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Tang M, Liu X, Chen K. High Mg# of the continental crust explained by calc-alkaline differentiation. Natl Sci Rev 2023; 10:nwac258. [PMID: 36875781 PMCID: PMC9976743 DOI: 10.1093/nsr/nwac258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 11/10/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022] Open
Abstract
We used compiled geochemical data to investigate the mechanisms that control Mg# (molar ratio of Mg/(Mg + FeT)) in andesitic arc lavas. We find that andesites from mature continental arcs with crustal thickness of >45 km have systematically higher Mg# than those from oceanic arcs with crustal thickness of <30 km. The elevated Mg# in continental arc lavas results from strong Fe depletion during high-pressure differentiation favored in thick crusts. This proposal is reinforced by our compiled melting/crystallization experiment data. We show that the Mg# characteristics of continental arc lavas match that of the continental crust. These findings suggest that the formation of many high-Mg# andesites and the continental crust may not require slab-melt/peridotite interactions. Instead, the high Mg# of the continental crust can be explained by intracrustal calc-alkaline differentiation processes in magmatic orogens.
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Affiliation(s)
- Ming Tang
- Key Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; School of Earth and Space Sciences, Peking University, Beijing 100871, China
| | - Xuanyu Liu
- Key Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education; School of Earth and Space Sciences, Peking University, Beijing 100871, China
| | - Kang Chen
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
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Basalt derived from highly refractory mantle sources during early Izu-Bonin-Mariana arc development. Nat Commun 2021; 12:1723. [PMID: 33741949 PMCID: PMC7979767 DOI: 10.1038/s41467-021-21980-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 02/19/2021] [Indexed: 12/03/2022] Open
Abstract
The magmatic character of early subduction zone and arc development is unlike mature systems. Low-Ti-K tholeiitic basalts and boninites dominate the early Izu-Bonin-Mariana (IBM) system. Basalts recovered from the Amami Sankaku Basin (ASB), underlying and located west of the IBM’s oldest remnant arc, erupted at ~49 Ma. This was 3 million years after subduction inception (51-52 Ma) represented by forearc basalt (FAB), at the tipping point between FAB-boninite and typical arc magmatism. We show ASB basalts are low-Ti-K, aluminous spinel-bearing tholeiites, distinct compared to mid-ocean ridge (MOR), backarc basin, island arc or ocean island basalts. Their upper mantle source was hot, reduced, refractory peridotite, indicating prior melt extraction. ASB basalts transferred rapidly from pressures (~0.7-2 GPa) at the plagioclase-spinel peridotite facies boundary to the surface. Vestiges of a polybaric-polythermal mineralogy are preserved in this basalt, and were not obliterated during persistent recharge-mix-tap-fractionate regimes typical of MOR or mature arcs. Magmatism associated with early growth of subduction zones is unlike that of mature island arc systems. Here, the authors find basalts with distinct mineralogical and geochemical characteristics were erupted during this early stage, and derived from extremely refractory, hot mantle sources.
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Williams HM, Matthews S, Rizo H, Shorttle O. Iron isotopes trace primordial magma ocean cumulates melting in Earth's upper mantle. SCIENCE ADVANCES 2021; 7:7/11/eabc7394. [PMID: 33712459 PMCID: PMC7954453 DOI: 10.1126/sciadv.abc7394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
The differentiation of Earth ~4.5 billion years (Ga) ago is believed to have culminated in magma ocean crystallization, crystal-liquid separation, and the formation of mineralogically distinct mantle reservoirs. However, the magma ocean model remains difficult to validate because of the scarcity of geochemical tracers of lower mantle mineralogy. The Fe isotope compositions (δ57Fe) of ancient mafic rocks can be used to reconstruct the mineralogy of their mantle source regions. We present Fe isotope data for 3.7-Ga metabasalts from the Isua Supracrustal Belt (Greenland). The δ57Fe signatures of these samples extend to values elevated relative to modern equivalents and define strong correlations with fluid-immobile trace elements and tungsten isotope anomalies (μ182W). Phase equilibria models demonstrate that these features can be explained by melting of a magma ocean cumulate component in the upper mantle. Similar processes may operate today, as evidenced by the δ57Fe and μ182W heterogeneity of modern oceanic basalts.
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Affiliation(s)
- Helen M Williams
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK.
| | - Simon Matthews
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK
| | - Hanika Rizo
- Department of Earth Sciences, Carleton University, Ottawa, ON, Canada
| | - Oliver Shorttle
- Department of Earth Sciences, The University of Cambridge, Cambridge, UK
- Institute of Astronomy, The University of Cambridge, Cambridge, UK
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Richter M, Nebel O, Schwindinger M, Nebel-Jacobsen Y, Dick HJB. Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas. Sci Rep 2021; 11:4123. [PMID: 33603040 PMCID: PMC7893168 DOI: 10.1038/s41598-021-83387-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 01/11/2021] [Indexed: 11/24/2022] Open
Abstract
Two-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe = + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.
