Paragenetic
Sequence of Sulfosalt Mineralization at Epithermal Deposits of
Southwestern Hokkaido, Japan
1Euis T.
YUNINGSIH and Hiroharu MATSUEDA
1
Faculty of Geology, University of Padjadjaran, Bandung, West Java, 45363
Indonesia (phone: +62 22 779 6545; fax: +62 22 779 6545; e-mail:
etintiny@yahoo.com).
2
Hokkaido University Museum, Hokkaido University, Sapporo, 060-0810 Japan
(e-mail: matsueda@museum.hokudai.ac.jp).
The
Shin Otoyo, Suttsu, Teine, Date, Chitose, and Koryu are precious and
base metals Miocene–Pleistocene epithermal deposits located at the
southwestern Hokkaido, Japan. The deposits are dominantly hosted by
green tuff formation of Middle Miocene age. The ore petrography study
from those deposits shows the occurrence of various amounts of
Cu–As–Sb–Ag–Bi–Pb–Te sulfosalt minerals. The determination of mineralogy
and chemical compositions of sulfosalt minerals from those deposits were
undertaken to provide information regarding conditions of ore formation
stability fields. Various kinds of sulfosalt minerals identified from
gold–silver and base metal quartz-sulfide veins were represented some
sulfosalt mineralization phases, such as Cu–Fe–Sn–S phase of mawsonite
and stannite; Cu–(As,Sb)–S phase of tetrahedrite–tennantite and
luzonite–famatinite series minerals; (Cu,Ag)–Bi–Pb–S phase of
emplectite, pavonite, friedrichite, aikinite, and lillianite–gustavite
series minerals; (Ag,Cu)–(As,Sb)–S phase of proustite–pyrargyrite and
pearceite–polybasite series minerals; and Bi–Te–S phase of tetradymite
and kawazulite minerals. In general there are some trends in the
paragenetic sequence of sulfosalt mineralization in southwestern
Hokkaido (in complete or partial) as follows: sulfide → Cu–Fe–Sn–S →
(Cu,Ag)–Bi–Pb–S → [Bi–Te–S] → Cu–(As,Sb)–S → [(Ag,Cu)–(As,Sb)–S]. The
formation of those sulfosalt minerals were characterized by the
introduction of some elements such as Sn, Bi, and Te at the earlier and
the increase or decrease of some elements such as As and Sb, and
followed by introduction of Ag at the later stages of ore mineral
paragenesis sequence. Thermodynamic stability for the Chitose and Koryu
are slightly different from those of Shin Otoyo, Suttsu, Teine, and Date
because of its lack of tin and bismuth mineralization. Their variability
concentrations and relationships are not simply with redistributed trace
elements from the original sulfides minerals, and some heavier elements
were also introduced during the replacement reaction which consistent
with their occurrence of their mineral associated with.
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