Juvenile Material Research Articles

The U-Pb Zircon Geochronology (LA-ICP-MS) of Geological Processes in Granulites of Middle Bouh Area. Article 2. Rock association in the Chausove open pits

The LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charnockitoids that crop out in the open pits near Chausove village, Pervomaisk district. The association of enderbite gneisses, mafic and ultramafic (pyroxenite) granulites and vein bodies of pink biotite granites occur in the open pits. Enderbites are rather heterogeneous, and their composition varies from leucocratic quartzite-like rocks to enderbite-diorite. The Pervomaisk open pit is located within charnockite massif. Our data indicates that the association of enderbites and charnockites crystallised at 2850-2760 Ma from juvenile material (Hf isotope composition in zircons from enderbite-diorite is 176Hf/177Hf = 0.280915 ± 12, εHf2850 = +2; from leucocratic charnockite 176Hf/177Hf = 0.280875 ± 12, εHf2760 = –1; and from charnockite 176Hf/177Hf = 0.280875 ± 12, εHf2760 = –1). These rocks represented the newly formed Meso-Neoarchean crust, in contrast to the reworked older continental crust. This association has experienced a significant transformation in Paleoproterozoic. The last stage of transformation was accompanied by crystallisation of a new generation of zircon and formation of monazite at 2.04-2.06 Ga.

Vegetative rescue of Camu-Camu from epicormic sprouts of detached branches

Abstract The cloning of camu-camu by cuttings has shown distinct and sometimes controversial results. The use of juvenile materials has been indicated for difficult rooting species. Thus, this work aimed to evaluate the emission of epicormic sprouts in mega-cuttings and cuttings of detached branches, as well as the cloning of camu-camu from these sprouts. The research was developed by conducting four experiments, the first two being related to the emission of epicormic sprouts, while the others referred to the cloning of camu-camu from these sprouts. In experiments evaluating sprout emission, the following factors were studied: mother plant x branch position; mother plant x substrate. In the other tests, using standard cuttings with two pairs of leaves made from epicormic sprouts, the following factors were evaluated: mother plant x cutting type x indolbutyric acid concentration (IBA); mother plant x hydroretentive polymer x environment. The number and speed of sprouts vary depending on the mother plant. IBA has negative influence on cutting and cuttings from the lower portion of sprouts have greater rooting potential than those from the upper portion. Environment with intermittent mist irrigation is more suitable for the propagation of camu-camu by cuttings. Vegetative rescue by means of epicormic sprouts in mega-cuttings and cuttings of detached branches presents potential application for the clonal propagation of camu-camu, requiring improvement in order to increase efficiency.

Ancient crustal recycling in modern island arcs: A tale of the world's youngest charnockite from SW Japan

Modern accretionary orogens are considered as zones of extensive juvenile crustal growth on our planet with the Central Asian Orogenic Belt (CAOB) and the western Pacific domain as typical examples. Here we report magmatic charnockites (orthopyroxene-bearing anhydrous monzogranite) from the Shikoku Island in SW Japan intruding the Shimanto accretionary belt. Petrological and geochemical features of the intrusion are identical to Archean, Paleoproterozoic and Cretaceous charnockites from various parts of the world and show typical arc magmatic affinity and formation in a convergent margin setting. Zircon UPb data indicate that the pluton was emplaced at 13.75 Ma, revealing one of the youngest magmatic charnockite occurrences in the world. Zircon LuHf data yield epsilon Hf(t) values in the range of −3.2 to 2.8 suggesting that the magma source involved a substantial amount of reworked material, in addition to juvenile input. The Hf modal age (TDM) shows a major peak at 701 Ma, suggesting reworking of Neoproterozoic basement rocks beneath the young island arc. The data confirm the model of the birth of Proto-Japan along the periphery of the Cathaysia block in South China. The modal age peak corresponds to the timing of magmatism associated with Rodinia rifting. Our study provides evidence for the involvement of both ancient recycled components and juvenile material associated with crust building in a young island arc within an ongoing subduction system.

