A systematic study combining U-Pb zircon dating,lithogeochemical and Sr-Nd isotopic analyses was carried out upon the Xinping granodiorite porphyry in the Dayaoshan metallogenic belt to understand its petrogenesis and...A systematic study combining U-Pb zircon dating,lithogeochemical and Sr-Nd isotopic analyses was carried out upon the Xinping granodiorite porphyry in the Dayaoshan metallogenic belt to understand its petrogenesis and tectonic significance.LA-ICP-MS U-Pb zircon dating yielded a 442.7±5.8 Ma age,indicating that the granodiorite porphyry was emplaced during the Llandovery Silurian of the Early Paleozoic.The granodiorite porphyry shares the same geochemical characteristics such as Eu negative anomaly as other syn-tectonic granite plutons in the region,including the granodiorite porphyry in Dawangding and granite porphyries in the Dali Cu-Mo deposit and Longtoushang old deposit,indicating a similar magma evolution process.The Xinping granodiorite porphyry has high contents of SiO2(67.871.8%)and K2O(1.78-3.42%)and is metaluminous-peraluminous with A/CNK ratios ranging from 0.97 to 1.06,indicative of high-potassium calc-alkaline to calc-alkaline affinity.It is a I-type granite enriched in large ion lithophile elements Rb,Sr,while depleted in Ba and high field-strength element Nb.Tectonically,a collision between the Yunkai Block from the south and the Guangxi Yunnan-North Vietnam Block from the north during the Early Paleozoic was followed by uplifting of the Dayaoshan terrane.The Xinping granodiorite porphyry was likely emplaced during the collision.Sr-Nd isotopic analyses show that the granodiorite porphyry has initial 87Sr/86Sr ratios(Isr)of 0.7080-0.7104,εNd(t)range from-0.08 to-4.09,and t2DM between 1.19 and 1.51 Ga,well within the north-east low-value zone of the Cathaysia block,indicating a Paleoproterozoic Cathaysia basement source and an involvement of under plating mantle magma.Field observations,geochronological data,and 3D spatial distribution all lead to the conclusion that the Early Paleozoic Xinping granodiorite porphyry does not have any metallogenic and temporal relationships with the Xinping gold deposit(which has a Jurassic-Early Cretaceous age based on previous studies)but a close metallogenic relation to W-Mo mineralization.展开更多
Quartz-vein-type copper deposits were discovered in SN-trend ore-bearing structures in north-west Dayaoshan,Guangxi.Lack of reports on the precise metallogenic age of these deposit has become a bottleneck in metalloge...Quartz-vein-type copper deposits were discovered in SN-trend ore-bearing structures in north-west Dayaoshan,Guangxi.Lack of reports on the precise metallogenic age of these deposit has become a bottleneck in metallogenic research in this area.In this study,the quartz vein-type copper mine in Longwei area of Jinxiu was selected as the research object.Fresh illite samples in the fault gouges and ore samples were collected for testing and analysis.Based on the Re-Os isotope dating study,the age of pyrite isochron,belonging to the Caledonian period,was determined to be 417±25 Ma,whereas that of chalcopyrite isochron belonging to the Indosinian period,was found to be 243±18 Ma.Pyrite crystallized considerably earlier than chalcopyrite.The obtained EPMA data were combined with rock mineralogical analysis data,Metasomatous mineral pyrite and metasomatic mineral chalcopyrite were identified to have originated from different hydrothermal systems.In the Indosinian period,copper deposits in the Longwei area underwent pyrite crystallization,pyrite fragmentation,copper-bearing hydrothermal filling,and metasomatism,consolidating and forming minerals.The study determined the mineralisation time and ore sources of copper deposits in the Longwei area.The study provides evidence for the existence of Indosinian hydrothermal activities in the north-western Dayaoshan area.展开更多
基金supported by the National Key R&D Program of China(2016YFC0600603)the Guangxi Science Foundation(2014GXNSFBA118230)the Foundation of Guilin University of Technology(GUTQDJJ2019166)。
文摘A systematic study combining U-Pb zircon dating,lithogeochemical and Sr-Nd isotopic analyses was carried out upon the Xinping granodiorite porphyry in the Dayaoshan metallogenic belt to understand its petrogenesis and tectonic significance.LA-ICP-MS U-Pb zircon dating yielded a 442.7±5.8 Ma age,indicating that the granodiorite porphyry was emplaced during the Llandovery Silurian of the Early Paleozoic.The granodiorite porphyry shares the same geochemical characteristics such as Eu negative anomaly as other syn-tectonic granite plutons in the region,including the granodiorite porphyry in Dawangding and granite porphyries in the Dali Cu-Mo deposit and Longtoushang old deposit,indicating a similar magma evolution process.The Xinping granodiorite porphyry has high contents of SiO2(67.871.8%)and K2O(1.78-3.42%)and is metaluminous-peraluminous with A/CNK ratios ranging from 0.97 to 1.06,indicative of high-potassium calc-alkaline to calc-alkaline affinity.It is a I-type granite enriched in large ion lithophile elements Rb,Sr,while depleted in Ba and high field-strength element Nb.Tectonically,a collision between the Yunkai Block from the south and the Guangxi Yunnan-North Vietnam Block from the north during the Early Paleozoic was followed by uplifting of the Dayaoshan terrane.The Xinping granodiorite porphyry was likely emplaced during the collision.Sr-Nd isotopic analyses show that the granodiorite porphyry has initial 87Sr/86Sr ratios(Isr)of 0.7080-0.7104,εNd(t)range from-0.08 to-4.09,and t2DM between 1.19 and 1.51 Ga,well within the north-east low-value zone of the Cathaysia block,indicating a Paleoproterozoic Cathaysia basement source and an involvement of under plating mantle magma.Field observations,geochronological data,and 3D spatial distribution all lead to the conclusion that the Early Paleozoic Xinping granodiorite porphyry does not have any metallogenic and temporal relationships with the Xinping gold deposit(which has a Jurassic-Early Cretaceous age based on previous studies)but a close metallogenic relation to W-Mo mineralization.
基金supported by the Natural Science Foundation of Shandong Province(Nos.ZR2020KE023 and ZR2021MD057)the National Natural Science Foundation of China(Grant No.42002282).
文摘Quartz-vein-type copper deposits were discovered in SN-trend ore-bearing structures in north-west Dayaoshan,Guangxi.Lack of reports on the precise metallogenic age of these deposit has become a bottleneck in metallogenic research in this area.In this study,the quartz vein-type copper mine in Longwei area of Jinxiu was selected as the research object.Fresh illite samples in the fault gouges and ore samples were collected for testing and analysis.Based on the Re-Os isotope dating study,the age of pyrite isochron,belonging to the Caledonian period,was determined to be 417±25 Ma,whereas that of chalcopyrite isochron belonging to the Indosinian period,was found to be 243±18 Ma.Pyrite crystallized considerably earlier than chalcopyrite.The obtained EPMA data were combined with rock mineralogical analysis data,Metasomatous mineral pyrite and metasomatic mineral chalcopyrite were identified to have originated from different hydrothermal systems.In the Indosinian period,copper deposits in the Longwei area underwent pyrite crystallization,pyrite fragmentation,copper-bearing hydrothermal filling,and metasomatism,consolidating and forming minerals.The study determined the mineralisation time and ore sources of copper deposits in the Longwei area.The study provides evidence for the existence of Indosinian hydrothermal activities in the north-western Dayaoshan area.
