C. Ishwar-Kumar, K. Sajeev, M. Satish‐Kumar, I. Williams, S. Wilde, T. Hokada, B. Windley
In this study we present field relations, petrology, whole-rock major, trace and rare earth element geochemistry, zircon U-Pb ages, whole-rock Sr and Nd isotopes, and in situ zircon Hf and O isotopes from the Karwar block, western peninsular India. The rocks consist predominantly of tonalite-trondhjemite-granodiorite (TTG), granite and amphibolite. The felsic rocks are grouped into three: 1. TTG-I characterised by low K2O, high Na2O and Al2O3, low Sr/Y and La/Yb ratios, slightly enriched HREEs, negative Sr, Eu and Ti anomalies, a 3.2 Ga crystallisation age, and 3.60 Ga and 3.47 Ga inherited zircons; 2. TTG-II with lower SiO2, higher Sr/Y and La/Yb ratios, stronger REE fractionation with no HREE enrichment, negative Nb and Ta anomalies, a 3.2 Ga crystallisation age, but no inheritance; 3. Granites with high SiO2 and K2O, low Na2O and Al2O3, very low Sr/Y and La/Yb ratios, weak REE fractionation with enriched REEs, negative Sr, Eu and Ti anomalies and a 2.94 Ga crystallisation age. The TTG-I formed from a mantle source, but with a significant component of older crustal material, whereas the TTG-II originated mostly from a mantle-derived juvenile magma. The granite evolved from an enriched source containing a relatively large amount of older crustal material. The precursors of TTG-I and -II are similar to mid-ocean ridge basalts (MORB), whereas the granites are similar to volcanic arc/within-plate sources and the amphibolites are remnants of gabbros/basalts. An initial 3.6 Ga crust likely formed by the underplating of an accreted oceanic plateau-like or island arc-like crust. TTG-I was produced by subduction and slab melting at a moderate depth, induced melting of mafic lower crust and older upper crust at 3.2 Ga. TTG-II formed at 3.2 Ga by subduction and with a higher degree of slab melting at a greater depth than TTG-1, together with more effective mixing with mantle peridotite, followed by intrusion and induced melting of mafic lower crust. Basaltic magmatism at 3.0 Ga and subsequent metamorphism to amphibolite resulted in extensive and thicker crust. Assimilation and melting of TTG crust at a shallow depth during the emplacement of a mantle-derived magma produced the 2.94 Ga granites. The presence of inherited zircons, combined with whole-rock major and trace elements, Nd isotopes and in situ zircon Hf and O isotopes, indicates that older crustal material was incorporated into the source magma of TTG-I and that the Karwar block originally contained 3.60 to 3.47 Ga crust that was subsequently reworked during the Paleo- and Mesoarchean.
{"title":"Paleo- to Mesoarchean crustal growth in the Karwar block, southern India: Constraints on TTG genesis and Archean tectonics","authors":"C. Ishwar-Kumar, K. Sajeev, M. Satish‐Kumar, I. Williams, S. Wilde, T. Hokada, B. Windley","doi":"10.2475/02.2022.02","DOIUrl":"https://doi.org/10.2475/02.2022.02","url":null,"abstract":"In this study we present field relations, petrology, whole-rock major, trace and rare earth element geochemistry, zircon U-Pb ages, whole-rock Sr and Nd isotopes, and in situ zircon Hf and O isotopes from the Karwar block, western peninsular India. The rocks consist predominantly of tonalite-trondhjemite-granodiorite (TTG), granite and amphibolite. The felsic rocks are grouped into three: 1. TTG-I characterised by low K2O, high Na2O and Al2O3, low Sr/Y and La/Yb ratios, slightly enriched HREEs, negative Sr, Eu and Ti anomalies, a 3.2 Ga crystallisation age, and 3.60 Ga and 3.47 Ga inherited zircons; 2. TTG-II with lower SiO2, higher Sr/Y and La/Yb ratios, stronger REE fractionation with no HREE enrichment, negative Nb and Ta anomalies, a 3.2 Ga crystallisation age, but no inheritance; 3. Granites with high SiO2 and K2O, low Na2O and Al2O3, very low Sr/Y and La/Yb ratios, weak REE fractionation with enriched REEs, negative Sr, Eu and Ti anomalies and a 2.94 Ga crystallisation age. The TTG-I formed from a mantle source, but with a significant component of older crustal material, whereas the TTG-II originated mostly from a mantle-derived juvenile magma. The granite evolved from an enriched source containing a relatively large amount of older crustal material. The precursors of TTG-I and -II are similar to mid-ocean ridge basalts (MORB), whereas the granites are similar to volcanic arc/within-plate sources and the amphibolites are remnants of gabbros/basalts. An initial 3.6 Ga crust likely formed by the underplating of an accreted oceanic plateau-like or island arc-like crust. TTG-I was produced by subduction and slab melting at a moderate depth, induced melting of mafic lower crust and older upper crust at 3.2 Ga. TTG-II formed at 3.2 Ga by subduction and with a higher degree of slab melting at a greater depth than TTG-1, together with more effective mixing with mantle peridotite, followed by intrusion and induced melting of mafic lower crust. Basaltic magmatism at 3.0 Ga and subsequent metamorphism to amphibolite resulted in extensive and thicker crust. Assimilation and melting of TTG crust at a shallow depth during the emplacement of a mantle-derived magma produced the 2.94 Ga granites. The presence of inherited zircons, combined with whole-rock major and trace elements, Nd isotopes and in situ zircon Hf and O isotopes, indicates that older crustal material was incorporated into the source magma of TTG-I and that the Karwar block originally contained 3.60 to 3.47 Ga crust that was subsequently reworked during the Paleo- and Mesoarchean.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"108 - 163"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41368151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liangbo Li, W. Xiao, B. Windley, He Yang, Xiaoliang Jia, Miao Sang, Nijiati Abuduxun, Yin Liu
