Relevant bibliographies by topics / Mid-Proterozoic

Academic literature on the topic 'Mid-Proterozoic'

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Published: 10 December 2022
Last updated: 30 January 2023

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Journal articles on the topic "Mid-Proterozoic"

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Hurley, Sarah J., Boswell A. Wing, Claire E. Jasper, Nicholas C. Hill, and Jeffrey C. Cameron. "Carbon isotope evidence for the global physiology of Proterozoic cyanobacteria." Science Advances 7, no. 2 (January 2021): eabc8998. http://dx.doi.org/10.1126/sciadv.abc8998.

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Ancestral cyanobacteria are assumed to be prominent primary producers after the Great Oxidation Event [≈2.4 to 2.0 billion years (Ga) ago], but carbon isotope fractionation by extant marine cyanobacteria (α-cyanobacteria) is inconsistent with isotopic records of carbon fixation by primary producers in the mid-Proterozoic eon (1.8 to 1.0 Ga ago). To resolve this disagreement, we quantified carbon isotope fractionation by a wild-type planktic β-cyanobacterium (Synechococcus sp. PCC 7002), an engineered Proterozoic analog lacking a CO2-concentrating mechanism, and cyanobacterial mats. At mid-Proterozoic pH and pCO2 values, carbon isotope fractionation by the wild-type β-cyanobacterium is fully consistent with the Proterozoic carbon isotope record, suggesting that cyanobacteria with CO2-concentrating mechanisms were apparently the major primary producers in the pelagic Proterozoic ocean, despite atmospheric CO2 levels up to 100 times modern. The selectively permeable microcompartments central to cyanobacterial CO2-concentrating mechanisms (“carboxysomes”) likely emerged to shield rubisco from O2 during the Great Oxidation Event.
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Slotznick, Sarah P., Samuel M. Webb, Joseph L. Kirschvink, and Woodward W. Fischer. "Mid‐Proterozoic Ferruginous Conditions Reflect Postdepositional Processes." Geophysical Research Letters 46, no. 6 (March 18, 2019): 3114–23. http://dx.doi.org/10.1029/2018gl081496.

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Derry, Louis A. "Causes and consequences of mid-Proterozoic anoxia." Geophysical Research Letters 42, no. 20 (October 24, 2015): 8538–46. http://dx.doi.org/10.1002/2015gl065333.

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Rast, N. "Mid-Proterozoic Supercontinent Rodinia: Its Basis and Extent." Gondwana Research 5, no. 1 (January 2002): 205. http://dx.doi.org/10.1016/s1342-937x(05)70903-5.

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Olson, Stephanie L., Christopher T. Reinhard, and Timothy W. Lyons. "Limited role for methane in the mid-Proterozoic greenhouse." Proceedings of the National Academy of Sciences 113, no. 41 (September 26, 2016): 11447–52. http://dx.doi.org/10.1073/pnas.1608549113.

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Pervasive anoxia in the subsurface ocean during the Proterozoic may have allowed large fluxes of biogenic CH4to the atmosphere, enhancing the climatic significance of CH4early in Earth’s history. Indeed, the assumption of elevatedpCH4during the Proterozoic underlies most models for both anomalous climatic stasis during the mid-Proterozoic and extreme climate perturbation during the Neoproterozoic; however, the geologic record cannot directly constrain atmospheric CH4levels and attendant radiative forcing. Here, we revisit the role of CH4in Earth’s climate system during Proterozoic time. We use an Earth system model to quantify CH4fluxes from the marine biosphere and to examine the capacity of biogenic CH4to compensate for the faint young Sun during the “boring billion” years before the emergence of metazoan life. Our calculations demonstrate that anaerobic oxidation of CH4coupled to SO42−reduction is a highly effective obstacle to CH4accumulation in the atmosphere, possibly limiting atmosphericpCH4to less than 10 ppm by volume for the second half of Earth history regardless of atmosphericpO2. If recentpO2constraints from Cr isotopes are correct, we predict that reduced UV shielding by O3should further limitpCH4to very low levels similar to those seen today. Thus, our model results likely limit the potential climate warming by CH4for the majority of Earth history—possibly reviving the faint young Sun paradox during Proterozoic time and challenging existing models for the initiation of low-latitude glaciation that depend on the oxidative collapse of a steady-state CH4greenhouse.
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Schieber, Jürgen. "Storm-dominated epicontinental clastic sedimentation in the Mid-Proterozoic Newland Formation, Montana, U.S.A." Neues Jahrbuch für Geologie und Paläontologie - Monatshefte 1987, no. 7 (July 1, 1987): 417–39. http://dx.doi.org/10.1127/njgpm/1987/1987/417.

