The Bolnisi district is a distinct tectonic zone of the Lesser Caucasus, which is considered to represent the eastern extremity of the Turkish Eastern Pontides. Late Cretaceous, low-K, calc-alkaline ...to high-K rhyolite of the Mashavera and Gasandami Suites is the predominant rock type of the district, and is accompanied by subsidiary dacite, and rare high-alumina basalt and trachyandesite of the Tandzia Suite. The Mashavera and Gasandami rhyolite and dacite have yielded U-Pb LA-ICP-MS and TIMS zircon ages between 87.14 ± 0.16 and 81.64 ± 0.94 Ma, which are in line with the Coniacan-Santonian ages of radiolarian fauna of the Mashavera Suite. The felsic rocks of the Mashavera and Gasandami Suites were deposited during a ~6.6 m.y.-long silicic magmatic flare-up event, which together with the Tandzia Suite mafic rocks, documents Late Cretaceous bimodal magmatism in an extensional tectonic setting. Trace element data indicate that high Y-Zr, low- to high-silica rhyolite and dacite, and low Y-Zr high-silica rhyolite have been erupted, respectively, from coeval deep and shallow crustal reservoirs. The rocks of the bimodal magmatic event are overlain by high-K volcanic rocks of the Campanian Shorsholeti Suite, which have been erupted during slab roll-back and steepening, from magmas produced by deep melting of a metasomatised mantle. Eocene postcollisional felsic intrusions crosscut the Late Cretaceous rock.
The Coniacian to early Campanian bimodal magmatism, and the subsequent high-K magmatism of the Bolnisi district are contemporaneous and share geochemical characteristics with the Late Cretaceous magmatism of the Eastern Pontides. It documents the existence of a Late Cretaceous regional silicic magmatic province, and subsequent high-K magmatism during slab steepening. This regional magmatic evolution coincided with the opening of the Black Sea and the Adjara-Trialeti basins. This evolution was coeval with the wanning stages of northern Neotethyan subduction, after a ~40 m.y.-long magmatic lull along the southern Eurasian convergent margin. Early Eocene adakite-like magmatism affected both the Bolnisi district and the Eastern Pontides, demonstrating a common postcollisional magmatic evolution.
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•Late Cretaceous subduction-related silicic magmatic flare-up, north Lesser Caucasus.•Bimodal magmatism in Lesser Caucasus-Eastern Pontides coeval with Black Sea opening.•High-K magmatism and slab steepening during final northern Neotethys subduction.•Early Eocene postcollisional adakite-like magmatism of the northern Lesser Caucasus.
•This study documents two episodes of Paleoproterozoic mafic intrusive suites from the NCC.•The Haicheng suite comes from newly metasomatized lithospheric mantle.•The Guohua suite originates from a ...cratonic sub-continental lithospheric mantle.•Two suites witnessed a tectonic shift in from continental arc to post-orogenic regime.
Mafic dyke swarms constitute a common occurrence within the cratonic provinces in the world since the Archean–Proterozoic boundary and their geneses harbor critical information for facilitating regional tectonic and supercontinental reconstruction. This zircon U–Pb dating and geochemical study documents two episodes of Paleoproterozoic mafic intrusions from Liaoning province, North China Craton (NCC): the Haicheng suite (HCS) with an emplacement age of ca. 2125 Ma from the Liaodong Peninsula and the Guohua suite (GHS) with an age of ca. 1816 Ma from the western Liaoning terrane. The HCS meta-gabbros are tholeiitic in composition with an SiO2 range from 46 to 52%, modest enrichment in light rare earth elements (LREE) and depletion in high field strength elements (HFSE), and possess radiogenic whole-rock Nd (ɛNd(t)=+1.91 to +4.21) and zircon Hf (ɛHf(t)=+4.02 to +8.48) isotopic compositions. These features endow the HCS with a juvenile subduction fluid-metasomatized lithospheric mantle source. By contrast, the GHS exhibits a meta-gabbroic to -dioritic composition and a transitional character from tholeiitic to calc-alkali, with variably enriched LREEs and more evolved isotopic signatures (ɛNd(t)=−0.20 to −5.82, zircon ɛHf(t)=+0.09 to +4.91) than the HCS. While the relatively intact high-Fe gabbroic samples are supposed to represent partial melts from a fertile cratonic sub-continental lithospheric mantle source in the garnet±spinel stability field, the low-Fe dioritic ones tend to bear the imprints of subsequent assimilation and fractional crystallization process. Apart from making an important contribution to the present archive of the Paleoproterozoic mafic dyke swarms in the NCC, the present two mafic magmatic suites witnessed a shift in tectonic setting from a subduction-related continental arc environment to a post-orogenic extensional regime. Synthesizing two suites with coeval felsic igneous episodes as well as concomitant episodic metamorphic events in the Jiao-Liao-Ji belt leads to the characterization of a possible divergent double subduction system in the eastern NCC during the time span of ca. 2.2–1.80 Ga. Synchronized beating of episodic magmatic and metamorphic pulses in the constituent mobile belts of the NCC carries further implication of attesting to the ubiquity and importance of divergent double subduction system in the cratonic amalgamation and its incorporation within the supercontinent Columbia.