Field, geochronological, geochemical and Sr-Nd isotopic analyses are applied to late Paleozoic gabbro-diorites and monzogranites in the Hulugou-Miaoergou regions, Harlik arc, in order to provide constraints on the tectonic evolution of the Eastern Tianshan orogen in the late Paleozoic. LA-ICP-MS zircon U-Pb ages show that the first pulse of gabbroic magmatism occurred at 348 ± 4 Ma, accompanied by simultaneous dioritic (342 ± 3 Ma) and monzogranitic (343 ± 5 Ma) magmatism, and the second pulse of gabbroic magmatism was at 334 ± 3 Ma. Most of the gabbros are medium- to high- K calc-alkaline in composition, and show enrichments in light rare earth elements (LREE) and large ion lithophile elements (LILE), but depletions in high field strength elements (HFSE, especially Nb and Ta). In combination with their juvenile isotopic signature (initial 87Sr/86Sr = 0.70345–0.70380, εNd(t) = 4.5–6), the geochemical features suggest that both pulses of gabbroic magmatism were likely derived from partial melting of asthenosphere facilitated by a flux from a subducting slab. The diorites also display the arc-related geochemical characteristics and juvenile isotopic signature (initial 87Sr/86Sr = 0.70355–0.70358, εNd(t) = 4.3–4.7), coupled with their intimate relationship with the gabbros indicate that they formed by fractional crystallization of clinopyroxene, plagioclase and amphibole from the first pulse of gabbroic magmatism. The monzogranites have relatively high A/CNK values (1.04–1.1) and are weakly to moderately peraluminous. Considering the presence of zircon xenocrysts dated at 510 to 450 Ma in the monzogranites, and their moderate molar Al2O3/(MgO+FeOT) and molar CaO/(MgO+FeOT) ratios, partial melting of supracrustal rocks of probable late Ordovician age was most likely the cause of their genesis and heterogeneity. These three different magmas (gabbroic, dioritic and monzogranitic) were probably extracted from a deep crustal hot zone. The primitive basaltic magmas continuously intruded the deep crust where they solidified, fractionated, assimilated, and heated the crust, generating in turn the peraluminous and A-type granitoids, similar to the magmas in the Lachlan orogen that intruded during progressive slab rollback. Based on all available evidence, we propose that southward slab rollback of the subducting Paleo-Asian Ocean in the early Carboniferous was responsible for the progressive emplacement of these different magmas, which eventually resulted in rifting of the Harlik arc.
{"title":"Early carboniferous rifting of the Harlik arc in the Eastern Tianshan (NW China): Response to rollback in the southern Altaids?","authors":"Liangbo Li, W. Xiao, B. Windley, He Yang, Xiaoliang Jia, Miao Sang, Nijiati Abuduxun, Yin Liu","doi":"10.2475/02.2022.07","DOIUrl":"https://doi.org/10.2475/02.2022.07","url":null,"abstract":"Field, geochronological, geochemical and Sr-Nd isotopic analyses are applied to late Paleozoic gabbro-diorites and monzogranites in the Hulugou-Miaoergou regions, Harlik arc, in order to provide constraints on the tectonic evolution of the Eastern Tianshan orogen in the late Paleozoic. LA-ICP-MS zircon U-Pb ages show that the first pulse of gabbroic magmatism occurred at 348 ± 4 Ma, accompanied by simultaneous dioritic (342 ± 3 Ma) and monzogranitic (343 ± 5 Ma) magmatism, and the second pulse of gabbroic magmatism was at 334 ± 3 Ma. Most of the gabbros are medium- to high- K calc-alkaline in composition, and show enrichments in light rare earth elements (LREE) and large ion lithophile elements (LILE), but depletions in high field strength elements (HFSE, especially Nb and Ta). In combination with their juvenile isotopic signature (initial 87Sr/86Sr = 0.70345–0.70380, εNd(t) = 4.5–6), the geochemical features suggest that both pulses of gabbroic magmatism were likely derived from partial melting of asthenosphere facilitated by a flux from a subducting slab. The diorites also display the arc-related geochemical characteristics and juvenile isotopic signature (initial 87Sr/86Sr = 0.70355–0.70358, εNd(t) = 4.3–4.7), coupled with their intimate relationship with the gabbros indicate that they formed by fractional crystallization of clinopyroxene, plagioclase and amphibole from the first pulse of gabbroic magmatism. The monzogranites have relatively high A/CNK values (1.04–1.1) and are weakly to moderately peraluminous. Considering the presence of zircon xenocrysts dated at 510 to 450 Ma in the monzogranites, and their moderate molar Al2O3/(MgO+FeOT) and molar CaO/(MgO+FeOT) ratios, partial melting of supracrustal rocks of probable late Ordovician age was most likely the cause of their genesis and heterogeneity. These three different magmas (gabbroic, dioritic and monzogranitic) were probably extracted from a deep crustal hot zone. The primitive basaltic magmas continuously intruded the deep crust where they solidified, fractionated, assimilated, and heated the crust, generating in turn the peraluminous and A-type granitoids, similar to the magmas in the Lachlan orogen that intruded during progressive slab rollback. Based on all available evidence, we propose that southward slab rollback of the subducting Paleo-Asian Ocean in the early Carboniferous was responsible for the progressive emplacement of these different magmas, which eventually resulted in rifting of the Harlik arc.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"313 - 350"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44976771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zaili Tao, Jiyuan Yin, W. Xiao, R. Seltmann, Wen Chen, M. Sun, Tao Wang, C. Yuan, S. Thomson, Yuelong Chen, X. Xia