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Corrigan, David, Nicholas G. Culshaw, and Jim K. Mortensen. "Pre-Grenvillian evolution and Grenvillian overprinting of the Parautochthonous Belt in Key Harbour, Ontario: U–Pb and field constraints." Canadian Journal of Earth Sciences 31, no. 3 (March 1, 1994): 583–96. http://dx.doi.org/10.1139/e94-051.

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The Parautochthonous Belt in the region of Key Harbour, Ontario, is composed of Early Proterozoic migmatitic para- and orthogneiss and Mid-Proterozoic granitoids, which were reworked during the Grenville orogeny. Grenvillian deformation is localized into anastomosing arrays of high-strain shear zones enclosing elongate bands and lozenges of rock subjected to lower and near-coaxial strain. Crosscutting relationships preserved in the low-strain domains document two pre-Grenvillian plutonic and tectonometamorphic events, which are bracketed in age by U–Pb zircon geochronology. A 1694 Ma leucogranite intrudes, and provides a minimum age for, high metamorphic grade gneisses formed during an earlier tectonometamorphic event (D1–M1). The leucogranite was intruded by mafic dykes, deformed, and metamorphosed at uppermost amphibolite facies during D2–M2, before the emplacement of Mid-Proterozoic granitoids at ca. 1450 Ma. Following the emplacement of gabbro dykes and pods at ca. 1238 Ma, the area was overprinted by granulite to uppermost amphibolite facies metamorphism (Grenvillian), for which monazites provide a minimum age of ca. 1035 Ma. Titanite U–Pb ages of 1003 – 1004 Ma record cooling through 600 °C. A regionally important swarm of east–west-trending posttectonic pegmatite dykes dated by U–Pb zircon at 990 Ma provides a minimum age for Grenvillian ductile deformation. The present data support the contention that the Parautochthonous Belt in the Key Harbour area consists in part of reworked midcontinental crust of Early to Mid-Proterozoic age.
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Wang, Haiyang, Chao Li, Meng Cheng, Zihu Zhang, and Thomas J. Algeo. "Redbed formation in the redox-stratified mid-Proterozoic ocean." Precambrian Research 379 (September 2022): 106815. http://dx.doi.org/10.1016/j.precamres.2022.106815.

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Gower, Charles F. "Mid-Proterozoic evolution of the eastern Grenville Province, Canada." Geologiska Föreningen i Stockholm Förhandlingar 112, no. 2 (June 1990): 127–39. http://dx.doi.org/10.1080/11035899009453170.

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JAVAUX, EMMANUELLE J., ANDREW H. KNOLL, and MALCOLM R. WALTER. "TEM evidence for eukaryotic diversity in mid-Proterozoic oceans." Geobiology 2, no. 3 (July 2004): 121–32. http://dx.doi.org/10.1111/j.1472-4677.2004.00027.x.

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Dissertations / Theses on the topic "Mid-Proterozoic"

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Wynn, Timothy James. "Proterozoic analogues of mid crustal deformation from NW Scotland and Namaqualand, South Africa." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320409.

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Booth, Peter William King. "Pan-African imprint on the early mid-proterozoic Richtersveld and Bushmanland sub-provinces near Eksteenfontein, Namaqualand, Republic of South Africa." Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/26232.