The petrogenesis of continental crust from its ultimate mantle source can be reconstructed from the element abundances and radiogenic isotope compositions of ideally pristine igneous rocks. The ...initial isotope compositions of igneous rocks provide geochemical constraints on the age, composition and evolution of their source(s). Determining initial isotope ratios for rock samples can be challenging, especially in rocks with a long and protracted thermal history. The Rb-Sr system is highly sensitive to parent-daughter element fractionation during magma differentiation. This makes the Rb-Sr isotope systematics ideal to trace the precursor composition of Archean felsic crust and constrain the time of element fractionation during the formation and subsequent modification of continental crust. Initial isotope compositions can be obtained directly from minerals that strongly prefer the daughter element and effectively exclude the parent element of the radio-isotope system of interest. Apatite, having a near zero Rb/Sr ratio, is ideal for preserving its initial 87Sr/86Sr and zircon records initial 176Hf/177Hf compositions. Combined modelling of Sr and Hf isotope data from granitoids of the Archean Singhbhum Craton, indicates that the older Paleoarchean granitoids, emplaced between 3.53 Ga and 3.44 Ga, were derived from a mafic precursor (∼52–54 wt% SiO2) sourced from a depleted mantle at ∼3.71 Ga. Initial 87Sr/86Sr isotope signatures of matrix apatite and apatite inclusions in zircon from the younger Paleoarchean granitoids (3.4–3.2 Ga) of the Singhbhum Craton indicate these younger granitoids were produced by mixing of magma generated from an older mafic source and partial melts derived from the older granitoids. The combined Sr-Hf isotope modelling links the timing of mantle extraction of the precursor material for Paleoarchean Singhbhum granitoids with a known mafic crust extraction event at ∼3.71 Ga. In combination, the new Sr isotope data from apatite combined with whole rock and zircon Hf isotope data from the literature reveal a ∼1 Ga protracted crustal growth and differentiation history of the nucleus of the Singhbhum Craton. By combining radio-isotope systems like 87Rb-87Sr and 176Lu-176Hf, the petrogenesis of Archean felsic crust from the extraction of mafic material from the mantle to reworking in an orogenic cycle to emplacement can be reconstructed. This approach can be applied to other greenstone-gneiss terranes to quantify the spatio-temporal and compositional evolution of voluminous felsic crust and the formation of cratons in the Archean.
•87/86Sri from apatite trace multiple precursor composition of Archean granitoids.•Granitoids in the western part of Singbhum Craton preserve 87/86Sri in apatite.•Sri - εHfi modelling revels a billion years crustal growth in the Singhbhum Craton.•Paleoarchean continental crust was derived by re-melting of Eoarchean mafic crust.
Context: Regression testing is an important activity that allows ensuring the correct behavior of a system after changes. As the system grows, the time and resources to perform regression testing ...increase. Test Suite Reduction (TSR) approaches aim to speed up regression testing by removing obsolete or redundant test cases. These approaches can be classified as adequate or inadequate. Adequate TSR approaches reduce test suites and completely preserve test requirements (e.g., covered statements) of the original test suites. Inadequate TSR approaches do not preserve test requirements. The percentage of satisfied test requirements indicates the inadequacy level.
Objective: We compare some state-of-the-art adequate and inadequate TSR approaches with respect to the size of reduced test suites and their fault-detection capability. We aim to increase our body of knowledge on TSR approaches by comparing: (i) well-known traditional adequate TSR approaches; (ii) their inadequate variants; and (iii) several variants of a novel Clustering-Based (CB) approach for (adequate and inadequate) TSR.