Long-lived localized magmatism in central-eastern part of the Pernambuco-Alagoas Domain, Borborema Province (NE Brazil): Implications for tectonic setting, heat sources, and lithospheric reworking

Magmatic activity circumscribed to a restricted area lasting for tenths of millions of years allows to link changes in magma chemistry to deformation, and thus to determine the tectonic evolution of a region. Here we describe an area of about 180 × 40 km in eastern Borborema Province (northeastern Brazil) where several pulses of magmatism occurred in the time interval 656–562 Ma. The oldest pulses are represented by orthogneisses bearing a flat-lying foliation resulting from deformation and metamorphism of granitoids emplaced in three stages: 656–645 Ma, 632–618 Ma, and 606–597 Ma. The oldest and most important unit (656–652 Ma-old) has large length/width ratio (c. 10), alkali-calcic signature, lacks pronounced negative Ta anomalies whereas showing positive Hf and Zr anomalies in normalized trace element diagrams, and yields crystallization age similar to the deposition age of surrounding, dominantly clastic metasedimentary units. These characteristics point to emplacement in an extensional setting and most probably fit in a rift/sag basin model, with thermal thinning of the lithosphere generating regional subsidence and magmatism. Rocks related to the 632–618 Ma-old stage are represented by orthogneisses with petrographic and geochemical characteristics akin to I-type granites, indicating a shift to an orogenic setting at around 640–630 Ma. Increased radioactive heating during continued thickening promoted anatexis of metasedimentary rocks at mid-crustal levels and segregation of small volumes of peraluminous melts at 606–597 Ma. The subsequent period of magmatic activity at 587–581 Ma witnesses the transition to a transcurrent regime, with intrusion of large granitic and syenitic batholiths with high-K calc-alkalic to shoshonitic affinity. Intrusion of these plutons added to heat resulting from strain heating to produce peraluminous granites at 573–566 Ma through partial melting of metasedimentary sources. The final magmatic episode at c. 562 Ma suggests involvement of the lithospheric mantle and crustal sources, perhaps related to localized delamination. Generally, younger orthogneisses and plutons contain zircons inherited from previous magmatic events, pointing to important crustal reworking. Together with the geochemistry of the rocks, these results imply only modest addition of juvenile material and thus no net crustal growth in eastern Borborema Province during the 660–560 Ma time interval.

Early Paleozoic Granite in the Talate Mining District, Chinese Altay, and its Geological Significance for the Altay Orogenic Belt

Zircon dating, geochemical and Nd‐Sr isotopic analyses have been determined for samples from two granitic intrusions in the Talate mining district, Chinese Altay. Our data suggest that these intrusions were emplaced from 462.5 Ma to 457.8 Ma. These rocks have strong affinity to peralumious S‐type granite and are characterized by prominent negative Eu anomalies (δEu=0.20–0.35), strong depletion in Ba, Sr, P, Ti, Nb, Ta and positive anomalies in Rb, Th, U, K, La, Nd, Zr, Hf. Nd‐Sr isotopic compositions of the whole rock show negative ∊Nd(t) values (−1.21 to −0.08) and Mesoproterozoic Nd model ages (T2DM=1.20–1.30 Ga). Their precursor magmas were likely derived from the partial dehydration melting of Mesoproterozoic mica‐rich pelitic sources and mixed with minor mantle‐derived components, under relatively low P (≤1 kbar) and high T (746–796°C) conditions. A ridge subduction model may account for the early Paleozoic geodynamic process with mantle‐derived magmas caused by Ordovician ridge subduction and the opening of a slab window underplated and/or intraplated in the middle–upper crust, which triggered extensive partial melting of the shallow crust to generate diverse igneous rocks, and provided the heat for the crustal melting and juvenile materials for crustal growth.

