation of VHMS deposits in the belt.