Method: We conducted an experiment to compare adequate and inadequate TSR approaches. This comparison is founded on a public dataset containing information on real faults.
Results: The most important findings from our experiment can be summarized as follows: (i) there is not an inadequate TSR approach that outperforms the others;
(ii) some inadequate variants of the CB approach, and few traditional inadequate approaches, outperform the adequate ones in terms of reduction in test suite size with a negligible effect on fault-detection capability; and (iii) the CB approach is less sensitive than the other inadequate approaches, that is, variations in the inadequacy level have small effect on reduction in test suite size and on loss in fault-detection capability.
Conclusions: These findings imply that inadequate TSR approaches and especially the CB approach might be appealing because they lead to a greater reduction in test suite size (with respect to the adequate ones) at the expense of a small loss in fault-detection capability.
U–Pb and Hf isotope analysis of zircons from granitoids of the Permian–Triassic New England Batholith (eastern Australia) was carried out to provide constraints on the evolution of an isotopically ...and compositionally diverse batholith. Incipient plutonism in the early Permian resulted in the formation of isotopically evolved, peraluminous granodiorites of the Hillgrove Suite. Following this, mixing between crustal-derived (+5–+8 εHf units) and depleted mantle-derived magmas (+13–+18 εHf units), was responsible for the formation of the c. 282Ma Bundarra Suite. The strongly metaluminous and isotopically depleted granites of the c. 268Ma Clarence River Suite (+11–+16 εHf units) signify an increased role of isotopically depleted magmas during the formation of plutonic rocks in the middle Permian. Interestingly, this isotopic and chemical transience coincides with orogenic extension that was associated with the relocation for the southern New England Orogen (NEO) from a continental margin accretionary setting to that of a back-arc basin. Following attenuation, the NEO was thickened by contraction during the Hunter Bowen Event (265–255Ma).
Forming after the Hunter Bowen Event, the metaluminous rocks of the c. 256Ma Moonbi Suite were the product of mixing between magmas derived from evolved metaigneous rocks and enriched mantle (+3–+8 εHf units). We attribute the switch in isotopic character from highly depleted (i.e., Clarence River Suite) to evolved (i.e., Moonbi Suite) to crustal thickness before (i.e., thin) and after (i.e., thick) the Hunter Bowen Event. Evidence of renewed mixing between depleted and evolved magmas characterises the formation of the c. 249Ma Uralla Suite (+7–+16 εHf units), which interestingly, was coeval with renewed orogenic extension in the early Triassic. Finally, the melting of deep crustal basalts below the southern New England Orogen in the middle Triassic (c. 233Ma) resulted in the formation of moderately depleted leucomonzogranites and A-type magmas (+9–+12 εHf units).
Through combining new U–Pb and Hf zircon isotope data with pre-existing whole rock Nd and geochemical data, a link between geodynamic setting and granite petrogenesis has been identified, where: (i) in thick orogens, granites formed via partial melting of the crust and lack a significant depleted component; (ii) in thin orogens, granites form by mixing of crustal-derived and depleted mantle-derived magmas; and (iii) in highly attenuated orogens, granites can be extremely depleted and dominantly derived from the melting of upper mantle sources. This relationship may be associated with the development or reactivation of lithosphere scale detachments during orogenic extension that could facilitate the transportation of depleted magmas into the crust.
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▶ U-Pb and Hf isotope analysis of zircon reveal a link between granite petrogenesis and geodynamic setting. ▶ Hf isotopes show a significant contribution of depleted magmas in granites that formed in an attenuated orogen. ▶ Granites that form in thick orogens are largely composed of evolved magmas. ▶ The development of lithosphere scale detachments during orogenic extension could facilitate the transportation of depleted magmas into the crust.
•Two new igneous suites are defined, the Kayilirra Suite (ca. 1500 Ma) and the Kalyukuyarra Suite (ca. 1185–1165 Ma).•Zircon Lu-Hf isotope data and Sm-Nd whole rock data indicate a mixture of crustal ...reworking and crustal growth during the Mesoproterozoic.•Lu-Hf isotope arrays display positive “steps” and dilution of older isotope signatures with the addition of mantle-derived magmas to the crust.•The Rudall Province, Western Australia, shares a Mesoproterozoic evolution with the west Musgrave Province suggesting they were both part of the West Australian Craton.
