Yuling Xie

Formation of carbonatite-related giant rare-earth-element deposits by the recycling of marine sediments

Carbonatite-associated rare-earth-element (REE) deposits are the most significant source of the world’s REEs; however, their genesis remains unclear. Here, we present new Sr-Nd-Pb and C-O isotopic data for Cenozoic carbonatite-hosted giant REE deposits in southwest China. These REE deposits are located along the western margin of the Yangtze Craton that experienced Proterozoic lithospheric accretion, and controlled by Cenozoic strike-slip faults related to Indo-Asian continental collision. The Cenozoic carbonatites were emplaced as stocks or dykes with associated syenites, and tend to be extremely enriched in Ba, Sr, and REEs and have high 87Sr/86Sr ratios (>0.7055). These carbonatites were likely formed by melting of the sub-continental lithospheric mantle (SCLM), which had been previously metasomatized by high-flux REE- and CO2-rich fluids derived from subducted marine sediments. The fertility of these carbonatites depends on the release of REEs from recycled marine sediments and on the intensity of metasomatic REE refertilization of the SCLM. We suggest that cratonic edges, particularly along ancient convergent margins, possess the optimal configuration for generating giant REE deposits; therefore, areas of metamorphic basement bounded or cut by translithospheric faults along cratonic edges have a high potential for such deposits.

Optimising sampling protocols via the heterogeneity test: challenges in coarse gold mineralisation

Determination of the sampling constant is an important step when applying the Fundamental Sampling Error equation to optimise sampling protocols. The classic method for its determination is based on the heterogeneity test (HT). In coarse gold-dominated mineralisation, the HT sometimes provides an evaluation of the fine-gold background grade population heterogeneity, but understates that of the important high-grade coarse-gold component. This is because the total mass of fragments is too small to represent the full gold particle size distribution of the mineralisation. Despite this, single heterogeneity tests (SHT) are often undertaken on deposits where the presence of coarse gold is ignored, not realised or understated. Resultant sampling and assaying protocols are frequently of poor quality and do not match the mineralisation characteristics. For coarse gold-dominated mineralisation, an empirical approach for sampling constant determination is recommended via direct estimation of the liberation diameter.

Ore Genesis and Deposit Model of Carbonatite‐host REE Deposits: the Mianning‐Dechang REE Belt, Western Sichuan Province, China

Carbonatite-related deposits host the majority of world’s REE resources. Key examples of carbonatite REE mineralized systems include the Bayan Obo, China, Mountain Pass deposit, USA and Maoniuping, China. The Himalayan Mianning-Dechang (MD) belt in western Sichuan, SW China is one of the most significant REE belts in China. It hosts the giant Maoniuping deposit (3.17Mt REO, 109 Geological Brigade of Sichuan Bureau of Geology and Mineral Resource, 2010), two intermediate, a number of small REE deposits and REE occurrences. Based on geological and geochemical results from key deposits, this paper provides a new understanding on the ore-forming processes and proposes a new deposit model for carbonatite hosted REE deposit.

Characteristics of carbonatite fluid in the Maoniuping REE deposit, Mianning, China

The Maoniuping rare earth elements (REE) deposit, located in the Mianning — Dechang REE metallogenetic belt on the west margin of the Yangtze Craton, is related to a Himalayan carbonatite and alkalic rock association. Fluid inclusion studies revealed three types of inclusions in quartz, fluorite, calcite and barite, including melt inclusions (M type), melt-fluid inclusions (ML type) and fluid inclusions (L type). Microthermometry, SEM/EDS and LRM was performed on M type inclusions and L type inclusions in fluorite, barite and quartz. The results show that the ore-forming fluid could be derived from a carbonatite and was a high temperature, high pressure, K-rich, CO2-rich, multi-component fluid.