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Affiliation(s)
- Marianne Richter
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia.
| | - Oliver Nebel
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Martin Schwindinger
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Yona Nebel-Jacobsen
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, 3800, Australia
| | - Henry J B Dick
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543-1539, USA
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Richter M, Nebel O, Maas R, Mather B, Nebel-Jacobsen Y, Capitanio FA, Dick HJB, Cawood PA. An Early Cretaceous subduction-modified mantle underneath the ultraslow spreading Gakkel Ridge, Arctic Ocean. SCIENCE ADVANCES 2020; 6:6/44/eabb4340. [PMID: 33127673 PMCID: PMC7608816 DOI: 10.1126/sciadv.abb4340] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Earth's upper mantle, as sampled by mid-ocean ridge basalts (MORBs) at oceanic spreading centers, has developed chemical and isotopic heterogeneity over billions of years through focused melt extraction and re-enrichment by recycled crustal components. Chemical and isotopic heterogeneity of MORB is dwarfed by the large compositional spectrum of lavas at convergent margins, identifying subduction zones as the major site for crustal recycling into and modification of the mantle. The fate of subduction-modified mantle and if this heterogeneity transmits into MORB chemistry remains elusive. Here, we investigate the origin of upper mantle chemical heterogeneity underneath the Western Gakkel Ridge region in the Arctic Ocean through MORB geochemistry and tectonic plate reconstruction. We find that seafloor lavas from the Western Gakkel Ridge region mirror geochemical signatures of an Early Cretaceous, paleo-subduction zone, and conclude that the upper mantle can preserve a long-lived, stationary geochemical memory of past geodynamic processes.
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Affiliation(s)
- Marianne Richter
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia.
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
| | - Oliver Nebel
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
| | - Roland Maas
- School of Earth Sciences, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Ben Mather
- School of Geosciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Yona Nebel-Jacobsen
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
| | - Fabio A Capitanio
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
| | - Henry J B Dick
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1539, USA
| | - Peter A Cawood
- Isotopia Laboratory, School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
- School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia
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Lissenberg CJ, MacLeod CJ, Bennett EN. Consequences of a crystal mush-dominated magma plumbing system: a mid-ocean ridge perspective. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20180014. [PMID: 30966931 PMCID: PMC6335481 DOI: 10.1098/rsta.2018.0014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/16/2018] [Indexed: 06/02/2023]
Abstract
Crystal mush is rapidly emerging as a new paradigm for the evolution of igneous systems. Mid-ocean ridges provide a unique opportunity to study mush processes: geophysical data indicate that, even at the most magmatically robust fast-spreading ridges, the magma plumbing system typically comprises crystal mush. In this paper, we describe some of the consequences of crystal mush for the evolution of the mid-ocean ridge magmatic system. One of these is that melt migration by porous flow plays an important role, in addition to rapid, channelized flow. Facilitated by both buoyancy and (deformation-enhanced) compaction, porous flow leads to reactions between the mush and migrating melts. Reactions between melt and the surrounding crystal framework are also likely to occur upon emplacement of primitive melts into the mush. Furthermore, replenishment facilitates mixing between the replenishing melt and interstitial melts of the mush. Hence, crystal mushes facilitate reaction and mixing, which leads to significant homogenization, and which may account for the geochemical systematics of mid-ocean ridge basalt (MORB). A second consequence is cryptic fractionation. At mid-ocean ridges, a plagioclase framework may already have formed when clinopyroxene saturates. As a result, clinopyroxene phenocrysts are rare, despite the fact that the vast majority of MORB records clinopyroxene fractionation. Hence, melts extracted from crystal mush may show a cryptic fractionation signature. Another consequence of a mush-dominated plumbing system is that channelized flow of melts through the crystal mush leads to the occurrence of vertical magmatic fabrics in oceanic gabbros, as well as the entrainment of diverse populations of phenocrysts. Overall, we conclude that the occurrence of crystal mush has a number of fundamental implications for the behaviour and evolution of magmatic systems, and that mid-ocean ridges can serve as a useful template for trans-crustal mush columns elsewhere. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'.