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The present investigation examines the relationship between the Proterozoic Richtersveld and Bushmanland Subprovinces in the westernmost part of the Namaqua Province, near Eksteenfontein, Republic of South Africa. There is a controversy about this relationship because isotopic data contrast with field evidence. On a regional scale the Richtersveld Subprovince is separated from the Bushmanland Subprovince by the northward-dipping Groothoek Thrust. North of the thrust the Richtersveld Subprovince is comprised of low grade volcano/ plutonic rocks of the Vioolsdrif Terrane and medium grade volcano sedimentary sequences of the Pella Terrane. Medium grade rocks of the Steinkopf Terrane (Bushmanland Subprovince) lie immediately south of the thrust. Late Proterozoic strata of the Stinkfontein Formation (Gariep Group) overlie the Namaqua Province in the west; Cambrian Nama Group outliers occur east of the Stinkfontein Formation. Isotopic data show that lithologies of the Richtersveld Subprovince formed between 2000 - 1730 Ma, whereas those of the Bushmanland Subprovince are younger. It is not clear whether the Namaqua metamorphic imprint (at 1200 - 1100 Ma), which is manifest in terranes south of the Groothoek Thrust, extended as far as the Vioolsdrif Terrane in the north. Early Proterozoic structural and metamorphic imprints are inferred to have been obliterated during this event. The westernmost part of the Namaqua Province was overprinted for a distance of 100 km from the coast, during the Pan-African event at 700 Ma and 500 Ma. An area measuring nearly 500 km2 , traversing the western extremity of the boundary between the Richtersveld and Bushmanland Subprovinces was mapped on a scale of 1:36,000. Field mapping was carried out with the aid of aerial photographs, whereas laboratory techniques included map compilation, structural analysis, X-ray diffractometry, geochemical (XRF) and electron microprobe analyses. Supracrustal units of the Richtersveld Subprovince are composed of quartzo-feldspathic gneisses, schists, and minor meta-pelites. Supracrustals of the Bushmanland Subprovince are less diverse than those of the Richtersveld Subprovince and have a disconformable relationship with them. Most intrusive rock-types are thick granitic sheets, except the Early Proterozoic Vioolsdrif Granodiorite which forms part of a batholithic pluton in the north. The Sabieboomrante adamellite gneiss, Kouefontein granite gneiss and Dabbieputs granite gneiss could not be correlated with lithologies commonly occurring in the Richtersveld and Bushmanland Subprovinces. They have been given the new rock names. Mafic and ultramafic rocks of the Klipbok complex occur along the strike of the Groothoek Thrust. They form part of the Richtersveld Subprovince.
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Briner, Andreas. "The anatomy of a late proterozoic continental margin at mid-crustal level: the crystalline basement of Salalah, Dhofar region, Sultanate of Oman /." [S.l.] : [s.n.], 1997. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Northrup, Clyde John. "Thermal, chemical, and structural characteristics of fluid migration and fluid-rock interaction in a mid-Proterozoic shear zone, Manzano Mountains, New Mexico." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/144646.

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The structure in the study area is dominated by a large, mid-Proterozoic shear zone that strikes NE and dips steeply SE. The zone had a NW directed tectonic transport direction during the shearing. Hydrothermal veining developed at several stages in the deformational history. Early fluids were relatively low in salinity and CO$\sb2$ content and flowed through the rock in small, pervasive structural sites produced by ductile deformation. Fluids migrating through the shear zone at progressively later times tended to be more focused along larger more brittle structures, and had higher salinity and CO$\sb2$ contents. The earliest veins show little alteration of the host rocks while progressively later veins show increasing amounts of wall rock alteration. Alteration near early veins is broadly characterized by increased Fe, Mg, Ca, and Al and decreased Si and K; later veins have increased Si and K, manifested by silicification, sericitization, +/$-$ sulfidization of the host rocks.
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Loveday, David C. "A proposed stratigraphic package for filling a mid-Proterozoic rift basin under the Bellefontaine Outlier area, Ohio, and the consequences of the rift on the formation of the Outlier /." Connect to resource, 2005. http://hdl.handle.net/1811/38972.

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Bendall, Betina. "Mid-Palaeozoic shear zones in the Strangways Range : a record of intracratonic tectonism in the Arunta Inlier, Central Australia." Title page, contents and introduction only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phb458.pdf.

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Toledo, G. E. "Chromium Isotope Constraints on the Mid-Proterozoic redox: evidence from δ53Cr of carbonates from the greater McArthur Basin, northern Australia." Thesis, 2018. https://hdl.handle.net/2440/133689.