Peraluminous granitoids have aluminum saturation indices (A/CNK) higher than 1.0, which overlap to some extent between S- and I-type granitoids. However, their source and petrogenesis are still disputed. For example, whole-rock compositions alone are not always a valid way to discriminate the sources of peraluminous granitoids. To identify the geochemical affinities, source and petrogenesis of the peraluminous granitoids, we present new geochemical data, in situ zircon U-Pb ages and Hf-O isotopic data, and whole-rock Sr-Nd isotopic data for the peraluminous granitoids in the South Tianshan Orogen Belt (STOB), Northwesten China. Zircon U-Pb ages suggest that these peraluminous granitoids were emplaced in the latest Carboniferous (ca. 299 Ma). They contain the diagnostic mineral muscovite and have high δ18OZrn values (>8.0 ‰) demonstrating a close affinity with S-type granitoids. Their low εNd(t) values (−5.3 to −7.6), combined with variable zircon εHf(t) values (−0.35 to −10.18), indicate that these S-type granitoids were likely derived from partial melting of metasedimentary rocks. In addition, inherited zircon cores from the S-type granitoids have variable δ18O values (6.34–10.5 ‰) and zircon εHf(t) values (−4.3 to +6.3), with age populations (ca. 400 to 500 Ma) similar to those of detrital zircons from late Carboniferous metasedimentary rocks in the region. These data show that the S-type granitoids were dominantly derived from late Carboniferous metasedimentary rocks rather than Precambrian crustal materials. The studied granitoids have a transitional composition between I- and S-type granitoids, which could be related to low compositional maturity of the late Carboniferous metasedimentary source. According to the spatial and temporal distribution and petrogenesis of the Carboniferous intrusive rocks in the STOB, we propose that a slab roll-back model can account for the generation of late Carboniferous S-type granitoids in the STOB.
{"title":"Contrasting styles of peraluminous S-type and I-type granitic magmatism: Identification and implications for the accretionary history of the Chinese South Tianshan","authors":"Zaili Tao, Jiyuan Yin, W. Xiao, R. Seltmann, Wen Chen, M. Sun, Tao Wang, C. Yuan, S. Thomson, Yuelong Chen, X. Xia","doi":"10.2475/02.2022.06","DOIUrl":"https://doi.org/10.2475/02.2022.06","url":null,"abstract":"Peraluminous granitoids have aluminum saturation indices (A/CNK) higher than 1.0, which overlap to some extent between S- and I-type granitoids. However, their source and petrogenesis are still disputed. For example, whole-rock compositions alone are not always a valid way to discriminate the sources of peraluminous granitoids. To identify the geochemical affinities, source and petrogenesis of the peraluminous granitoids, we present new geochemical data, in situ zircon U-Pb ages and Hf-O isotopic data, and whole-rock Sr-Nd isotopic data for the peraluminous granitoids in the South Tianshan Orogen Belt (STOB), Northwesten China. Zircon U-Pb ages suggest that these peraluminous granitoids were emplaced in the latest Carboniferous (ca. 299 Ma). They contain the diagnostic mineral muscovite and have high δ18OZrn values (>8.0 ‰) demonstrating a close affinity with S-type granitoids. Their low εNd(t) values (−5.3 to −7.6), combined with variable zircon εHf(t) values (−0.35 to −10.18), indicate that these S-type granitoids were likely derived from partial melting of metasedimentary rocks. In addition, inherited zircon cores from the S-type granitoids have variable δ18O values (6.34–10.5 ‰) and zircon εHf(t) values (−4.3 to +6.3), with age populations (ca. 400 to 500 Ma) similar to those of detrital zircons from late Carboniferous metasedimentary rocks in the region. These data show that the S-type granitoids were dominantly derived from late Carboniferous metasedimentary rocks rather than Precambrian crustal materials. The studied granitoids have a transitional composition between I- and S-type granitoids, which could be related to low compositional maturity of the late Carboniferous metasedimentary source. According to the spatial and temporal distribution and petrogenesis of the Carboniferous intrusive rocks in the STOB, we propose that a slab roll-back model can account for the generation of late Carboniferous S-type granitoids in the STOB.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"280 - 312"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45710910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W. Fu, H. Hou, R. Gao, Haiyan Wang, Lei Guo, Jianbo Zhou, Jin Yang, R. Guo, Zongdong Pan
The final closure of the Paleo-Asian Ocean (PAO) and its tectonic characteristics have been debated for several decades owing to a lack of high-resolution information on the lithosphere structure. Scholars have been attempting to explain deep tectonic evolutionary processes while studying continental growth at the southern margin of the Mongolian Terrane. In a bid to provide a new interpretation of the deep structure with a higher resolution, we study two reprocessed deep seismic reflection profiles. We studied the northern part (210 km long) of the 630-km-long deep seismic reflection profile extending across the North China Craton (NCC) margin to the northern Sino-Mongolia border in the west; and a parallel profile (80 km long) in the east near the Sino-Mongolia border. Both profiles are characterized by consistently north-dipping layered reflections projecting from the lower crust to the upper mantle, with an estimated thickness of 3.6 to 6 km between adjacent reflections beneath the Uliastai and Hegenshan belts. Arched reflections are observed in the middle and lower crust; these may have been caused by later magmatic activities. In addition, the Moho reflection is observed to be fairly continuous and flat in most parts of these two profiles. The layered lower crust reflections and mantle reflections serve as important evidence that northward subduction occurred during the closure of the Paleo-Asian Ocean at the southeastern margin of the Mongolian Terrane. We propose a detailed model of the evolutionary processes from the early Paleozoic to early Mesozoic. The proposed model explains how these deep reflections were formed.