Age and geological context of the Barby Formation, a key volcanic unit in the Mesoproterozoic Sinclair Supergroup of southern Namibia

Abstract Volcanic and sedimentary rocks of the Sinclair Supergroup occur in the Konkiep Terrane of Southern Namibia. Three volcanic and sedimentary cycles are recognised. In this work we describe and date volcanic rocks of the Barby Formation, a key unit in the Sinclair area. The coeval Spes Bona Syenite and the Tiras Granite Gneiss are also described and dated. The rock types in the Barby Formation are rhyolites, basaltic trachyandesites, trachybasalts and trachydacites as well as volcanoclastic rocks. The rocks are largely undeformed and partly altered by deuteric and contact metamorphic processes but not regionally metamorphosed. Our samples represent both the calc-alkaline and alkaline trends documented in previous work. U-Pb ion probe and laser ablation inductively coupled plasma (LA-ICP) multicollector mass spectrometer Lu-Hf microbeam analyses were made of zircon and baddeleyite grains from four samples. A felsic tuff sample from the base of the Barby Formation has a 207Pb/206Pb zircon age of 1214 ± 5 Ma (2σ). A rhomb porphyry sample from the top of an 8.5 km-thick stratigraphic section gives a 207Pb/206Pb baddeleyite age of 1217 ± 2 Ma. The Spes Bona Syenite which intrudes the top of the Barby Formation has a 207Pb/206Pb baddeleyite age of 1217 ± 3 Ma and an indistinguishable LA-ICP collision cell mass spectrometer Rb-Sr biotite isochron age of 1238 ± 20 Ma, showing that there was no >350°C regional metamorphic event. Multi-element diagrams for the calc-alkaline samples show a dominant signature of reworked crust which is superimposed on a possible subduction signature. However the alkaline samples contain clear subduction signatures which are not seen in the underlying 1.37 Ga Kumbis rhyolite. The Barby Formation samples and coeval Spes Bona Syenite have Lu-Hf crustal residence ages between 1682 and 1873 Ma, suggesting that both of these units formed from a mixture of juvenile mantle-derived and older crustal material. The Barby Formation is considered to have originated due to a subduction event which took place during the assembly of the Rodinia supercontinent. The duration of the Barby magmatic episode is constrained to a maximum 9 m.y. period between 1219 and 1210 Ma, and during this period the Konkiep Terrane was an active continental margin. The 1204 ± 9 Ma Tiras Granite Gneiss is slightly younger than the Barby Formation and intruded across the Lord Hills Shear Zone, which is the suture between the hardly metamorphosed Konkiep Terrane and the highly metamorphosed Grunau Terrane of the Namaqua-Natal Province. Its intrusion reflects the end of subduction-related volcanism, due to the collision of Namaqua terranes with the Konkiep Terrane.

Devonian to carboniferous tectonic evolution of the Kangguer Ocean in the Eastern Tianshan, NW China: Insights from three episodes of granitoids

Deciphering the tectonic evolution of the Kangguer Ocean is critical to understand the architecture of the Eastern Tianshan, NW China. Previous studies for the Kangguer Ocean mainly concentrated on final closure during the Latest Carboniferous to Permian. Three distinct episodes of granitoids have been recognized in the Kangguer belt: Late Devonian (ca. 360 Ma) normal I-type granites, Early Carboniferous (ca. 348 Ma) fractionated I-type granites, and Late Carboniferous (ca. 317–302 Ma) adakitic granites, attempting to provide constraints on the sources of these rocks, which further unravels the evolution of the Kangguer Ocean during this period. The Late Devonian granites exhibit calc-alkaline characteristics, with negligible Eu anomalies and low (K2O + Na2O)/CaO ratios, akin to I-type granites without significant fractional crystallization. They display high SiO2 (>70 wt.%), with low MgO (<0.83 wt.%) and Mg# (35–41) values, together with depleted Sr and Nd isotopic values ((87Sr/86Sr)i = 0.7041; εNd(t) = 5.48–6.38) and juvenile TDM2 values (596–671 Ma), suggesting that they were probably originated from the lower crustal-derived juvenile materials. The Early Carboniferous granites have similarly depleted Sr and Nd isotopic values to those of the Late Devonian samples, but display striking depletions in Eu and Sr and have lower Mg# (26–29) values and higher (K2O + Na2O)/CaO ratios, indicating that they also represent juvenile crustal-derived magmas, but experienced extensive crystal fractionation. The Late Carboniferous rocks exhibit high SiO2 (63.7–69.0 wt.%), Sr/Y (17.4–83.3), La/Yb (4.00–13.7), and Na2O/K2O (1.66–7.03) values, and low Y (4.46–12.2 ppm) and Yb (0.50–1.10 ppm) contents, indicative of adakitic affinity. The above geochemical features, together with Sr and Nd isotopic values comparable to slab-derived adakites and ophiolitic rocks in the Kangguer belt, implying they were likely formed by slab-derived magmas and mantle wedge peridotites. Coupled with regional geology, a northward subduction of the Kangguer oceanic slab was suggested to interpret the formation of the Late Devonian normal I-type granites. Subsequently, the southward rollback of the Kangguer Ocean caused the generation of the Early Carboniferous granites with further fractional crystallization. We infer that a northward flat subduction resulted in formation the Late Carboniferous adakitic rocks.

