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China is a center of diversity for Malus Mill. with 27 native species including 21 wild species and six domesticated species. We applied a set of 19 simple sequence repeat markers to genotype 798 accessions of 17 species (12 wild species and five cultivated species) of Malus originating from 14 provinces in China. A total of 500 alleles were detected. Diversity statistics indicated a high level of genetic variation as quantified by the average values of the effective allele number (Ne), expected heterozygosity (He), and Shannon’s Information Index (I) (10.309, 0.886, and 2.545, respectively). Malus sieversii (MSR; He=0.814, I=2.041, Ne=6.054), M. baccata (MBB; He=0.848, I=2.350, Ne=8.652), M. toringoides (MTH; He=0.663, I=1.355, Ne=3.332), and M. hupehensis (MHR; He=0.539, I=0.912, Ne=0.579) showed a higher level of genetic diversity in this study than the previous studies. MSR and MBB contributed to the origin and evolution of some accessions of M. domestica subsp. chinensis (MDC). However, other accessions of MDC showed a closer genetic distance with MBB and cultivated species, especially M. robusta (MRB), M. asiatica (MAN), and M. prunifolia (MPB). Not all accessions of MDC were descended from MSR in Xinjiang Uygur Autonomous Region of China. This research provides novel insights into the genetic relationships of Malus native to China, which will be useful for genetic association studies, germplasm conservation, and breeding programs.

Black rock as an important carrier of platinum group elements was discovered in recent years. Due to the multiple origins and complex mineralization, the distribution and occurrence of platinum group elements in black rock are not clear, which is also the major reason why the analytical results of platinum group elements are unstable. According to the mineral properties and composition of black rock, the occurrences of Pt, Pd and Au in black rock could be divided into exchangeable phase, organic binding phase, sulfide bounding phase, and residue phase. The adsorption of Pt, Pd and Au from the organic carbon in black rocks was inhibited by adding potassium thiocyanate and sodium cyanide as desorbents. The distribution of Pt, Pd and Au in each phase was identified by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The results show that: (1) The ratios of the total extraction of each phase to the total amount of the element are 94.4%-101.0% for Pt, 95.8%-101.0% for Pd, and 96.7%-102.0% for Au, indicating good accuracy and reproducibility. (2) The enrichment of Pt, Pd and Au in black rock minerals not only shows the chalcophile affinity, but also shows obvious correlation with the geological conditions and geological setting of organic carbon formation. The results provide important information for studying the geochemical environment and the metallogenic regularity of the platinum group elements in black rocks.

Extraction of elements of mobile forms is one of the important techniques in deep-penetrating geochemistry for finding concealed orebodies. However, the single extraction agent cannot be applied to all elements and all coverage areas. Moreover, the effective information of mobile forms is easily obscured because the extraction time, pH and extraction temperature have important effects on the extraction results. Determination of the mobile forms of multi-metal elements (W, Mo, Cu, Pb, Zn) in extractant using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) has been established. The optimum conditions include solid-liquid mixing ratio of 1:10, extraction time of 24 h, pH of 7.0, and an extraction temperature of 25℃. The determination limit of the proposed method is 0.006-0.021 μg/g and the relative standard deviation (RSD) is 1.91%-6.56%. This method has been applied to Xiyuku concealed porphyry Mo-W ore deposit in the Luanchuan ore concentrated district. The prospecting anomaly in mobile forms of W and Mo is consistent with the projection position of concealed orebodies in the ground surface.

Fire assay separation enrichment technology has been applied to precious metals analysis, however, its ingredients are complex, time-consuming, analysis costs are relatively high and blank controls are more difficult. A new method was set up such as the samples were dissolved with H2O2-HCl before Pt, Pd and Au were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In 10% hydrochloric acid solution, LSC-400 mercapto resin and activated carbon were mixed as the adsorbent. Pt，Pd and Au in the sample solution were separated and enriched by using dynamic adsorption. Lu was selected as the internal standard element to eliminate non-spectral interference and spectrum interference along with tracers of 195Pt, 197Au and 108Pd. The recovery rates of each element were more than 96.4%. The detection limits were 0.06 ng/g for Pt, 0.08 ng/g for Pd and 0.12 ng/g for Au. Compared with the detection limits, this established method was better than the fire assaying method and other separation and enrichment methods. The method has been applied to the determination of these elements in National Standard Materials for PGEs and results were in agreement with the certified values. The relative standard deviations (RSD, n=12) was less than 16.1%. The method is simple, low cost and greatly improves the speed of analysis，and effectively reduces the blanks of the chemical processing.