Early ezpulsion of PGMs from magmatic sulphide liquids: A new forensic technique using laser mapping
1 IntroductionWe all know that platinum-group elements (PGEs) are captured by magmatic sulphide liquids, which then crystallize to make exploration targets for Ni-Cu-PGE mineralisation. So why is it that the sulphide minerals consistently have extremely low contents for some PGEs, most notably Pt? And also, why is it common to find platinum-group minerals (PGMs), most notably Pt-minerals, around the margins of these same sulphides? This work follows on from previous studies using laser ablation ICP-MS (La ICP-MS), which traditionally employ a combination of line and spot analyses on in-situ sulphide minerals. We present results from a new La ICP-MS technique involving 2D laser mapping, which is revealing new information that is helping to answer the above questions. Sulphide-bearing samples from Norilsk and the Merensky Reef were investigated using this technique and the results are startling. In almost every case Pt is almost below detection and there are very few Pt-PGM inclusions locked within the sulphides. The same rocks can contain abundant Pt-PGMs, many of which show a clear spatial relationship to the sulphides. It seems more and more evident that Pt-bearing, and to a lesser extent Pd-bearing, minerals form prior to crystallisation of the sulphide liquids and that these are expelled to their margins. From here the PGMs can be remobilised into the surrounding silicates.
David Hutchinson Jeffrey G.Foster
CODES, ARC Centre of Excellence in Ore Deposits, University of Tasmania,Private Bag 79, Hobart TAS 7001, Australia
国际会议
Xian International Ni-Cu(Pt) Deposit Symposium 2009(2009 西安·Ni-Cu(Pt)岩浆矿床国际学术研讨会)
西安
英文
10-13
2009-09-01（万方平台首次上网日期，不代表论文的发表时间）