An inexact multi-objective programming model for water resources management in industrial parks of Binhai New Area, China

In recent years, Binhai New Area of Tianjin has been suffering severe water shortage due to climate change and industrial activities. Integrated and effective water resources management approaches are urgent for the sustainable development of industrial parks in Binhai New Area. However, uncertainties exist in many aspects of the water resources system and are inevitably problematic for water resources planning and policy-making. To address these uncertainties, an interval multiple-objective programming model was developed here to support the long-term planning of industrial water resources management in Binhai New Area, Tianjin, China. The model incorporated both multiple-objective programming and interval linear programming into a general programming framework. The developed model could handle the uncertainties and complexities of the water management system, and also allowed decision makers to adjust fuzzy objective control decision variables to satisfy multiple holistic and interactive objectives. The solutions are useful for planning adjustments of the existing water allocation patterns in Binhai New Area.

The Characteristics and Evolution of Ore‐forming Fluids in A'erhada Pb‐Zn‐Ag Deposit, Inner Mongolia, China

The A’erhada Pb-Zn-Ag deposit, located in Dongwuqi, Inner Mongolia, is one of the largest Pb-Zn-Ag deposits in this region. The geology and geochemistry of this deposit have been reported by Tao (2006), Gao and Qian (2005) and Zhang et al., (2007), but not much research address the ore forming fluids and their evolution in this deposit. The ore genesis is still open to debate. Based on the field observation, ore-microscopic, petrographic, microthermometric, LRM (Laser Raman Microsprobe) and H-O isotopic results of fluid inclusions in quartz from various mineralization stages, this paper discusses the characteristics and the evolution of ore-forming fluid.

Characteristics and evolution of ore-forming fluids of the Chongjiang copper deposit in the Gangdise porphyry copper belt, Tibet

Abstract Petrography, microthermometry, and scanning electron microscope/energy dispersive spectrometer (SEM/EDS) studies were performed on the fluid inclusions in the ore-bearing quartz veins and quartz phenocrysts in the porphyry of the Chongjiang porphyry copper deposit. The analyses of the fluid inclusions indicate that the ore-forming fluids were exsolved from magma. They are near-saturated, supercritical, rich in volatile constituents, and have the capture temperature of 362–389°C and salinities of 17.7wt%-18.9wt% NaCl eq. With the decreasing of temperature and pressure, the supercritical fluids were separated into a low salinity vapor phase and a high salinity liquid phase. During quartz-sericitization, the high salinity fluid boiled and separated into a low salinity vapor phase and a high salinity liquid phase. The high salinity inclusions that formed in the boiling process had daughter mineral melting temperatures higher than the homogenization temperatures of the vapor and liquid phases. The late fluids that are responsible for argillization are of lower temperature and salinity.

Muluozhai REE deposit in Sichuan Province, China: Stable isotope data and their implications on the dynamics of mineralization

The Muluozhai REE deposit, located about 60 km to the southwest of the Mianning county, Sichuan Province, is the third largest light REE deposit in Sichuan. The Muluozhai REE deposit is tectonically located on the northern Jinpingshan Mountains, a Cenozoic intracontinental orogenic belt in southwestern China. The authors analyzed the essential ores from two tunnels for their carbon, hydrogen, oxygen, and sulfur isotopic compositions of the mineralizing fluid. The δ13CV-PDB values of fluid from fluid inclusions of the quartz and fluorite vary from −2.5 to −9.0 per mil, which show characteristics of mantle-derived carbon. The δDV-SMOW values of fluid from fluid inclusions of the calcite, quartz, fluorite, and bastnaesite range from −63 to −87 per mil, which are characteristics of mantle-derived hydrogen. The δ34SV-CDT values of barite and galena vary in a narrow range of +0.1 to +2.2 per mil and −8.6 to −9.3 per mil, respectively, showing the isotopic characteristics of mantle-derived sulfur. The δ13CV-PDB values and the δ18OV-SMOW values of calcite range from −6.6 to −6.8 per mil and from +8.4 to +9.1 per mil, respectively, which are fallen into the range of the “primary carbonatites”, showing the carbon and oxygen in the ores of the Muluozhai ore veins were mainly derived from depths. The stable isotopic data suggest a mantle source for the rare earth elements mineralization and a dynamic process involving mantle materials and tectonics.