The Neoproterozoic basement of the Sauce Chico Inlier (Ventania System): Geochemistry and U–Pb geochronology of igneous rocks with African lineage in central-eastern Argentina

This study describes the geology, geochemistry, and LA-ICP-MS U–Pb geochronology of igneous rocks that crop out in the Sauce Chico Inlier (SCI) and constitute the Neoproterozoic basement of the Ventania System, Argentina. Magmatism registered in the SCI has developed in two phases. The first phase, of Tonian age, is represented by rift-related calc-alkaline and alkaline granites with ages of 783.8 ± 3.7 Ma (εNd(t) = −7.20) and 776.5 ± 4.7 Ma (εNd(t) = +1.65), respectively. This phase would be related to the break-up of the Rodinia supercontinent and subsequent opening of the Adamastor Ocean. In the Dom Feliciano Belt of southern Brazil and eastern Uruguay, the Tonian magmatism is represented in the Cerro Olivo Complex of the Punta del Este Terrane and in basement inliers of the Pelotas Batholith. The second phase, of Ediacaran age, started with the intrusion of syn-orogenic calc-alkaline granites (620.8 ± 5.8 Ma and 620.3 ± 2.5 Ma; εNd(t) = −9.94/−9.18) and continued with the extrusion of post-orogenic alkaline (577.3 ± 3.9 Ma; εNd(t) = −6.29) and calc-alkaline (543.6 ± 4.0 Ma; εNd(t) = −3.38) acid volcanic rocks. This phase would be related to the closure of the Adamastor Ocean, generation of a magmatic arc along the western margin of the Kalahari Craton, and collision between this and the Río de la Plata Craton. A post-collisional magmatism would have developed due to orogenic collapse (< 580 Ma). With the exception of the Tonian alkaline granite, in the remaining SCI igneous rocks, the juvenile component becomes more important as the crystallization age decreases. The available Nd model ages are between 1.80 and 1.14 Ga and suggest a mixing of older crust with juvenile material. The tectonic evolution of the Ventania System basement is consistent with that observed in the Dom Feliciano Belt and its African counterparts. We present here the first evidence of Tonian magmatism in the Ventania System basement. The results presented here also confirm those obtained previously by other authors. Zircon cores from the SCI igneous rocks have U–Pb inherited ages between ca. 1200 and 900 Ma that could be indicative of a lineage with the Gariep Belt and its Namaqua basement in southwestern Africa.

Zircon U–Pb and Lu–Hf systematics of the major terranes of the Western Superior Craton, Canada: Mantle-crust interaction and mechanism(s) of craton formation

