Geology Pub Date : 2024-02-06 DOI: 10.1130/g51796.1

Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang

{"title":"Intersection between tectonic faults and magmatic systems promotes swarms with large-magnitude earthquakes around the Tengchong volcanic field, southeastern Tibetan Plateau","authors":"Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang","doi":"10.1130/g51796.1","DOIUrl":"https://doi.org/10.1130/g51796.1","url":null,"abstract":"Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139800576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions 前寒武纪至更新世褐辉石熔融包裹体的 40Ar/39Ar 测定时间

Geology Pub Date : 2024-02-06 DOI: 10.1130/g51777.1

B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas

{"title":"Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions","authors":"B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas","doi":"10.1130/g51777.1","DOIUrl":"https://doi.org/10.1130/g51777.1","url":null,"abstract":"Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139860297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions 前寒武纪至更新世褐辉石熔融包裹体的 40Ar/39Ar 测定时间

Geology Pub Date : 2024-02-06 DOI: 10.1130/g51777.1

B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas

{"title":"Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions","authors":"B. Jicha, A. Schaen, Bryan Wathen, William O. Nachlas","doi":"10.1130/g51777.1","DOIUrl":"https://doi.org/10.1130/g51777.1","url":null,"abstract":"Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139800308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Intersection between tectonic faults and magmatic systems promotes swarms with large-magnitude earthquakes around the Tengchong volcanic field, southeastern Tibetan Plateau 构造断层与岩浆系统的交汇促进了青藏高原东南部腾冲火山区周围的大震群发生

Geology Pub Date : 2024-02-06 DOI: 10.1130/g51796.1

Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang

{"title":"Intersection between tectonic faults and magmatic systems promotes swarms with large-magnitude earthquakes around the Tengchong volcanic field, southeastern Tibetan Plateau","authors":"Min Liu, Yen Joe Tan, Xinglin Lei, Hongyi Li, Yunpeng Zhang, Weitao Wang","doi":"10.1130/g51796.1","DOIUrl":"https://doi.org/10.1130/g51796.1","url":null,"abstract":"Volcanic regions commonly host swarms comprising small to moderate-sized earthquakes while tectonic faults host mostly mainshock-aftershock sequences that can include very large earthquakes. In the southeastern Tibetan Plateau, large tectonic faults formed by the collision between the Indian and Eurasian plates intersect with the intraplate Tengchong volcanic field, and the seismic behavior of such an environment remains unclear. Here, we built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field and found that (1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; (2) all swarms contained fluid-diffusion-like migration fronts, with some occurring where high CO2 emissions have been detected; and (3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139860551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Iron fertilization–induced deoxygenation of eastern equatorial Pacific Ocean intermediate waters during the Paleocene–Eocene thermal maximum 古新世-始新世热量最大期铁肥化诱发的东赤道太平洋中间水域脱氧现象

Geology Pub Date : 2024-02-05 DOI: 10.1130/g51770.1

Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu

引用次数: 0

Iron fertilization–induced deoxygenation of eastern equatorial Pacific Ocean intermediate waters during the Paleocene–Eocene thermal maximum 古新世-始新世热量最大期铁肥化诱发的东赤道太平洋中间水域脱氧现象

Geology Pub Date : 2024-02-05 DOI: 10.1130/g51770.1

Xiaodong Jiang, Xiangyu Zhao, Xiaoming Sun, Andrew P. Roberts, A. Sluijs, Yu‐Min Chou, Weiqi Yao, Jieqi Xing, Weijie Zhang, Qingsong Liu

引用次数: 0

Nannofossil imprints across the Paleocene-Eocene thermal maximum 古新世-始新世热量最大期的化石印记

Geology Pub Date : 2024-02-02 DOI: 10.1130/g51746.1

S. Slater, Paul R. Bown, Phillip E. Jardine

{"title":"Nannofossil imprints across the Paleocene-Eocene thermal maximum","authors":"S. Slater, Paul R. Bown, Phillip E. Jardine","doi":"10.1130/g51746.1","DOIUrl":"https://doi.org/10.1130/g51746.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139809360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Does zircon geochemistry record global sediment subduction? 锆石地球化学是否记录了全球沉积物俯冲？

Geology Pub Date : 2024-02-02 DOI: 10.1130/g51817.1

K. Sundell, F. A. Macdonald, Stephen J. Puetz

{"title":"Does zircon geochemistry record global sediment subduction?","authors":"K. Sundell, F. A. Macdonald, Stephen J. Puetz","doi":"10.1130/g51817.1","DOIUrl":"https://doi.org/10.1130/g51817.1","url":null,"abstract":"Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139869425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Does zircon geochemistry record global sediment subduction? 锆石地球化学是否记录了全球沉积物俯冲？

Geology Pub Date : 2024-02-02 DOI: 10.1130/g51817.1

K. Sundell, F. A. Macdonald, Stephen J. Puetz

{"title":"Does zircon geochemistry record global sediment subduction?","authors":"K. Sundell, F. A. Macdonald, Stephen J. Puetz","doi":"10.1130/g51817.1","DOIUrl":"https://doi.org/10.1130/g51817.1","url":null,"abstract":"Global compilations of zircon geochemistry have been used as evidence for changes in plate tectonic styles and surface environments. In particular, zircon δ18O has been used as a proxy for global sediment subduction and incorporation into igneous melts. However, research employing such compilations commonly ignores geologic and geographic context. We analyze a newly georeferenced zircon δ18O database from 1000 Ma to present. The compilation shows positive and negative isotopic excursions, both of which have been interpreted in the context of global phenomena. Sensitivity testing demonstrates that these excursions are the product of regional tectonic environments. Specifically, low Tonian–Cryogenian δ18O, previously interpreted as a climate signal of snowball Earth glacial meltwater, is isolated to ultra-high-pressure rocks of the Dabie Sulu orogen in central Asia, ophiolites in Egypt, and juvenile arc development in Madagascar, predating Cryogenian glaciation. Positive anomalies in the Ediacaran–Cambrian and Devonian, previously interpreted to record snowball Earth erosion and the rise of land plants, are the result of upper-plate, supracrustal sources of Gondwana. A Neogene anomaly is the result of volcanic rocks associated with Yellowstone and Iceland. Sampling bias in zircon geochemical compilations is analogous to that of Lagerstätten (sites of exquisite fossil preservation) and the “monograph effect” (large contributions from individual researchers) in paleontology, which both result in artifacts of over-representation. Long-term zircon δ18O trends broadly track the generation of collisional granites and continental arcs through time, recording the melting of sediments and sedimentary rocks in individual orogens, and not variations in sediment subduction globally.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139809744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Nannofossil imprints across the Paleocene-Eocene thermal maximum 古新世-始新世热量最大期的化石印记

Geology Pub Date : 2024-02-02 DOI: 10.1130/g51746.1

S. Slater, Paul R. Bown, Phillip E. Jardine

{"title":"Nannofossil imprints across the Paleocene-Eocene thermal maximum","authors":"S. Slater, Paul R. Bown, Phillip E. Jardine","doi":"10.1130/g51746.1","DOIUrl":"https://doi.org/10.1130/g51746.1","url":null,"abstract":"The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139869030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

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