{"title":"坦桑尼亚南部Mkuju河铀项目地表样品的地球化学特征:对铀地球化学勘探和物源研究的影响","authors":"Athanas S. Macheyeki , Dalaly P. Kafumu","doi":"10.1016/j.oreoa.2025.100107","DOIUrl":null,"url":null,"abstract":"<div><div>Uranium occurrences in Tanzania are mainly associated with Karoo Formations, including the Namtumbo-Mkuju River and Madaba deposits. Additional occurrences are found in Quaternary-Holocene playa lake deposits in the Manyoni and Bahi areas (Central Tanzania), Galapo and Minjingu (Arusha region) and within magmatic and carbonatite systems at Chimala and Pandahill (Southwestern Tanzania). This study focuses on the Mkuju River uranium deposits in southern Tanzania to characterize elemental distributions, identify geochemical trends and determine uranium provenance. A total of 64 auger samples were collected from depths of 0–3 m at 1 km × 1 km grid intervals. Samples were analyzed using ICP-AES and ICP-MS following aqua regia digestion at SGS Laboratories (South Africa), with duplicates analyzed via XRF at the Geological Survey of Tanzania. Correlation coefficients (R) between uranium and other elements range from -0.07 (Ti) to 0.79 (Zn). Stronger correlations (<em>R</em> > 0.47) were observed between uranium and lithophile elements, or those with mixed lithophile-siderophile or chalcophile-siderophile behavior, indicating multiple uranium sources. Element thresholds varied with depth. Uranium, Sn and Sb showed increasing thresholds, whereas Hf, P, Ca, Zr, Co, Al, Ti, Rb, Sr, Na, Tl, Th, Mn and Cr decreased. Uranium concentrations exceeding 4.65 ppm are considered anomalous. Downhole threshold variability was element-specific. For example, W showed 0 % variability, Mo (siderophile / chalcophile) 12 %, and Cu, Ga, Sn (chalcophile / lithophile) ranged from 10 to 29 %. HFSE lithophiles like Hf and Ta varied by 12–25 %, while chalcophiles such as Zn, Pb, In, As, Tb, Bi, Ag and Cd ranged from 4 to 26 %. Siderophile / chalcophile elements like Co, Fe, Sb and Ni exhibited 6–29 % variability. Lithophiles (e.g., U, V, K, Al, Ce, Mg) varied by 5–40 %. Mn, a siderophile, had the highest variability at 43 %. Geochemical data suggest uranium anomalies in the Namtumbo area originate mainly from greywackes, arkosic sandstones, black shales and partially from weathered igneous granites. This implies a multi-source origin involving sedimentary input, hydrothermal diagenesis and hydrothermal magmatic-volcanic activity. Therefore, uranium in this basin likely formed through (1) syn-sedimentary processes, (2) diagenetic alteration, and (3) magmatic-hydrothermal systems. However, the absence of Eh and pH data limits insight into element mobility. These findings provide new insights into downhole element threshold variability and uranium provenance, offering valuable guidance for exploration geoscientists. The approach may be applied to similar geological contexts for improved sampling strategies and anomaly detection.</div></div>","PeriodicalId":100993,"journal":{"name":"Ore and Energy Resource Geology","volume":"19 ","pages":"Article 100107"},"PeriodicalIF":0.0000,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Geochemical characteristics of surface samples in the Mkuju River uranium project, southern Tanzania: implications for uranium geochemical exploration and provenance studies\",\"authors\":\"Athanas S. Macheyeki , Dalaly P. Kafumu\",\"doi\":\"10.1016/j.oreoa.2025.100107\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Uranium occurrences in Tanzania are mainly associated with Karoo Formations, including the Namtumbo-Mkuju River and Madaba deposits. Additional occurrences are found in Quaternary-Holocene playa lake deposits in the Manyoni and Bahi areas (Central Tanzania), Galapo and Minjingu (Arusha region) and within magmatic and carbonatite systems at Chimala and Pandahill (Southwestern Tanzania). This study focuses on the Mkuju River uranium deposits in southern Tanzania to characterize elemental distributions, identify geochemical trends and determine uranium provenance. A total of 64 auger samples were collected from depths of 0–3 m at 1 km × 1 km grid intervals. Samples were analyzed using ICP-AES and ICP-MS following aqua regia digestion at SGS Laboratories (South Africa), with duplicates analyzed via XRF at the Geological Survey of Tanzania. Correlation coefficients (R) between uranium and other elements range from -0.07 (Ti) to 0.79 (Zn). Stronger correlations (<em>R</em> > 0.47) were observed between uranium and lithophile elements, or those with mixed lithophile-siderophile or chalcophile-siderophile behavior, indicating multiple uranium sources. Element thresholds varied with depth. Uranium, Sn and Sb showed increasing thresholds, whereas Hf, P, Ca, Zr, Co, Al, Ti, Rb, Sr, Na, Tl, Th, Mn and Cr decreased. Uranium concentrations exceeding 4.65 ppm are considered