Fluid inclusions, C–H–O–S–Pb isotope systematics, geochronology and
geochemistry of the Budunhua Cu deposit, northeast China: Implications for
ore genesis
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Abstract
The Budunhua Cu deposit is located in the Tuquan ore-concentrated area of the southern Great Xing’an Range, NE
China. This deposit includes the southern Jinjiling and northern Kongqueshan ore blocks, separated by the
Budunhua granitic pluton. Cu mineralization occurs mainly as stockworks or veins in the outer contact zone
between tonalite porphyry and Permian metasandstone. The ore-forming process can be divided into four stages
involving stage I quartz–pyrite–arsenopyrite; stage II quartz–pyrite–chalcopyrite–pyrrhotite; stage III quartz-
–polymetallic sulfides; and stage IV quartz–calcite. Three types of fluid inclusions (FIs) can be distinguished in the
Budunhua deposit: liquid-rich two-phase aqueous FIs (L-type), vapour-rich aqueous FIs (V-type), and daughter
mineral-bearing multi-phase FIs (S-type). Quartz of stages I–III contains all types of FIs, whereas only L-type FIs
are evident in stage IV veins. The coexisting V- and S-type FIs of stages I–III have similar homogenization temperatures
but contrasting salinities, which indicates that fluid boiling occurred. The FIs of stages I, II, III, and IV
yield homogenization temperatures of 265–396 C, 245–350 C, 200–300 C, and 90–228 C with salinities of
3.4–44.3 wt.%, 2.9–40.2 wt.%, 1.4–38.2 wt.%, and 0.9–9.2 wt.% NaCl eqv., respectively. Ore-forming fluids of
the Budunhua deposit are characterized by high temperatures, moderate salinities, and relatively oxidizing
conditions typical of an H2O–NaCl fluid system. Mineralization in the Budunhua deposit occurred at a depth of
0.3–1.5 km, with fluid boiling and mixing likely being responsible for ore precipitation. C–H–O–S–Pb isotope
studies indicate a predominantly magmatic origin for the ore-forming fluids and materials. LA-ICP-MS zircon
U–Pb analyses indicate that ore-forming tonalite porphyry and post-ore dioritic porphyrite were formed at 151.1
1.1 Ma and 129.9 1.9 Ma, respectively. Geochemical data imply that the primary magma of the tonalite
porphyry formed through partial melting of Neoproterozoic lower crust. On the basis of available evidence, we
suggest that the Budunhua deposit is a porphyry ore system that is spatially, temporally, and genetically associated
with tonalite porphyry and formed in a post-collision extensional setting following closure of the Mongol–
Okhotsk Ocean.
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