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The Great Oxygenation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE) are interpreted to have made the most profound and permanent surface redox changes in Earth’s history. Changes in redox conditions between these two oxygenation events (i.e. mid-Proterozoic; 1.8-0.8 Ga) are poorly understood where environmental stability with persistently low atmospheric oxygen is assumed (<0.1% PAL; Present Atmospheric Levels). This period also witnessed the first appearance of primitive eukaryotes, however Eukarya diversification was determined to be effectively stagnant presumably due to sustained low atmospheric oxygen levels (pO2). More recent studies found evidence of relatively high mid-Proterozoic pO2, well in excess of 1% PAL, sufficient to promote diversification. The importance of better understanding the past redox conditions heightens due to the contrasting pO2 estimates that plausibly swayed the Eukarya diversification. This study presents stable Cr isotope (δ53Cr) values in mid-Proterozoic organic-rich carbonates of the Limbunya and McArthur Groups from the greater McArthur Basin. Analysed values from -0.293‰ to +1.389‰, present the oldest documented positively fractionated mid-Proterozoic δ53Cr values in marine carbonate units ca. 1.64 Gyrs ago, suggestive of a fluctuating, but increasing pO2 at the time of a generally reducing environment and supporting a permissive environment for Eukarya diversification. However, it is likely that its unstable nature probably inhibited wider and earlier Eukarya diversification, should pO2 levels truly be a barrier for evolution.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018
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Gueneli, Nur. "Late Mesoproterozoic Microbial Communities." Phd thesis, 2016. http://hdl.handle.net/1885/109340.

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The first eukaryotes are found in the geological record at ~1.6 Ga, a further 800 million years later they became more abundant and diverse, and only during the Ediacaran did they start shaping ecosystems. This work studies a marine and a lacustrine aquatic ecosystem at the edge of the Mesoproterozoic (~1.1 Ga) to gauge the role of eukaryotes and to investigate the environmental conditions that may have prohibited their proliferation. The evolutionary state of the earliest eukaryotic fossils remains unresolved. The first unambiguous stem group eukaryote appears at 1.2 Ga, but modern ferns occur around 0.8 Ga. Extreme bias on fossil preservation prevents estimation on how ecologically abundant early eukaryotes were. Here we use biomarkers to close this gap. They have low taxonomic resolution but afford a quantitative view of relative organism abundances. We combine biomarkers with inorganic, isotope geochemical and microscope analysis to investigate successions of the marine Taoudeni Basin and lacustrine Nonesuch Formation. Further, we include an analysis of the Cretaceous Maracaibo Basin to obtain a clear point of contrast from a period of time where redox environments were similar but eukaryotes were abundant. The extraordinary black shales of the Taoudeni Basin have high TOC (< 31 %), lack eukaryotic steranes despite present eukaryotic microfossils, contain aromatic steroids, and are mostly deposited under ferruginous and euxinic conditions. This implies at first sight a stagnant deep water environment. Yet, clear crinkly mats are preserved, invoking a non-uniformitarian ecosystem. Low atmospheric oxygen levels facilitate to explain clear, anoxic, shallow (<20 m) waters above phototrophic microbial mats. Biomarker data imply that the microbial community was composed of cyanobacteria, anoxygenic purple and green sulfur bacteria, and microaerophilic methanotrophs. It is likely that cyanobacteria switched between oxic and anoxic photosynthesis and dominated the photosynthetic community. The latter is supported by nitrogen isotopic composition of individual porphyrins, which range between 5.6 and 10.2 per mil and yield epsilon-porphyrin values of 0.5 to - 5.1 per mil. This study is the first unambiguous report of Mesoproterozoic geoporphyrins. The dominant species contain Ni and their structures relate to chl a, chl b/chl c3 and a chl c-like molecule. The biomarker and iron speciation results of Nonesuch shales qualitatively resemble the ones of the marine Taoudeni Basin including a mainly ferruginous depositional setting, absence of diagnostic eukaryotic biomarkers despite eukaryotic microfossils and biomarkers specific for cyanobacteria, anoxygenic purple and green sulfur bacteria, and microaerophilic methanotrophs. The bitumens of the Phanerozoic Maracaibo Basin were composed of degradation products of marine algae, green sulfur bacteria and archaea as well as terrestrial higher plants and lacustrine algae. The mixing of two components, marine and terrestrial organic matter, can explain the distribution of biomarkers. The data describe the restricted Maracaibo Basin as a stable, stratified sea influenced by upwelling waters near a shallow shelf. The results exemplify that biomarkers of primary producers such as algae are in fact preserved in similar environments as in the Mesoproterozoic and that the absence in ~1 Ga samples is not a preservation artefact.
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Van, Gool Jeroen Antonius Maria. "The Grenville front foreland fold-and-thrust belt in southwestern Labrador : mid-crustal structural and metamorphic configuration of a Proterozoic Orogenic thrust wedge /." 1992. http://collections.mun.ca/u?/theses,48444.

