http://d.hatena.ne.jp/garimpo/20161019 の昨年の探鉱結果が更新されている。 http://japangold.com/wp-content/uploads/2017/03/JG-2017-03-03-Ikutahara_Reg_Program.pdf
探鉱結果の地図だけ見ていても面白いが、サンプリングのやり方も書かれているので参考に・・・はならないけど面白い。
Stream Sediment Sampling and Analysis
Two samples each weighing about 2-3 kg were collected from the last deposited stream sediment of the active
creek channel at each sample site. The first sample was sieved to collect a minus 1.2 mm (16 mesh) fraction
sediment sample and the second sample was sieved to collect a minus 0.84 mm (20 mesh) fraction sediment sample.
The samples were packaged to prevent any contamination and dispatched under a secure chain-of-custody in two
separate batches to ALS Minerals in Perth, Australia for additional sample preparation and geochemical analysis.
The -1.2 mm fraction samples were weighed as received and then analyzed for gold-only by the Bulk Leach
Extractible Gold (‘BLEG’) technique by 12-hour bottle roll leach using dilute alkaline sodium cyanide solution
and then gold determination by ICPMS.
The -0.84 mm fraction samples were dried and further screened to obtain sufficient -180 micron (80 mesh) material
for gold analysis by 25g-charge aqua regia digestion/AAS finish and 49 multielement analysis (including arsenic,
antimony & mercury) off the same digestion with determination by ICPMS/AES.
Duplicate samples were collected from three sites to check the repeatability of results; the repeatability of results
was good. The laboratory inserts blanks, standards & sub-split pulp duplicates for Quality Control and reports
these results accordingly; these results fall within acceptable levels of accuracy and precision.
最後に堆積した川砂を2-3kg採って、篩い分け、粒度によって2種類の方法(青酸ナトリウムか王水)で金を抽出して分析装置にかける・・・と(ざっくり言えばこんな感じ？)
こういう調査では盤上の土砂じゃなくて、最後の堆積土砂(表面・・・とは限らないけど)でサンプリングするのだなあ。いろんな意味合いがあるのだろうけど。