{"title":"North-dipping relict subduction of the Paleo-Asian Ocean at the southeastern margin of the Mongolian Terrane: Study of two parallel deep seismic profiles","authors":"W. Fu, H. Hou, R. Gao, Haiyan Wang, Lei Guo, Jianbo Zhou, Jin Yang, R. Guo, Zongdong Pan","doi":"10.2475/02.2022.09","DOIUrl":"https://doi.org/10.2475/02.2022.09","url":null,"abstract":"The final closure of the Paleo-Asian Ocean (PAO) and its tectonic characteristics have been debated for several decades owing to a lack of high-resolution information on the lithosphere structure. Scholars have been attempting to explain deep tectonic evolutionary processes while studying continental growth at the southern margin of the Mongolian Terrane. In a bid to provide a new interpretation of the deep structure with a higher resolution, we study two reprocessed deep seismic reflection profiles. We studied the northern part (210 km long) of the 630-km-long deep seismic reflection profile extending across the North China Craton (NCC) margin to the northern Sino-Mongolia border in the west; and a parallel profile (80 km long) in the east near the Sino-Mongolia border. Both profiles are characterized by consistently north-dipping layered reflections projecting from the lower crust to the upper mantle, with an estimated thickness of 3.6 to 6 km between adjacent reflections beneath the Uliastai and Hegenshan belts. Arched reflections are observed in the middle and lower crust; these may have been caused by later magmatic activities. In addition, the Moho reflection is observed to be fairly continuous and flat in most parts of these two profiles. The layered lower crust reflections and mantle reflections serve as important evidence that northward subduction occurred during the closure of the Paleo-Asian Ocean at the southeastern margin of the Mongolian Terrane. We propose a detailed model of the evolutionary processes from the early Paleozoic to early Mesozoic. The proposed model explains how these deep reflections were formed.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"380 - 395"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43550411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Wilde, Shoujie Liu, Y. Rojas‐Agramonte, Guochun Zhao
It is now over eleven years' ago, in November 2010, that the American Journal of Science published the first of two volumes marking the 70 birthday of Alfred Kroner. We, his friends and colleagues, planned to mark Alfred's 80 birthday with another special issue of the American Journal of Science, designed to showcase the scientific advances that had been made over the past decade in those areas of geoscientific endeavor that were closest to Alfred's heart. Sadly, Alfred passed away on 22 May 2019, less than four months before his 80 birthday (8 September). This is the third and final volume compiled to celebrate his tremendous contribution to geoscientific research. In the Preface to American Journal of Science, volume 310, number 9 of November 2010, a comprehensive outline of Alfred's career up until that date was presented (kindly outlined and supplemented by Alfred) and the reader is referred to this for more details of his earlier career. In the Preface to the first of these special issues (volume 321, numbers 1,2 of January-February 2021), we focused on the last ten years, outlining Alfred's major contributions, where his work was principally focused, and the key activities he undertook. We include this information below: Alfred's long association with Prof Liu Dunyi and the Beijing SHRIMP Center continued throughout the last decade of his life and resulted in a fruitful cooperation that was especially beneficial to young Chinese geoscientists. Alfred would spend several months every year based at the SHRIMP Laboratory, although he made many journeys both within China to deliver invited lectures and short courses at numerous institutions and universities, as well as undertaking many fieldtrips both in China and neighboring countries. In particular, his work on the Central Asian Orogenic Belt (CAOB) was ongoing in Mongolia, Kyrgyzstan and Russia. As Chairman of the International Precambrian Research Center of China (IPRCC), Alfred also organized a series of lectures, workshops and fieldtrips every year; many designed principally for students. The first of these was in May 2010, when the field workshop “Early Crustal Evolution of the SE Kaapvaal Craton in South Africa and Swaziland” was organized and attended by a large contingent from China. In October that year, the 5 SHRIMP Workshop and a workshop on “Advances in high-resolution SIMS and LA-ICP-MS Geochronology and Application to Geological Processes” were held in Beijing and Alfred took an active part in their organization. These were followed by a field excursion to Inner Mongolia to investigate Paleoproterozoic ultra-high temperature rocks of the Khondalite Belt. Also organized during this period was a training course in zircon geochronology including SHRIMP analytical techniques, which was run for the benefit of higher degree students from universities and institutions all over China. This course was presented by Ian Williams, Robert Pidgeon, Lutz Nasdala, William Griffin, Fernando Corf
{"title":"THIS IS THE THIRD ISSUE DEDICATED TO THE MEMORY OF DISTINGUISHED SCIENTIST ALFRED KRONER WHO SADLY PASSED AWAY ON 22 MAY 2019","authors":"S. Wilde, Shoujie Liu, Y. Rojas‐Agramonte, Guochun Zhao","doi":"10.2475/02.2022.11","DOIUrl":"https://doi.org/10.2475/02.2022.11","url":null,"abstract":"It is now over eleven years' ago, in November 2010, that the American Journal of Science published the first of two volumes marking the 70 birthday of Alfred Kroner. We, his friends and colleagues, planned to mark Alfred's 80 birthday with another special issue of the American Journal of Science, designed to showcase the scientific advances that had been made over the past decade in those areas of geoscientific endeavor that were closest to Alfred's heart. Sadly, Alfred passed away on 22 May 2019, less than four months before his 80 birthday (8 September). This is the third and final volume compiled to celebrate his tremendous contribution to geoscientific research. In the Preface to American Journal of Science, volume 310, number 9 of November 2010, a comprehensive outline of Alfred's career up until that date was presented (kindly outlined and supplemented by Alfred) and the reader is referred to this for more details of his earlier career. In the Preface to the first of these special issues (volume 321, numbers 1,2 of January-February 2021), we focused on the last ten years, outlining Alfred's major contributions, where his work was principally focused, and the key activities he undertook. We include this information below: Alfred's long association with Prof Liu Dunyi and the Beijing SHRIMP Center continued throughout the last decade of his life and resulted in a fruitful cooperation that was especially beneficial to young Chinese geoscientists. Alfred would spend several months every year based at the SHRIMP Laboratory, although he made many journeys both within China to deliver invited lectures and short courses at numerous institutions and universities, as well as undertaking many fieldtrips both in China and neighboring countries. In particular, his work on the Central Asian Orogenic Belt (CAOB) was ongoing in Mongolia, Kyrgyzstan and Russia. As Chairman of the International Precambrian Research Center of China (IPRCC), Alfred also organized a series of lectures, workshops and fieldtrips every year; many designed principally for students. The first of these was in May 2010, when