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Bendall, Betina. "Mid-Palaeozoic shear zones in the Strangways Range : a record of intracratonic tectonism in the Arunta Inlier, Central Australia / Betina Bendall." Thesis, 2000. http://hdl.handle.net/2440/19808.

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Books on the topic "Mid-Proterozoic"

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F, Gower Charles, Rivers Toby 1948-, Ryan Arthur Bruce 1951-, and Geological Association of Canada, eds. Mid-Proterozoic Laurentia-Baltica. St. John's, Nfld., Canada: Geological Association of Canada, Dept. of Earth Sciences, 1990.

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1951-, Ryan Arthur Bruce, Rivers Toby 1948-, Gower Charles F, and Geological Association of Canada, eds. Mid-proterozoic Laurentia-Baltica. St. John's, Nfld: Geological Association of Canada, 1990.

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Mid-Proterozoic Laurentia-Baltica. St. John's, Nfld: Geological Association of Canada, 1990.

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Book chapters on the topic "Mid-Proterozoic"

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Xueguang, Huang. "Mid-Late Proterozoic (Pre-Sinian) Crust." In Precambrian Crustal Evolution of China, 161–262. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-03697-6_4.

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Copper, Paul. "Evolution, Radiations, and Extinctions in Proterozoic to Mid-Paleozoic Reefs." In Topics in Geobiology, 89–119. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4615-1219-6_3.

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Haggerty, Stephen E. "Kimberlites, Supercontinents and Deep Earth Dynamics: Mid-Proterozoic India in Rodinia." In Topics in Igneous Petrology, 421–35. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-9600-5_16.

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Myers, John S. "Tectonic evolution of deep crustal structures in the mid-Proterozoic Albany-Fraser Orogen, Western Australia." In Evolution of Geological Structures in Micro- to Macro-scales, 473–85. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5870-1_26.

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Li, Z. X. "Tectonic history of the major East Asian lithospheric blocks since the mid-Proterozoic: A synthesis." In Mantle Dynamics and Plate Interactions in East Asia, 221–43. Washington, D. C.: American Geophysical Union, 1998. http://dx.doi.org/10.1029/gd027p0221.

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Hogan, John P., and M. Charles Gilbert. "The Southern Oklahoma Aulacogen: A Cambrian analog for Mid-Proterozoic AMCG (Anorthosite-Mangerite-Charnockite-Granite) complexes?" In Proceedings of the International Conferences on Basement Tectonics, 39–78. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5098-9_3.

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Schieber, Jürgen. "Sedimentary Structures: Textures and Depositional Settings of Shales from the Lower Belt Supergroup, Mid-Proterozoic, Montana, U.S.A." In Frontiers in Sedimentary Geology, 101–8. New York, NY: Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4612-4428-8_9.

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Nutman, A. P., T. Rivers, F. Longstaffe, and J. F. W. Park. "The Ataneq Fault and Mid-Proterozoic Retrograde Metamorphism of Early Archaean Tonalites of the Isukasia Area, Southern West Greenland: Reactions, Fluid Compositions and Implications for Regional Studies." In Fluid Movements — Element Transport and the Composition of the Deep Crust, 151–70. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0991-5_15.

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Goodwin, Alan M. "Mid-Proterozoic Crust." In Precambrian Geology, 359–450. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-12-289870-9.50009-6.

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Hollocher, Kurt, Peter Robinson, Maria Van Nostrand, and Emily Walsh. "The Blåhø Nappe, central Norwegian Scandinavian Caledonides: An oceanic arc–back-arc assemblage distinct from the Seve Nappe Complex." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2554(13).

