Rare earth element and yttrium analyses of sulfides from the Dachang Sn-polymetallic ore field, Guangxi Province, China: Implication for ore genesis

Abstract

The Dachang Sn-polymetallic ore field (Guangxi, China) is one of the largest tin deposits in the world with a tin reserve of above 10 6 tons. Several types of orebody occur in this giant ore field, including mainly the Lamo Cu-Zn skarns at the contact of Devonian limestone and the Cretaceous Longxianggai granite, the Changpo-Tongkeng stratiform Sn-PbZn ores in Devonian siliceous rocks, and the Gaofeng massive sulfide ore in Devonian reef limestone. Rare-earth element (REE) and yttrium concentrations in sulfides from different orebody types have been determined by ICP-MS. Sulfides from the Lamo skarn-type Cu-Zn mines display significant LREE-enriched pattern with large negative Eu anomalies. This is in agreement with the mineralizing fluid being of magmatic hydrothermal origin. However, sulfides from massive and stratiform orebodies show significantly different REE distributions. The Gaofeng massive sulfides have very low total REE concentrations and REE patterns range from (1) being strongly enriched in light REE with positive Eu anomalies, to (2) relatively flat patterns with strongly negative Ce and positive Eu anomalies. Pattern 1 resembles REE distributions in modern submarine hydrothermal fluids. Pattern 2 exhibits both seawater and hydrothermal vent-fluid characteristics. Sulfides from stratiform orebodies at Changpo-Tongkeng are LREE-enriched with small or no negative Eu anomalies. REE patterns of sulfides from different stratiform orebodies are slightly different, but they are similar to those of each host rock. It indicates that the sulfides and host rocks are synsedimentary and that their REE patterns are controlled by the local physical-chemical environments. Y/Ho atomic weight ratios of granite, skarn and sulfides at Lamo vary from 26.3 to 33.7, close to the chondritic Y/Ho ratio. But sulfides from massive and stratiform ores have more variable Y/Ho ratios (28.4-134) that are similar to those of many modern hydrothermal fluids. Hence, the ore-forming fluids responsible for mineralization of the stratiform and massive ores at Dachang were likely to be of exhalative hydrothermal origin. It is suggested that the Dachang deposits are formed through a two-stage hydrothermal process, i.e., the Devonian submarine hydrothermal ore-forming stage and the Yanshanian magmatic-hydrothermal ore-forming stage.

Iron isotope investigation of hydrothermal and sedimentary pyrite and their aqueous dissolution products

“…1). This is consistent with precipitation from a hydrothermal fluid which may have interacted with multiple rock types before and during pyrite crystallization (Fralick et al, 1989;Mills and Elderfield, 1995;Chen et al, 1998;Zhao and Jiang, 2007).…”

“…REE concentrations can provide information about the source of solutes in solutions associated with pyrite formation. Because the REE do not readily substitute for major constituents in the pyrite structure, they are thought to be held in fluid inclusions or crystal defects (Zhao and Jiang, 2007), and the patterns reflect those of the mineralizing fluids (Mills and Elderfield, 1995;Song et al, 1997). The REE concentrations in most of the pyrite samples analyzed here fell below chondritic values (Anders and Grevasse, 1989), with the exceptions of SED-COAL-2 and HY-3 ( Table 2, Fig.…”

The source of Fengjia and Langxi barite–fluorite deposits in southeastern Sichuan, China: evidence from rare earth elements and S, Sr, and Sm–Nd isotopic data

“…Isotopic geochemistry tracing is one of the most powerful tools to determine the characteristics of the ore‐forming sources (Pattrick and Bowell, ; Zheng and Chen, ; Deng et al , ; Wang et al , , b; Yue et al , ; Zhang et al , ). Rare earth element (REE) geochemistry studies can also provide information regarding the sources of ore‐forming materials (Zhao and Jiang, ). Likewise, sulphur and strontium isotopes can be used to trace the sources of S, Ca, Sr, and Ba in metallogenic systems effectively (Ruiz and Kesler, ; Barbieri and Bellanca, ; Hoefs, ; Jiang et al , ; Chen et al , , ; Zhu et al , ; Li et al , ; Wang et al , ; ).…”

Linear Correlation of Ba and Eu Contents by Hydrothermal Activities: A Case Study in the Hetang Formation, South China

“…Positive Eu anomalies have also been widely reported in modern deep-sea hydrothermal systems [7][8][9] and in massive deposits of submarine hydrothermal exhalative origin [10][11][12]. Consequently, it has been used as an effective tracer for tracking and characterizing hydrothermal activities in sedimentary rocks and ore deposits [13][14][15][16][17][18][19]. In addition, in spite of no direct evidence showing europium reduction under surface conditions, positive Eu anomalies might be present at highly reducing conditions during diagenesis.…”