the field workshop “Early Crustal Evolution of the SE Kaapvaal Craton in South Africa and Swaziland” was organized and attended by a large contingent from China. In October that year, the 5 SHRIMP Workshop and a workshop on “Advances in high-resolution SIMS and LA-ICP-MS Geochronology and Application to Geological Processes” were held in Beijing and Alfred took an active part in their organization. These were followed by a field excursion to Inner Mongolia to investigate Paleoproterozoic ultra-high temperature rocks of the Khondalite Belt. Also organized during this period was a training course in zircon geochronology including SHRIMP analytical techniques, which was run for the benefit of higher degree students from universities and institutions all over China. This course was presented by Ian Williams, Robert Pidgeon, Lutz Nasdala, William Griffin, Fernando Corf","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"vii - xi"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48861780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the past two decades, extensive investigations have been carried out on the Trans-North China Orogen (TNCO), a Himalayan-type continental collisional belt along which the Eastern Block and the Western Block amalgamated to form the basement of the North China Craton. There are now coherent outlines of the timing and tectonic processes involved in the Paleoproterozoic amalgamation of the TNCO. However, pre-collisional tectonic setting and driving mechanism of the TNCO still remain controversial. To resolve these issues, we carried out field petrological and geochemical investigations on the Tianzhen gneisses from the Huai'an Complex in the TNCO. The Tianzhen gneisses consist predominantly of tonalitic-trondhjemitic-granodioritic (TTG) series, which can be further divided into low-Yb and high-Yb types. Our results indicate that although both low-Yb and high-Yb TTG series were formed in a magmatic arc environment, their petrogenetic origins were different. The Huai'an low-Yb TTG magma was derived from the partial melting of subducted oceanic crust consisting of eclogite or 30% garnet-bearing amphibolite under 15 to 20 kbar or even higher pressure, with garnet, amphibole, and rutile as residues. In contrast, the high-Yb TTG magma was derived from the partial melting of subducted oceanic slab consisting of garnet-free or 7% garnet amphibolite under 10 to 15 kbar, leaving residual garnet and amphibole. Both magmas then interacted with the overlying mantle wedge during ascent. Thus, it can be concluded that the Tianzhen TTG magmas were derived from the partial melting of subducted oceanic crust and interaction with mantle peridotite, supporting a magmatic arc setting for the Huai'an Complex during Neoarchean to Paleoproterozoic time. Associated with other analogous gneiss complexes in the TNCO, a long-lived Neoarchean to Paleoproterozoic magmatic arc system is established in the Trans-North China Orogen.
{"title":"A Neoarchean to Paleoproterozoic magmatic arc in the Trans-North China Orogen: Petrological and geochemical constraints from the Tianzhen gneisses in the Huai'an Complex","authors":"Dingyi Zhao, M. Sun","doi":"10.2475/02.2022.03","DOIUrl":"https://doi.org/10.2475/02.2022.03","url":null,"abstract":"In the past two decades, extensive investigations have been carried out on the Trans-North China Orogen (TNCO), a Himalayan-type continental collisional belt along which the Eastern Block and the Western Block amalgamated to form the basement of the North China Craton. There are now coherent outlines of the timing and tectonic processes involved in the Paleoproterozoic amalgamation of the TNCO. However, pre-collisional tectonic setting and driving mechanism of the TNCO still remain controversial. To resolve these issues, we carried out field petrological and geochemical investigations on the Tianzhen gneisses from the Huai'an Complex in the TNCO. The Tianzhen gneisses consist predominantly of tonalitic-trondhjemitic-granodioritic (TTG) series, which can be further divided into low-Yb and high-Yb types. Our results indicate that although both low-Yb and high-Yb TTG series were formed in a magmatic arc environment, their petrogenetic origins were different. The Huai'an low-Yb TTG magma was derived from the partial melting of subducted oceanic crust consisting of eclogite or 30% garnet-bearing amphibolite under 15 to 20 kbar or even higher pressure, with garnet, amphibole, and rutile as residues. In contrast, the high-Yb TTG magma was derived from the partial melting of subducted oceanic slab consisting of garnet-free or 7% garnet amphibolite under 10 to 15 kbar, leaving residual garnet and amphibole. Both magmas then interacted with the overlying mantle wedge during ascent. Thus, it can be concluded that the Tianzhen TTG magmas were derived from the partial melting of subducted oceanic crust and interaction with mantle peridotite, supporting a magmatic arc setting for the Huai'an Complex during Neoarchean to Paleoproterozoic time. Associated with other analogous gneiss complexes in the TNCO, a long-lived Neoarchean to Paleoproterozoic magmatic arc system is established in the Trans-North China Orogen.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"164 - 189"},"PeriodicalIF":2.9,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46466092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Rugenstein, K. Methner, T. Kukla, A. Mulch, Tina Lüdecke, J. Fiebig, A. Meltzer, K. Wegmann, P. Zeitler, C. Chamberlain
The timing of surface uplift of the Altai Mountains in northern Central Asia—and the climatic consequences—remains controversial. Today, the Altai Mountains cast a substantial rain shadow, effectively separating the western Gobi Desert and steppe from the Siberian Taiga. We take advantage of this stark climatic gradient to trace the interaction of climate and topography in the lee of the Altai. First, we present new water stable isotope data that demonstrate that—along with this climatic gradient—the Altai modify the δ18O of precipitation via rainout on the leeward side of the range. Second, we present a new paleosol carbonate clumped isotope (Δ47) record that spans much of the Neogene from the immediate lee of the Altai in western Mongolia to address how surface temperatures may have responded to potential uplift during the Neogene. We find that Δ47-derived temperatures have, overall, declined by approximately 7 °C over the course of the Neogene, though the precise timing of this decrease remains uncertain. Third, we pair our Δ47 record with previously published stable isotope data to demonstrate that the timing of decreasing temperatures corresponds with long-term stability in paleosol carbonate δ13C values. In contrast, increases in paleosol carbonate δ13C values—linked to declining vegetation productivity—are correlated with intervals of increasing temperatures. We speculate that declines in vegetation biomass and leaf area changed the partitioning of latent and sensible heat, resulting in rising surface temperatures during Altai uplift. In contrast, long-term Neogene cooling drove the overall decline in surface temperatures. Reconstructed soil water δ18O values (based on carbonate δ18O and Δ47 values) remain surprisingly stable over our Neogene record, differing from our expectation of decreasing δ18O values due to progressive uplift of the Altai Mountains and Neogene cooling. We demonstrate that the shift in precipitation seasonality that likely accompanied Altai uplift obscured any change in lee-side precipitation δ18O that would be expected from surface elevation change alone.
