CAJ | 학술논문

硫、氧同位素和放射性同位素比值在示踪岩浆与围岩的反应及在岩浆镍-铜-铂族元素矿床成因中同化过程的重要性方面有很大作用.如1.1 Ga的Duluth杂岩、Noril'sk地区二叠-三叠纪侵入岩和1.4 Ga的Kabanga侵入岩体中矿床的硫同位素测定结果证明硫来自含硫化物和硫酸盐的围岩.1.3 Ga的Voisbey's Bay矿床矿石的硫同位素δ34S值通常落入公认的地幔硫同位素组成范围(0±2‰)内,而对其元古宙变质沉积围岩进行的详细研究结果显示δ34S的平均值也在此范围.全面了解同位素组成的潜在混染对合理评价提供硫来源的围岩在矿石形成中的作用是非常必要的.用氧同位素和放射性同位素示踪岩浆和围岩相互作用时,必须在开放体系没有扰动同位素系统情况下进行.在氧同位素体系和放射性同位素体系(如Re/Os、Pb同位素体系)中,元素在热液条件下活动性强或主相没有发生同位素交换与吸收,都会导致低温热液过程掩盖高温过程.只有在进行详细的岩相观察和单矿物分析之后,再应用围岩混染同位素模式才是有意义的.
류、양동위소화방사성동위소비치재시종암장여위암적반응급재암장얼-동-박족원소광상성인중동화과정적중요성방면유흔대작용.여1.1 Ga적Duluth잡암、Noril'sk지구이첩-삼첩기침입암화1.4 Ga적Kabanga침입암체중광상적류동위소측정결과증명류래자함류화물화류산염적위암.1.3 Ga적Voisbey's Bay광상광석적류동위소δ34S치통상락입공인적지만류동위소조성범위(0±2‰)내,이대기원고주변질침적위암진행적상세연구결과현시δ34S적평균치야재차범위.전면료해동위소조성적잠재혼염대합리평개제공류래원적위암재광석형성중적작용시비상필요적.용양동위소화방사성동위소시종암장화위암상호작용시,필수재개방체계몰유우동동위소계통정황하진행.재양동위소체계화방사성동위소체계(여Re/Os、Pb동위소체계)중,원소재열액조건하활동성강혹주상몰유발생동위소교환여흡수,도회도치저온열액과정엄개고온과정.지유재진행상세적암상관찰화단광물분석지후,재응용위암혼염동위소모식재시유의의적.
Measurements of S, O, and radiogenic isotope ratios are all potentially powerful tracers of magma interaction with country rocks and the importance of assimilation processes in the genesis of magmatic Ni-CuPGE deposits. Sulfur isotope measurements of deposits such as those in the 1.1 Ga Duluth Complex, the Permo-Triassic intrusions of the Noril'sk area, and the 1.4 Ga Kabanga intrusions provide evidence for the derivation of S from both sulfide-and sulfate-bearing country rocks. The 1.3 Ga Voisey's Bay deposit provides an example where δ34S values of the ores commonly fall within the accepted mantle range of 0 ± 2‰, but detailed studies of Proterozoic metasedimentary country rocks show that their weighted average δ34S value is also within this range. A thorough knowledge of the isotopic compositions of potential contaminants is essential for a proper evaluation of the role of country rock derived S in ore formation. When O and radiogenic isotopic measurements are employed as tracers to evaluate magma-country rock interaction it is essential to provide evidence that open system processes have not perturbed the isotopic systematics. Low-temperature hydrothermal processes can mask evidence of high-temperature processes in the oxygen isotope system, and in radiogenic systems such as Re/Os and Pb where involved elements may be mobile under hydrothermal conditions, or host phases may close to exchange and uptake at different temperatures. Careful petrographic observation and analyses of individual minerals may be required before the models involving the contamination of magmas by country rocks can be meaningfully applied.