anomalous. Downhole threshold variability was element-specific. For example, W showed 0 % variability, Mo (siderophile / chalcophile) 12 %, and Cu, Ga, Sn (chalcophile / lithophile) ranged from 10 to 29 %. HFSE lithophiles like Hf and Ta varied by 12–25 %, while chalcophiles such as Zn, Pb, In, As, Tb, Bi, Ag and Cd ranged from 4 to 26 %. Siderophile / chalcophile elements like Co, Fe, Sb and Ni exhibited 6–29 % variability. Lithophiles (e.g., U, V, K, Al, Ce, Mg) varied by 5–40 %. Mn, a siderophile, had the highest variability at 43 %. Geochemical data suggest uranium anomalies in the Namtumbo area originate mainly from greywackes, arkosic sandstones, black shales and partially from weathered igneous granites. This implies a multi-source origin involving sedimentary input, hydrothermal diagenesis and hydrothermal magmatic-volcanic activity. Therefore, uranium in this basin likely formed through (1) syn-sedimentary processes, (2) diagenetic alteration, and (3) magmatic-hydrothermal systems. However, the absence of Eh and pH data limits insight into element mobility. These findings provide new insights into downhole element threshold variability and uranium provenance, offering valuable guidance for exploration geoscientists. The approach may be applied to similar geological contexts for improved sampling strategies and anomaly detection.</div></div>\",\"PeriodicalId\":100993,\"journal\":{\"name\":\"Ore and Energy Resource Geology\",\"volume\":\"19 \",\"pages\":\"Article 100107\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2025-05-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Ore and Energy Resource Geology\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S2666261225000252\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Ore and Energy Resource Geology","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S2666261225000252","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Geochemical characteristics of surface samples in the Mkuju River uranium project, southern Tanzania: implications for uranium geochemical exploration and provenance studies
Uranium occurrences in Tanzania are mainly associated with Karoo Formations, including the Namtumbo-Mkuju River and Madaba deposits. Additional occurrences are found in Quaternary-Holocene playa lake deposits in the Manyoni and Bahi areas (Central Tanzania), Galapo and Minjingu (Arusha region) and within magmatic and carbonatite systems at Chimala and Pandahill (Southwestern Tanzania). This study focuses on the Mkuju River uranium deposits in southern Tanzania to characterize elemental distributions, identify geochemical trends and determine uranium provenance. A total of 64 auger samples were collected from depths of 0–3 m at 1 km × 1 km grid intervals. Samples were analyzed using ICP-AES and ICP-MS following aqua regia digestion at SGS Laboratories (South Africa), with duplicates analyzed via XRF at the Geological Survey of Tanzania. Correlation coefficients (R) between uranium and other elements range from -0.07 (Ti) to 0.79 (Zn). Stronger correlations (R > 0.47) were observed between uranium and lithophile elements, or those with mixed lithophile-siderophile or chalcophile-siderophile behavior, indicating multiple uranium sources. Element thresholds varied with depth. Uranium, Sn and Sb showed increasing thresholds, whereas Hf, P, Ca, Zr, Co, Al, Ti, Rb, Sr, Na, Tl, Th, Mn and Cr decreased. Uranium concentrations exceeding 4.65 ppm are considered anomalous. Downhole threshold variability was element-specific. For example, W showed 0 % variability, Mo (siderophile / chalcophile) 12 %, and Cu, Ga, Sn (chalcophile / lithophile) ranged from 10 to 29 %. HFSE lithophiles like Hf and Ta varied by 12–25 %, while chalcophiles such as Zn, Pb, In, As, Tb, Bi, Ag and Cd ranged from 4 to 26 %. Siderophile / chalcophile elements like Co, Fe, Sb and Ni exhibited 6–29 % variability. Lithophiles (e.g., U, V, K, Al, Ce, Mg) varied by 5–40 %. Mn, a siderophile, had the highest variability at 43 %. Geochemical data suggest uranium anomalies in the Namtumbo area originate mainly from greywackes, arkosic sandstones, black shales and partially from weathered igneous granites. This implies a multi-source origin involving sedimentary input, hydrothermal diagenesis and hydrothermal magmatic-volcanic activity. Therefore, uranium in this basin likely formed through (1) syn-sedimentary processes, (2) diagenetic alteration, and (3) magmatic-hydrothermal systems. However, the absence of Eh and pH data limits insight into element mobility. These findings provide new insights into downhole element threshold variability and uranium provenance, offering valuable guidance for exploration geoscientists. The approach may be applied to similar geological contexts for improved sampling strategies and anomaly detection.