{"title":"Clumped isotope constraints on warming and precipitation seasonality in Mongolia following Altai uplift","authors":"J. Rugenstein, K. Methner, T. Kukla, A. Mulch, Tina Lüdecke, J. Fiebig, A. Meltzer, K. Wegmann, P. Zeitler, C. Chamberlain","doi":"10.2475/01.2022.02","DOIUrl":"https://doi.org/10.2475/01.2022.02","url":null,"abstract":"The timing of surface uplift of the Altai Mountains in northern Central Asia—and the climatic consequences—remains controversial. Today, the Altai Mountains cast a substantial rain shadow, effectively separating the western Gobi Desert and steppe from the Siberian Taiga. We take advantage of this stark climatic gradient to trace the interaction of climate and topography in the lee of the Altai. First, we present new water stable isotope data that demonstrate that—along with this climatic gradient—the Altai modify the δ18O of precipitation via rainout on the leeward side of the range. Second, we present a new paleosol carbonate clumped isotope (Δ47) record that spans much of the Neogene from the immediate lee of the Altai in western Mongolia to address how surface temperatures may have responded to potential uplift during the Neogene. We find that Δ47-derived temperatures have, overall, declined by approximately 7 °C over the course of the Neogene, though the precise timing of this decrease remains uncertain. Third, we pair our Δ47 record with previously published stable isotope data to demonstrate that the timing of decreasing temperatures corresponds with long-term stability in paleosol carbonate δ13C values. In contrast, increases in paleosol carbonate δ13C values—linked to declining vegetation productivity—are correlated with intervals of increasing temperatures. We speculate that declines in vegetation biomass and leaf area changed the partitioning of latent and sensible heat, resulting in rising surface temperatures during Altai uplift. In contrast, long-term Neogene cooling drove the overall decline in surface temperatures. Reconstructed soil water δ18O values (based on carbonate δ18O and Δ47 values) remain surprisingly stable over our Neogene record, differing from our expectation of decreasing δ18O values due to progressive uplift of the Altai Mountains and Neogene cooling. We demonstrate that the shift in precipitation seasonality that likely accompanied Altai uplift obscured any change in lee-side precipitation δ18O that would be expected from surface elevation change alone.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"28 - 54"},"PeriodicalIF":2.9,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47096565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Masterson, M. Alperin, G. L. Arnold, W. Berelson, B. Jørgensen, H. Røy, D. Johnston
Measurement of the multiple sulfur isotopes (32S/33S/34S) enables the calibration of microbial biosignatures and provides a unique diagnosis of S-based metabolic processes: sulfate reduction, disproportionation, and sulfide oxidation. All three metabolisms carry distinct geochemical consequences for S cycling in modern systems, and are particularly powerful for paleoenvironmental interpretations if their respective contributions can be separated. To hone those interpretations and to further develop a quantitative context for understanding early diagenetic sulfur cycling, we constructed a multiple S isotope reactive transport model for the sediments of a geochemically well-characterized system (Aarhus Bay, Denmark). The model reconciles pore water and solid phase concentration profiles of the major species associated with Fe/S/C cycling, and uses multiple S isotope systematics to predict the isotope profiles of the major S species, including pore water sulfate, free sulfide and solid phase pyrite. We note that very large fractionations associated with sulfate reduction (34εsr = 70‰) are required to reproduce the observed pore water profiles, and we reconcile these fractionations with low temperature theoretical predictions for isotope equilibrium fractionation. The minor sulfur isotope values (noted as Δ33S) of sulfate increase at shallow depths within the Aarhus Bay core, and decrease when sulfate drops below 10 mM. Values (Δ33S) for sulfide decrease nearly monotonically towards seawater sulfate values near the zone of sulfate depletion. Pyrite Δ33S values are nearly uniform downcore (0.170 ± 0.010‰) despite a ∼10‰ enrichment in surface versus deep pyrite δ34S values. Sulfate reduction is the most important process controlling S isotope pore water distributions, with modest contributions from oxidative S cycling. Further, microbial sulfate reduction demonstrates large fractionations typically not expected for shallow, organic rich (TOC ∼ 4%) continental margin systems.