The Rudall Province in Western Australia is a key crustal component in the amalgamation of the Rodinia supercontinent. New field observations, U–Pb zircon geochronology and geochemistry identify three previously unrecognised Mesoproterozoic magmatic events in the eastern Rudall Province. The Kayilirra Suite formed at ca. 1500 Ma and is a magnesian, calc-alkalic to alkali-calcic and weakly peraluminous suite with a limited SiO2 range of 69–70 wt%. The suite is interpreted to have formed in either a post-tectonic or rift-related setting. The Kalyukuyarra Suite formed at ca. 1185–1165 Ma and was synchronous with a peak in magmatic activity in the along-strike Musgrave Province. The suite is magnesian to ferroan, alkali-calcic and calc-alkalic, high K and peraluminous. Abundant inherited zircon grains indicate a dominantly crustal origin for the suite with only minor interpreted mantle input. Newly identified mafic and felsic magmatism was associated with the ca. 1380–1275 Ma Parnngurr Orogeny and further establishes correlations with the Mount West Orogeny in the Musgrave Province and “Stage 1” of the Albany-Fraser Orogeny. The new data support the progressive, final amalgamation of the Australian-Antarctic crustal fragments during the period ca. 1380–1250 Ma through consumption of oceanic crust below the over-riding West Australian Craton.
•A continuum of Paleoproterozoic heritage, seen in Nd model ages, from N to S in the Bushmanland Domain (BD), with the Buffels River shear zone simply a regional discontinuity.•The southern BD (SBD) ...has a greater juvenile component than the northern BD (NBD), becoming more dominant post-1.10 Ga.•Orthogneisses derived from crustal magmas with subduction-influenced signatures with mixed Meso- to Paleoproterozoic model ages. The SBD Koperberg Suite derived from low degrees of melting of enriched SCLM, but at deeper levels than those of the NBD.•The paragneisses derived from largely reworked, mixed Meso- to Paleoproterozoic felsic to intermediate sources.•Paragneisses derived from largely reworked, mixed Meso- to Paleoproterozoic felsic to intermediate sources.•SBD Koperberg Suite derived from low degrees of melting of enriched SCLM, but at somewhat deeper levels than NBD Koperberg magmas.•D2 deformation constrained to ~ 1.11-1.09 Ga, with peak M3 metamorphism at ~ 1.05-1.02 Ga.
The timing of tectonomagmatic events and petrogenesis of ortho- and paragneisses within the high-grade southern Bushmanland Domain (SBD) of the Namaqua Metamorphic Province is, largely, poorly constrained. U-Pb age dating and whole rock lithogeochemistry of the rocks of the upper granulite facies Kliprand dome provide constraints with regards to the evolution of the SBD during the 1.2–1.0 Ga Namaquan Orogeny.
The SBD has a greater juvenile component, particularly added between ∼1.1 and 1.02 Ga, compared to the northern Bushmanland Domain (NBD). This is reflected in marginally younger TDM model ages (1.60–1.95 Ga) than for the NBD (∼1.9–2.4 Ga), and higher εNd(t) values for magmatic rocks, particularly for the late- to post-tectonic Spektakel Suite (SS), concentrated in the SBD. The ∼1.06 Ga Klein Lieslap Charnockite of the SS was derived from reworking of radiogenic Paleoproterozoic arc crust, but has a large juvenile depleted component compared to that of the ∼1.19 Ga Grootberg Gneiss of the syn-tectonic Little Namaqualand Suite.
SBD mafic magmas were derived from low degrees of partial melting of subduction-influenced enriched subcontinental lithospheric mantle. The pre-tectonic ∼1.17 Ga Oorkraal Suite shows limited crustal contamination of mantle-derived melts. The post-tectonic ∼1.05 Ga Koperberg Suite was derived from deeper mantle melting than that in the NBD, but shows less crustal contamination. The supracrustal Kamiesberg Group was derived from mixed, reworked Meso- to Paleoproterozoic crust that showed a more dominant depleted component compared to that in the NBD. Incongruent anatexis of the paragneisses gave rise to crosscutting garnetiferous quartzofeldspathic segregations, notably the strongly peraluminous ∼1.07 Ga Ibequas Leucogranite.
