{"title":"Hydrothermal rutile chemistry and U-Pb age fingerprinting of the formation of the giant Nurkazgan porphyry Cu-Au deposit, Central Kazakhstan","authors":"Haoxuan Feng , Reimar Seltmann , Ping Shen , Xiangkai Chu , Qingyu Suo , Eleonora Seitmuratova , Vitaly Shatov","doi":"10.1016/j.oregeorev.2024.106293","DOIUrl":null,"url":null,"abstract":"<div><div>The porphyry Cu-related intrusions commonly comprise multiple phases such as the large Nurkazgan porphyry Cu-Au deposit in Central Kazakhstan, hosted in the Karagandinsky dioritic to granitic intrusive complex. Here, SHRIMP and LA-ICP-MS zircon U-Pb dating on the multiple ore-bearing intrusions from this complex confirms a punctuated magmatic history distributed over 35 m.y., and marked by three episodic porphyry events rather than a single event, with the oldest event being the early granodiorite and quartz diorite porphyries at ca. 437–440 Ma, the second being the quartz diorite porphyry at 429.7 ± 2.1 Ma, and the last being the late granodiorite and quartz diorite porphyries at 402.8 ± 3.7 Ma and 402.0 ± 3.9 Ma, respectively. The mineralization is related to the two younger episodic intrusions of quartz diorite porphyry at ∼ 430 Ma and ∼ 402 Ma, respectively. SIMS U-Pb dating of hydrothermal, Cu-rich (up to 20.9 ppm) rutile from the breccia-type ores directly constrains the timing of porphyry mineralization at 428.9 ± 6.9 Ma, which is coincident with the emplacement age of the ∼ 430 Ma quartz diorite porphyry, and thus demonstrates this porphyry as a causative intrusion generating main-stage mineralization. This close genetic link is also supported by the chondrite-normalized REE patterns of rutile, which show remarkably similar light REE-enrichments and moderate negative Eu anomalies to those of the ∼ 430 Ma quartz diorite porphyry. A molybdenite sample obtained from the main-ore stage vein, however, has a Re-Os age of 418.6 ± 1.8 Ma, which is slightly younger than the U-Pb age determinations of rutile. This indicates that the Re-Os isotope system was disturbed by the second (post-ore) thermal event related to ∼ 402 Ma quartz diorite porphyry. In line with published data, this study suggests that the rutile U-Pb age in combination with its REE patterns can be a powerful tool to trace the causative porphyry. Moreover, the typical LREE-enriched REE patterns coupled with the high Cu anomalies, inherited from the causative porphyry and related exsolving fluids, can be as diagnostic proxies for distinguishing the porphyry Cu-related hydrothermal rutile from those formed in orogenic gold deposits. Based on these two geochemical discriminators and U-Pb ages, rutile can serve as unique fingerprints to help improve porphyry copper exploration in green field or covered terranes to complement detrital zircon fertility indicators.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Ore Geology Reviews","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0169136824004268","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The porphyry Cu-related intrusions commonly comprise multiple phases such as the large Nurkazgan porphyry Cu-Au deposit in Central Kazakhstan, hosted in the Karagandinsky dioritic to granitic intrusive complex. Here, SHRIMP and LA-ICP-MS zircon U-Pb dating on the multiple ore-bearing intrusions from this complex confirms a punctuated magmatic history distributed over 35 m.y., and marked by three episodic porphyry events rather than a single event, with the oldest event being the early granodiorite and quartz diorite porphyries at ca. 437–440 Ma, the second being the quartz diorite porphyry at 429.7 ± 2.1 Ma, and the last being the late granodiorite and quartz diorite porphyries at 402.8 ± 3.7 Ma and 402.0 ± 3.9 Ma, respectively. The mineralization is related to the two younger episodic intrusions of quartz diorite porphyry at ∼ 430 Ma and ∼ 402 Ma, respectively. SIMS U-Pb dating of hydrothermal, Cu-rich (up to 20.9 ppm) rutile from the breccia-type ores directly constrains the timing of porphyry mineralization at 428.9 ± 6.9 Ma, which is coincident with the emplacement age of the ∼ 430 Ma quartz diorite porphyry, and thus demonstrates this porphyry as a causative intrusion generating main-stage mineralization. This close genetic link is also supported by the chondrite-normalized REE patterns of rutile, which show remarkably similar light REE-enrichments and moderate negative Eu anomalies to those of the ∼ 430 Ma quartz diorite porphyry. A molybdenite sample obtained from the main-ore stage vein, however, has a Re-Os age of 418.6 ± 1.8 Ma, which is slightly younger than the U-Pb age determinations of rutile. This indicates that the Re-Os isotope system was disturbed by the second (post-ore) thermal event related to ∼ 402 Ma quartz diorite porphyry. In line with published data, this study suggests that the rutile U-Pb age in combination with its REE patterns can be a powerful tool to trace the causative porphyry. Moreover, the typical LREE-enriched REE patterns coupled with the high Cu anomalies, inherited from the causative porphyry and related exsolving fluids, can be as diagnostic proxies for distinguishing the porphyry Cu-related hydrothermal rutile from those formed in orogenic gold deposits. Based on these two geochemical discriminators and U-Pb ages, rutile can serve as unique fingerprints to help improve porphyry copper exploration in green field or covered terranes to complement detrital zircon fertility indicators.
期刊介绍:
Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.