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Affiliation(s)
- C. Johan Lissenberg
- School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, UK
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Reekie CDJ, Jenner FE, Smythe DJ, Hauri EH, Bullock ES, Williams HM. Sulfide resorption during crustal ascent and degassing of oceanic plateau basalts. Nat Commun 2019; 10:82. [PMID: 30622301 PMCID: PMC6325133 DOI: 10.1038/s41467-018-08001-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 12/09/2018] [Indexed: 11/30/2022] Open
Abstract
Mantle plume-related magmas typically have higher chalcophile and siderophile element (CSE) contents than mid-ocean ridge basalts (MORB). These differences are often attributed to sulfide-under-saturation of plume-related melts. However, because of eruption-related degassing of sulfur (S) and the compositional, pressure, temperature and redox effects on S-solubility, understanding the magmatic behavior of S is challenging. Using CSE data for oceanic plateau basalts (OPB), which rarely degas S, we show that many OPB are sulfide-saturated. Differences in the timing of sulfide-saturation between individual OPB suites can be explained by pressure effects on sulfur solubility associated with ascent through over-thickened crust. Importantly, where S-degassing does occur, OPB have higher CSE contents than S-undegassed melts at similar stages of differentiation. This can be explained by resorption of earlier-formed sulfides, which might play an important role in enriching degassed melts in sulfide-compatible CSE and potentially contributes to anomalous enrichments of CSE in the crust.
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Affiliation(s)
- C D J Reekie
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
| | - F E Jenner
- School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - D J Smythe
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK
| | - E H Hauri
- Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, Washington, DC, 20015, USA
| | - E S Bullock
- Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, Washington, DC, 20015, USA
| | - H M Williams
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK
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Hartley ME, Bali E, Maclennan J, Neave DA, Halldórsson SA. Melt inclusion constraints on petrogenesis of the 2014-2015 Holuhraun eruption, Iceland. CONTRIBUTIONS TO MINERALOGY AND PETROLOGY. BEITRAGE ZUR MINERALOGIE UND PETROLOGIE 2018; 173:10. [PMID: 31983759 PMCID: PMC6953965 DOI: 10.1007/s00410-017-1435-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Accepted: 12/20/2017] [Indexed: 06/02/2023]
Abstract
The 2014-2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine-plagioclase-augite-melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1 ± 0.7 kbar (7.5 ± 2.5 km), which is in agreement with the depths of earthquakes (6 ± 1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1-12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H2O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12-0.29 m s-1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.
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Affiliation(s)
- Margaret E. Hartley
- School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
| | - Enikö Bali
- Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland
| | - John Maclennan
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - David A. Neave
- Institut für Mineralogie, Leibniz Universität Hannover, Hannover, Germany
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Yu X, Chen LH, Zeng G. Growing magma chambers control the distribution of small-scale flood basalts. Sci Rep 2015; 5:16824. [PMID: 26581905 PMCID: PMC4652174 DOI: 10.1038/srep16824] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/20/2015] [Indexed: 11/09/2022] Open
Abstract
Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar-Ar and K-Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2 > 47.5 wt.%) from Xinchang-Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4-3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40-0.66; TiO2/MgO = 0.23-0.35) during about 6 Myr (9.4-3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3-3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60-1.28; TiO2/MgO = 0.30-0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment-magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts.
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Affiliation(s)
- Xun Yu
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
| | - Li-Hui Chen
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
| | - Gang Zeng
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
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Primitive layered gabbros from fast-spreading lower oceanic crust. Nature 2013; 505:204-7. [PMID: 24291793 DOI: 10.1038/nature12778] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 10/10/2013] [Indexed: 11/08/2022]
Abstract
Three-quarters of the oceanic crust formed at fast-spreading ridges is composed of plutonic rocks whose mineral assemblages, textures and compositions record the history of melt transport and crystallization between the mantle and the sea floor. Despite the importance of these rocks, sampling them in situ is extremely challenging owing to the overlying dykes and lavas. This means that models for understanding the formation of the lower crust are based largely on geophysical studies and ancient analogues (ophiolites) that did not form at typical mid-ocean ridges. Here we describe cored intervals of primitive, modally layered gabbroic rocks from the lower plutonic crust formed at a fast-spreading ridge, sampled by the Integrated Ocean Drilling Program at the Hess Deep rift. Centimetre-scale, modally layered rocks, some of which have a strong layering-parallel foliation, confirm a long-held belief that such rocks are a key constituent of the lower oceanic crust formed at fast-spreading ridges. Geochemical analysis of these primitive lower plutonic rocks--in combination with previous geochemical data for shallow-level plutonic rocks, sheeted dykes and lavas--provides the most completely constrained estimate of the bulk composition of fast-spreading oceanic crust so far. Simple crystallization models using this bulk crustal composition as the parental melt accurately predict the bulk composition of both the lavas and the plutonic rocks. However, the recovered plutonic rocks show early crystallization of orthopyroxene, which is not predicted by current models of melt extraction from the mantle and mid-ocean-ridge basalt differentiation. The simplest explanation of this observation is that compositionally diverse melts are extracted from the mantle and partly crystallize before mixing to produce the more homogeneous magmas that erupt.
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