TY - JOUR
T1 - Testing the Plagioclase Discriminator on the GEOROC Database to Identify Porphyry-Fertile Magmatic Systems in Japan
AU - Williamson, Benedict J.
AU - Hodgkinson, Matthew
AU - Imai, Akira
AU - Takahashi, Ryohei
AU - Armstrong, Robin N.
AU - Herrington, Richard J.
N1 - Funding Information:
The project would not have been possible without the financial and logistical support of the Daiwa Foundation and funding from the Natural Environment Research Council project “FAMOS” (NE/P017452/1)
Publisher Copyright:
© 2018 The Society of Resource Geology
PY - 2018/4
Y1 - 2018/4
N2 - Despite showing favorable geology, there are no known porphyry-type deposits in Japan. This, therefore, provides an ideal porphyry-“barren” case area on which to test the recently developed plagioclase-based discriminator for porphyry-“fertile” calc-alkaline systems. The discriminator was applied to plagioclase data for Japan in the online GEOROC database for convergent margin settings. Of the 3933 data points available, and considered reliable, 91% fall in the “barren” field, which compares with 73% for equivalent data worldwide. “Fertile” signatures in certain parts of Kyushu and central Honshu should be further investigated, as well as areas where there are magnetite-series magmatic systems with elevated whole-rock Sr/Y but for which there are currently little or no plagioclase data (SW-, N-central-, and NE-Honshu). Why the Japanese arcs appear to show anomalously poor potential for porphyry deposits compared with other arcs worldwide, including Western Luzon, is as yet unclear but possibly relates to tectonic factors or the nature of the magmatic source or because melt PH2O in many of the magmatic systems was too low, as suggested from low average excess Al in plagioclase.
AB - Despite showing favorable geology, there are no known porphyry-type deposits in Japan. This, therefore, provides an ideal porphyry-“barren” case area on which to test the recently developed plagioclase-based discriminator for porphyry-“fertile” calc-alkaline systems. The discriminator was applied to plagioclase data for Japan in the online GEOROC database for convergent margin settings. Of the 3933 data points available, and considered reliable, 91% fall in the “barren” field, which compares with 73% for equivalent data worldwide. “Fertile” signatures in certain parts of Kyushu and central Honshu should be further investigated, as well as areas where there are magnetite-series magmatic systems with elevated whole-rock Sr/Y but for which there are currently little or no plagioclase data (SW-, N-central-, and NE-Honshu). Why the Japanese arcs appear to show anomalously poor potential for porphyry deposits compared with other arcs worldwide, including Western Luzon, is as yet unclear but possibly relates to tectonic factors or the nature of the magmatic source or because melt PH2O in many of the magmatic systems was too low, as suggested from low average excess Al in plagioclase.
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U2 - 10.1111/rge.12162
DO - 10.1111/rge.12162
M3 - Article
AN - SCOPUS:85044638868
SN - 1344-1698
VL - 68
SP - 138
EP - 143
JO - Resource Geology
JF - Resource Geology
IS - 2
ER -