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ABSTRACT The Scandinavian Caledonides have a complex latest Proterozoic–Early Devonian history, but they were finally assembled during the Silurian–Devonian (Scandian orogeny) collision between Baltica and Laurentia. Their dominant structural components are the Lower (Baltican margin), Middle (Baltican and farther outboard), Upper (Iapetan arcs), and Uppermost (Laurentian margin) Allochthons. This study examined the Blåhø Nappe, a complex unit of metamorphosed, intensely deformed igneous and sedimentary rocks assigned to the Middle Allochthon. Metamorphic grades are regionally amphibolite facies, but granulite- and eclogite-facies rocks are locally found. Although most metamorphic ages span a range from Middle Ordovician to Devonian, Blåhø eclogite and other high-pressure rock ages are exclusively Scandian. We analyzed 95 samples of Blåhø Nappe metamorphosed igneous rocks, which were mostly mafic rocks, composed of a minor arc-derived set and a major set transitional between arc and depleted to enriched mid-ocean-ridge basalt (MORB), a range characteristic of back-arc basins. Historically, the Blåhø Nappe has been assigned to the Seve Nappe Complex, the upper part of the Middle Allochthon as mapped in western Sweden and easternmost Norway. In contrast to the Blåhø Nappe, eclogites and other high-pressure rocks in the Seve Nappe Complex have yielded exclusively pre–Scandian orogeny Cambrian and Ordovician ages. Additionally, post–mid-Proterozoic igneous rocks of the Seve Nappe Complex are overwhelmingly dike swarms that were emplaced during the latest Proterozoic breakup of Rodinia, which have rift and MORB-type chemical signatures rather than arc and back-arc signatures, as has the Blåhø Nappe. We hypothesize that the Blåhø Nappe precursors formed on the upper plate, above a west-directed, late Cambrian to Ordovician subduction zone off the Baltican margin. Subduction of the Baltican margin, and possibly rifted fragments on the lower plate, produced the older Seve Nappe Complex eclogites and thrust the Blåhø and Seve Nappe Complex materials onto Baltica. This left the Blåhø Nappe and Seve Nappe Complex precursors on the lower plate during Scandian subduction and collision with Laurentia, allowing exclusively Scandian eclogite formation in the Blåhø Nappe. The Blåhø Nappe and Seve Nappe Complex thus seem to have distinct origins and should not be correlated with one another.
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Conference papers on the topic "Mid-Proterozoic"

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Planavsky, Noah J., Mingyu Zhao, and Christopher T. Reinhard. "MID-PROTEROZOIC OXYGEN AND METHANE." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-308114.

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Crowe, Sean A., Rachel L. Simister, Julia Maresca, and Steven Hallam. "MICROEUKARYOTES IN FERRUGINOUS (FE-RICH) MID-PROTEROZOIC OCEAN ANALOGUES." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-308307.

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Spencer, Christopher, Ross N. Mitchell, and Michael Brown. "SOME LIKE IT HOT: ENIGMATIC OROGENS OF THE MID-PROTEROZOIC." In GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-369115.

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Stueeken, Eva, Daniel Gregory, Indrani Mukherjee, and Peter McGoldrick. "EVIDENCE OF HYDROTHERMAL AMMONIUM VENTING INTO THE MID-PROTEROZOIC MCARTHUR BASIN." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-349686.

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Ji, Aoshuang, and James Kasting. "Controlling factors for atmospheric O2 during the mid-Proterozoic." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.10253.

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Subarkah, Darwinaji, Alan Collins, Juraj Farkas, Morgan Blades, Georgina Virgo, and Yuexiao Shao. "Reconstructing ancient palaeoenvironments from the Mid-Proterozoic packages of the greater McArthur Basin, Northern Australia." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.10706.

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Magnall, Joseph, Sarah Gleeson, Marcus Oelze, and Nicholas Hayward. "In situ pyrite chemistry from the mid-Proterozoic Barney Creek Formation and Teena Zn deposit." In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.6881.

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Liu, Peng, Jingjun Liu, Christopher T. Reinhard, Noah Planavsky, Dmitri Babikov, Kristie Boering, and James Kasting. "Mid-Proterozoic Atmospheric O2 Levels Re-calculated from D17O Values in Sulfates Using a Detailed 1-D Photochemical Model." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1599.

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Rämö, O. Tapani, James P. Calzia, and Virginia T. McLemore. "EVOLUTION OF SOUTHERN LAURENTIAN LITHOSPHERE; SOME NEW OBSERVATIONS FROM CRUSTAL DOMAINS AND MID-PROTEROZOIC ALKALINE MAGMATIC SUITES IN MOJAVIA AND MAZATZAL." In Joint 70th Annual Rocky Mountain GSA Section / 114th Annual Cordilleran GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018rm-314029.

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Frothingham, Michael G., Colin A. Shaw, and Chester A. Ruleman. "PROTEROZOIC STRUCTURAL RELATIONS WITHIN A THREE-PART SYSTEM OF DIKE INTRUSION, BATHOLITH EMPLACEMENT, AND SHEAR ZONE DEFORMATION AT MID-CRUSTAL DEPTHS NEAR LEADVILLE, COLORADO." In 68th Annual Rocky Mountain GSA Section Meeting. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016rm-276163.

