Genesis of the Changlingzi Zn--Pb deposit in the southern Great Xing'an Range, northeastern China: constraints from fluid inclusions and H--O--S--Pb isotope systematics

The Changlingzi Pb-Zn deposit is located in the southern Great Xing'an Range metallogenic belt of Northeast China. This deposit experienced two types of mineralization including skarn (ore block I) and hydrothermal vein (ore block II), and their orebodies are hosted mainly in the Lower Permian Zhesi Formation. The hydrothermal mineralization is classified into two metallogenic periods: skarn (stage 1) and sulfide (stages 2, 3, and 4). The skarn period affected only the ore block I, whereas the sulfide period similarly affected the two ore blocks. Fluid inclusion studies indicate that the ore-forming fluids during the early stage were medium- to high-temperature, high-salinity heterogeneous NaCl-[H.sub.2]O fluids, and that they eventually evolved to low-temperature, low-salinity homogeneous NaCl-[H.sub.2]O fluids by late stage. Studies of the hydrogen and oxygen isotope compositions ([[delta].sup.18][O.sub.H2O] = -13.85[per thousand] to 3.95[per thousand], [delta][D.sub.H2O] = -132.8[per thousand] to -102.7[per thousand]) show that the ore-forming fluids gradually evolved from magmatic water to meteoric water. Sulfur and lead date suggest that the ore-forming materials were probably derived from deep magma and the Permian strata. Although our data show that ore blocks I and II, in terms of genesis, were skarn- and medium-to low-temperature hydrothermal vein-types, respectively, the ore-forming fluids of both ore blocks were the same period, and the differences in mineralization type can be related to the wall rocks.Le gisement de Pb-Zn de Changlingzi est situe dans la partie meridionale de la ceinture metallogenique de la chaine du Grand Khingan du nord-est de la Chine. Le gisement a connu deux types de mineralisation, dont une skarnification (bloc mineralise I) et la formation de filons hydrothermaux (bloc mineralise II), les corps mineralises associes se trouvant principalement dans la Formation de Zhesi du Permien inferieur. La mineralisation hydrothermale est sous-divisee en deux periodes metallogeniques, a skarn (stade 1) et a sulfures (stades 2, 3 et 4). La periode de skarnification ne se manifeste que dans le bloc mineralise I. La periode de mineralisation en sulfures presente des elements semblables dans les deux blocs mineralises. L'etude des inclusions fluides indique que les fluides mineralisateurs durant le premier stade etaient des fluides heterogenes riches en NaCl-[H.sub.2]O de temperature moyenne a elevee et de forte salinite, qui ont fait place a des fluides homogenes riches en NaCl-[H.sub.2]O de faibles temperature et salinite aux stades de mineralisation plus tardifs. L'etude de la composition des isotopes d'hydrogene et d'oxygene ([[delta].sup.18][O.sub.H2O] = -13,85 [per thousand] a 3,95 [per thousand], [delta][D.sub.H2O] = -132,8 [per thousand] a -102,7 [per thousand]) montre que la source des fluides mineralisateurs est graduellement passee d'eau magmatique a de l'eau meteorique. Les donnees d'isotopes de soufre et de plomb indiqueraient que les materiaux mineralisateurs etaient probablement derives de magma profond et des strates permiennes. Si nos donnees montrent que, du point de vue de leur formation, les blocs mineralises I et II etaient, respectivement, de types skarn et filons hydrothermaux de temperature moyenne a faible, les fluides mineralisateurs des deux blocs etaient contemporains, et les differents types de mineralisation peuvent etre relies a la nature des roches encaissantes. [Traduit par la Redaction]
IntroductionThe southern Great Xing'an Range (SGXR) is an important metallogenic belt in northeastern China (Liu et al. 2004; Wang et al. 2001; Zeng et al. 2011). Since the late Paleozoic, [...]