{"title":"Understanding the isotopic composition of sedimentary sulfide: A multiple sulfur isotope diagenetic model for Aarhus Bay","authors":"A. Masterson, M. Alperin, G. L. Arnold, W. Berelson, B. Jørgensen, H. Røy, D. Johnston","doi":"10.2475/01.2022.01","DOIUrl":"https://doi.org/10.2475/01.2022.01","url":null,"abstract":"Measurement of the multiple sulfur isotopes (32S/33S/34S) enables the calibration of microbial biosignatures and provides a unique diagnosis of S-based metabolic processes: sulfate reduction, disproportionation, and sulfide oxidation. All three metabolisms carry distinct geochemical consequences for S cycling in modern systems, and are particularly powerful for paleoenvironmental interpretations if their respective contributions can be separated. To hone those interpretations and to further develop a quantitative context for understanding early diagenetic sulfur cycling, we constructed a multiple S isotope reactive transport model for the sediments of a geochemically well-characterized system (Aarhus Bay, Denmark). The model reconciles pore water and solid phase concentration profiles of the major species associated with Fe/S/C cycling, and uses multiple S isotope systematics to predict the isotope profiles of the major S species, including pore water sulfate, free sulfide and solid phase pyrite. We note that very large fractionations associated with sulfate reduction (34εsr = 70‰) are required to reproduce the observed pore water profiles, and we reconcile these fractionations with low temperature theoretical predictions for isotope equilibrium fractionation. The minor sulfur isotope values (noted as Δ33S) of sulfate increase at shallow depths within the Aarhus Bay core, and decrease when sulfate drops below 10 mM. Values (Δ33S) for sulfide decrease nearly monotonically towards seawater sulfate values near the zone of sulfate depletion. Pyrite Δ33S values are nearly uniform downcore (0.170 ± 0.010‰) despite a ∼10‰ enrichment in surface versus deep pyrite δ34S values. Sulfate reduction is the most important process controlling S isotope pore water distributions, with modest contributions from oxidative S cycling. Further, microbial sulfate reduction demonstrates large fractionations typically not expected for shallow, organic rich (TOC ∼ 4%) continental margin systems.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"1 - 27"},"PeriodicalIF":2.9,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41927697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The analogy between Al8/3O4 – MgAl2O4 spinels and AgSbS2 − PbS galenas is explored. Although the spinel observed in calcium-aluminum-rich inclusions in carbonaceous chondrites (CAIs) is nearly pure MgAl2O4 and the galena found in hydrothermal ore deposits is nearly pure PbS, in both occurrences a very strong case may sometimes be made that these phases originally crystallized as solid solutions with substantially higher abundance of these minor components, Al8/3O4 in CAI spinel and AgSbS2 in hydrothermal galena. It is shown that a few retrograde net-transport reactions accompanying Al8/3O4 breakdown in Al8/3O4 − MgAl2O4 spinels can account for several important features of spinel-rich CAIs including reverse zoning of åkermanite−gehlenite melilites, the production of Al-rich diopside and the depletion of anorthite in reaction rims, and the scarcity of grossite despite its previous presence as a high temperature condensate. AgSbS2 in galena is analogous, because galenas in ore deposits today have an undetectable amount of AgSbS2 (for example, Knowles,1983), yet, for example, the galena-rich ore deposits from the Coeur d'Alene mining district (ID) were responsible for the largest recorded number of ounces of Ag produced in the world until recently. Accordingly, it is appropriate that the primary Al8/3O4 contents of spinels in CAIs are reconstructed following methods analogous to those employed by Sack and others (2002,2005) to reconstruct the primary AgSbS2 contents of galenas from the Coeur d'Alene ores, if CAIs spinels are to be used to constrain temperatures, and hence pressures, of canonical condensation. Several examples are given to demonstrate the thermal constraints which may be obtained from reconstructed primary spinel Al8/3O4 concentrations starting with the Al8/3O4 -rich CAI spinels reported by Yurimoto and others (2021) and El Goresy and others (1984). The compositions of spinels which form rims around corundum and corundum-hibonite aggregates in CAIs from the Murchison and Murray chondrites (Makide and others,2013) are then used to prove that Al8/3O4 in Al8/3O4 − MgAl2O4 spinels from CAIs are completely analogous to AgSbS2 in AgSbS2 − PbS galenas from hydrothermal ore deposits.