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Reports on the topic "Mid-Proterozoic"

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Harris, L. B., P. Adiban, and E. Gloaguen. The role of enigmatic deep crustal and upper mantle structures on Au and magmatic Ni-Cu-PGE-Cr mineralization in the Superior Province. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328984.

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Abstract:
Aeromagnetic and ground gravity data for the Canadian Superior Province, filtered to extract long wavelength components and converted to pseudo-gravity, highlight deep, N-S trending regional-scale, rectilinear faults and margins to discrete, competent mafic or felsic granulite blocks (i.e. at high angles to most regional mapped structures and sub-province boundaries) with little to no surface expression that are spatially associated with lode ('orogenic') Au and Ni-Cu-PGE-Cr occurrences. Statistical and machine learning analysis of the Red Lake-Stormy Lake region in the W Superior Province confirms visual inspection for a greater correlation between Au deposits and these deep N-S structures than with mapped surface to upper crustal, generally E-W trending, faults and shear zones. Porphyry Au, Ni, Mo and U-Th showings are also located above these deep transverse faults. Several well defined concentric circular to elliptical structures identified in the Oxford Stull and Island Lake domains along the S boundary of the N Superior proto-craton, intersected by N- to NNW striking extensional fractures and/or faults that transect the W Superior Province, again with little to no direct surface or upper crustal expression, are spatially associated with magmatic Ni-Cu-PGE-Cr and related mineralization and Au occurrences. The McFaulds Lake greenstone belt, aka. 'Ring of Fire', constitutes only a small, crescent-shaped belt within one of these concentric features above which 2736-2733 Ma mafic-ultramafic intrusions bodies were intruded. The Big Trout Lake igneous complex that hosts Cr-Pt-Pd-Rh mineralization west of the Ring of Fire lies within a smaller concentrically ringed feature at depth and, near the Ontario-Manitoba border, the Lingman Lake Au deposit, numerous Au occurrences and minor Ni showings, are similarly located on concentric structures. Preliminary magnetotelluric (MT) interpretations suggest that these concentric structures appear to also have an expression in the subcontinental lithospheric mantle (SCLM) and that lithospheric mantle resistivity features trend N-S as well as E-W. With diameters between ca. 90 km to 185 km, elliptical structures are similar in size and internal geometry to coronae on Venus which geomorphological, radar, and gravity interpretations suggest formed above mantle upwellings. Emplacement of mafic-ultramafic bodies hosting Ni-Cr-PGE mineralization along these ringlike structures at their intersection with coeval deep transverse, ca. N-S faults (viz. phi structures), along with their location along the margin to the N Superior proto-craton, are consistent with secondary mantle upwellings portrayed in numerical models of a mantle plume beneath a craton with a deep lithospheric keel within a regional N-S compressional regime. Early, regional ca. N-S faults in the W Superior were reactivated as dilatational antithetic (secondary Riedel/R') sinistral shears during dextral transpression and as extensional fractures and/or normal faults during N-S shortening. The Kapuskasing structural zone or uplift likely represents Proterozoic reactivation of a similar deep transverse structure. Preservation of discrete faults in the deep crust beneath zones of distributed Neoarchean dextral transcurrent to transpressional shear zones in the present-day upper crust suggests a 'millefeuille' lithospheric strength profile, with competent SCLM, mid- to deep, and upper crustal layers. Mechanically strong deep crustal felsic and mafic granulite layers are attributed to dehydration and melt extraction. Intra-crustal decoupling along a ductile décollement in the W Superior led to the preservation of early-formed deep structures that acted as conduits for magma transport into the overlying crust and focussed hydrothermal fluid flow during regional deformation. Increase in the thickness of semi-brittle layers in the lower crust during regional metamorphism would result in an increase in fracturing and faulting in the lower crust, facilitating hydrothermal and carbonic fluid flow in pathways linking SCLM to the upper crust, a factor explaining the late timing for most orogenic Au. Results provide an important new dataset for regional prospectively mapping, especially with machine learning, and exploration targeting for Au and Ni-Cr-Cu-PGE mineralization. Results also furnish evidence for parautochthonous development of the S Superior Province during plume-related rifting and cannot be explained by conventional subduction and arc-accretion models.
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