D2 deformation, at ∼1.11–1.09 Ga, resulted in penetrative foliation. D3 deformation, related to the development of a sub-vertical foliation in the limbs of F2 folds, is constrained to ∼1.07–1.06 Ga, between emplacement of the Ibequas Leucogranite and the Koperberg Suite. Peak granulite facies M3 metamorphism occurred at ∼1.05–1.02 Ga. These age constraints are similar to those of the NBD reflecting a synchronous tectonomagmatic and kinematic history. The SBD represents a deeper crustal level with a greater mantle influence than the NBD.
Apatite inclusions hosted by zircon offer a means to probe the magmatic history of granitic rocks and better constrain the volatile budgets of crystallising granitic melts. Building on recently ...developed F–Cl–OH partitioning models for apatite and coexisting melt, we outline an approach for estimating the melt concentrations of F and Cl from the composition of apatite inclusions in zircon, constrained by Ti-in-zircon crystallisation temperatures. The melts in equilibrium with apatite inclusions in zircon for the ‘I-type’ Jindabyne, Why Worry and Cobargo granitic suites of the Lachlan Orogen (eastern Australia), have Cl concentrations of 20–2880 ppm and F concentrations of 65–575 ppm. Variations in melt Cl and F concentrations between the granitic suites is attributed to differences in source compositions, specifically the relative contribution of F-rich turbiditic sediments and Cl-rich juvenile arc magmas. Within individual granitic suites, the calculated melt F and Cl concentrations decrease with magmatic differentiation and falling melt temperatures, and this appears to reflect the partitioning of Cl and F into biotite and hornblende, and into exsolving aqueous fluids. This study demonstrates that apatite-melt exchange coefficients for F, Cl and OH can be applied to apatite inclusions in zircon to quantify the F and Cl content of the melt, without additional context from the host rock samples.
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•The primitive bimodal magmatism of the Longwood Suite occurred from 261 to 243 Ma.•Granitoid geochemistry requires shallow melting of an amphibolitic residue.•The Longwood Suite has ...a significantly lower areal addition rate than the later arc.•Thinned Gondwana crust was tectonically underplated by Permian arc lithosphere.
The Cambrian to Cretaceous Tuhua Intrusives, New Zealand, preserve an igneous record of Phanerozoic subduction and crustal growth at the margin of Gondwana. Within the Tuhua Intrusives, the coeval gabbroic and trondhjemitic intrusions of the c. 261–243 Ma Longwood Suite stand out as being isotopically more primitive and chemically distinct from all other New Zealand plutonic suites. We present new U-Pb crystallization ages, trace element analyses and Sr-Nd isotope compositions of the Longwood Suite. U-Pb SHRIMP zircon ages of 258.5 ± 2.5 Ma, 256.0 ± 1.8 Ma, 247.8 ± 2.7 Ma and 243.2 ± 2.4 Ma obtained from plutons on Ruapuke Island, and a dike at Bluff, affirm the restricted time range and expand the known areal extent of the Longwood Suite. Longwood Suite granitoids are I-type and sodic (K/Na < 0.4), with distinctive low Rb and Nb/Ta, flat rare earth element patterns (La/YbN < 10), unradiogenic 87Sr/86Sr(t) (0.7029 to 0.7032) and radiogenic ε143Nd(t) (+6.3 to +8.2), compared to the nearby, calc-alkaline, Late Triassic Darran Suite I-type plutons of the Tuhua Intrusives. Stable Nd isotope ratios of Longwood Suite samples are highly variable (δ146/144Nd = 233 ppm) compared to global plutonic rocks (δ146/144Nd = 44 ppm) and reflect the removal of phosphate minerals. Collectively, these geochemical characteristics are consistent with generation of the granitoids by shallow (garnet-absent) melting of an amphibolitic residue, from which we infer relatively thin lithosphere. The Longwood Suite has a maximum areal addition rate of 43 km2/Ma, substantially less than the subsequent plutonic suites when the magmatic arc was fully established. We suggest a petrotectonic model whereby Gondwana continental margin crust was tectonically underplated by Permian intra-oceanic island arc crust and mantle lithosphere, which subsequently melted to generate the isotopically primitive gabbro and trondhjemite plutons of the Longwood Suite.
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