{"title":"Temperatures of canonical condensation: Constraints from CAIs","authors":"R. Sack","doi":"10.2475/01.2022.03","DOIUrl":"https://doi.org/10.2475/01.2022.03","url":null,"abstract":"The analogy between Al8/3O4 – MgAl2O4 spinels and AgSbS2 − PbS galenas is explored. Although the spinel observed in calcium-aluminum-rich inclusions in carbonaceous chondrites (CAIs) is nearly pure MgAl2O4 and the galena found in hydrothermal ore deposits is nearly pure PbS, in both occurrences a very strong case may sometimes be made that these phases originally crystallized as solid solutions with substantially higher abundance of these minor components, Al8/3O4 in CAI spinel and AgSbS2 in hydrothermal galena. It is shown that a few retrograde net-transport reactions accompanying Al8/3O4 breakdown in Al8/3O4 − MgAl2O4 spinels can account for several important features of spinel-rich CAIs including reverse zoning of åkermanite−gehlenite melilites, the production of Al-rich diopside and the depletion of anorthite in reaction rims, and the scarcity of grossite despite its previous presence as a high temperature condensate. AgSbS2 in galena is analogous, because galenas in ore deposits today have an undetectable amount of AgSbS2 (for example, Knowles,1983), yet, for example, the galena-rich ore deposits from the Coeur d'Alene mining district (ID) were responsible for the largest recorded number of ounces of Ag produced in the world until recently. Accordingly, it is appropriate that the primary Al8/3O4 contents of spinels in CAIs are reconstructed following methods analogous to those employed by Sack and others (2002,2005) to reconstruct the primary AgSbS2 contents of galenas from the Coeur d'Alene ores, if CAIs spinels are to be used to constrain temperatures, and hence pressures, of canonical condensation. Several examples are given to demonstrate the thermal constraints which may be obtained from reconstructed primary spinel Al8/3O4 concentrations starting with the Al8/3O4 -rich CAI spinels reported by Yurimoto and others (2021) and El Goresy and others (1984). The compositions of spinels which form rims around corundum and corundum-hibonite aggregates in CAIs from the Murchison and Murray chondrites (Makide and others,2013) are then used to prove that Al8/3O4 in Al8/3O4 − MgAl2O4 spinels from CAIs are completely analogous to AgSbS2 in AgSbS2 − PbS galenas from hydrothermal ore deposits.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":"322 1","pages":"55 - 63"},"PeriodicalIF":2.9,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42811580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ayman E. Maurice, M. Azer, P. Asimow, Fawzy F. Basta, H. Helmy, T. Shibata
Two small, isolated ultramafic masses in the northeastern part of the Wadi Kid area, southeast Sinai, are composed of variably serpentinized harzburgite and lherzolite with minor talc-anthophyllite rock. The primary phases are dominantly olivine, orthopyroxene and Cr-spinel; clinopyroxene, amphibole, and phlogopite are also found in lherzolite samples. The whole-rock Mg# of harzburgite samples (89–91) is higher than that of lherzolite (average 82). The harzburgite samples contain olivine with higher Mg and Ni contents, orthopyroxene with higher Mg#, and Cr-spinel with higher Cr content than do the lherzolite samples. The REE patterns of clinopyroxene and amphibole in lherzolite are most consistent with a cumulate origin. Although several compositional characteristics of the harzburgites resemble those of residual mantle, in detail the Cr2O3 and Al2O3 contents of fresh Cr-spinel in harzburgite are different from those found in mantle samples or in any of the Neoproterozoic ophiolitic peridotites throughout the Arabian-Nubian Shield. Thus, all the ultramafic rocks at Kabr El-Bonaya are best explained as ultramafic cumulates, with harzburgite consisting of early-formed cumulate phases and lherzolite containing later-formed cumulate phases with higher REE abundances, primary hydrous minerals, evolved primary silicates, and high TiO2 (0.77 wt.%) and Al2O3 (18 wt.%) contents in Cr-spinel. The trace-element characteristics of the rocks indicate a subduction-related parental magma: whole-rock chondrite-normalized REE patterns are LREE-enriched; calculated fO2 values are elevated (+2.47 to +3.39 log units above the fayalite-magnetite-quartz buffer); and computed N-MORB-normalized trace element patterns for melts in equilibrium with clinopyroxene and amphibole have negative Nb-Ta anomalies and enrichment in large-ion lithophile elements. The low Al2O3/SiO2 ratios (0.007–0.040) of harzburgite samples and the low TiO2 contents and high Cr# of their Cr-spinel indicate derivation from a mantle source that experienced high-degree partial melting. From these characteristics, we infer a boninitic parental melt for the harzburgite. We offer an illustrative quantitative fractionation model that can explain the successive derivation of harzburgite and lherzolite cumulates along a single equilibrium, polybaric cooling path. We conclude that the Kabr El-Bonaya ultramafic cumulates represent the exposed roots of a Neoproterozoic island arc that was caught in the collision between East and West Gondwana.
西奈半岛东南部Wadi Kid地区东北部的两个小型孤立超镁铁质岩体由可变蛇纹石化的方辉橄榄岩和二辉橄榄岩以及少量滑石花千枚岩组成。原生相主要为橄榄石、斜方辉石和铬尖晶石；斜辉石、角闪石和金云母也存在于二辉橄榄岩样品中。方辉橄榄岩样品的全岩Mg#（89–91）高于二辉橄榄岩（平均82）。方辉橄榄岩样品含有Mg和Ni含量较高的橄榄石、Mg#含量较高的斜方辉石和Cr含量较高的Cr尖晶石。二辉橄榄岩中单斜辉石和角闪石的REE模式与堆积成因最为一致。尽管方辉橄榄岩的几个组成特征与残余地幔的组成特征相似，但详细而言，方辉橄榄石中新鲜铬尖晶石的Cr2O3和Al2O3含量与整个阿拉伯-努比亚地盾的地幔样品或任何新元古代蛇绿橄榄岩中发现的含量不同。因此，Kabr El Bonaya的所有超镁铁质岩石最好被解释为超镁铁质堆积体，方辉橄榄岩由早期形成的堆积相组成，二辉橄榄岩包含后期形成的具有较高REE丰度的堆积相、原生含水矿物、演化的原生硅酸盐和高TiO2（0.77 wt.%）和Al2O3（18 wt.%）含量。岩石的微量元素特征表明其母岩浆与俯冲有关：全岩球粒陨石归一化REE模式为LREE富集；计算出的fO2值升高（高于辉长岩-磁铁矿-石英缓冲液+2.47至+3.39 log单位）；与斜辉石和角闪石平衡的熔体的计算的N-MORB归一化微量元素模式具有负Nb-Ta异常和大离子亲石元素富集。方辉橄榄岩样品的低Al2O3/SiO2比（0.007–0.040）及其铬尖晶石的低TiO2含量和高Cr#表明其来源于经历了高度部分熔融的地幔源。根据这些特征，我们推断出方辉橄榄岩的玻碳母熔体。我们提供了一个说明性的定量分馏模型，可以解释方辉橄榄岩和二辉橄榄岩沿着单一平衡、多气压冷却路径堆积的连续推导。我们得出的结论是，Kabr El Bonaya超镁铁质堆积体代表了在东西冈瓦纳大陆碰撞中被捕获的新元古代岛弧的裸露根部。
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