Paleo-to Neoarchean granitoid gneisses (ca. 3.30 to 2.49 Ga) are well preserved in the Western Superior Craton. Protoliths of these gneisses are mainly I-type granitoids characterized by high Sr/Y and La/Yb ratios and low Mg#, consistent with Archean tonalite-trondhjemite-granodiorites. Zircons from granitoid gneisses commonly contain three growth phases: inherited cores (zircon I), magmatic rims (zircon II) and outer rims that have undergone Pb-loss (zircon III). The 3.12 Ga to 2.86 Ga zircon I represent early crustal material, that was captured in younger zircons; zircon II preserve crustal re-working and younger crustal additions that are constrained between 2.85 to 2.72 and 2.69 to 2.65 Ga.Zircon II contains both positive and negative εHf(t) values (−6.3 to +8.1), with both depleted-mantle and older crustal signatures. Half of the magmatic rims (II) are characterized by depleted mantle signatures with positive εHf(t) values representing juvenile crust-forming events, whereas the other half are characterized by recycled crustal signatures with negative εHf(t) values. εHf(t) results show that the North Caribou and the Island Lake terranes and the northern Uchi domain are isotopically more enriched than the southern Uchi, English River, Wabigoon and Winnipeg River terranes, suggesting the northern Uchi margin represents a major terrane boundary.Based on mass balance calculations, large volumes of juvenile material at circa 3.0 Ga mixed with smaller amounts of older crust. The vast majority of the granites were derived from a source with about 50% mantle material during the peak crust formation events after 2.8 Ga. The decline in the volume of felsic magmatism in the later Archean is coeval with a reduced supply of both heat and material from depleted mantle sources. Combined with previously published geochemical, geochronological and isotopic data, this suggests an evolution in felsic magma sources consistent with crustal thickening.

Carboniferous Highly Fractionated I‐type Granites from the Kalamaili Fault Zone, Eastern Xinjiang, NW China: Petrogenesis and Tectonic Implications

Carboniferous magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt (CAOB). However, the final closure time of the Kalamaili Ocean between East Junggar and Harlik Mountain is still debated. Early Carboniferous (332 Ma) and late Carboniferous (307–298 Ma) granitic magmatism from Kalamaili fault zone have been recognized by LA‐ICP‐MS zircon U‐Pb dating. They are both metaluminous highly fractionated I‐type and belong to the high‐K calc‐alkaline. The granitoids for early Carboniferous have zircon εHf(t) values of –5.1 to +8.5 with Hf model ages (TDM2) of 1.78–0.83Ga, suggesting a mixed magma source of juvenile material with old continental crust. Furthermore, those for late Carboniferous have much younger heterogeneous zircon εHf(t) values (+5.1 to +13.6) with Hf model ages (TDM2=1.03–0.45 Ga) that are also indicative of juvenile components with a small involvement of old continental crust. Based on whole‐rock geochemical and zircon isotopic features, these high‐K granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor AFC (assimilation and fractional crystallization). The juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling. These Carboniferous highly fractionated granites in the Kalamaili fault zone were probably emplaced in a post‐collisional extensional setting and suggested vertical continental crustal growth in the southern CAOB, which is the same or like most granitoids in CAOB. This study provides new evidence for determining the post‐accretionary evolution of the southern CAOB. In combination with data from other granitoids in these two terranes, the Early Carboniferous Heiguniangshan pluton represents the initial record of post‐collisional environment, suggesting that the final collision between the East Junggar and Harlik Mountain might have occurred before 332 Ma.

Complex magma sources of late Mesozoic granites along the southern margin of the North China Craton: constraints from geochemistry and geochronology of the massive Heyu and Lantian plutons

ABSTRACT Mesozoic granitoid rocks in the eastern Qinling terrane along the southern margin of the North China Craton are significant for understanding geodynamics processes related to lithospheric delamination in the Late Mesozoic. In addition, these rocks have close genetic association with the largest Mo-(Au-Ag) polymetallic mineralization belt in China. In the present study, zircon U-Pb ages and elemental and Sr-Nd-Pb isotopic geochemistry are reported for two representative granite plutons (Heyu and Lantian) exposed in the eastern Qinling terrane. Granitoid rocks from both plutons are metaluminous to weakly peraluminous and are classified as I-type granite with formation ages of 145 ~ 135 Ma and 150 Ma, respectively. These rocks are characterized by adakite-like affinity without significant Eu anomalies. Both plutons have relatively high initial 87Sr/86Sr ratios ranging between 0.7063 and 0.7109 and variable εNd(t) values of – 29.2 to – 6.5. Their Pb isotopic compositions are comparable to those of old high-grade metamorphic basement rocks from the North China Craton but are different from those of country rocks from the Xiong’er and Taihua groups. These features indicate genesis via reworking of the lower crust beneath North China and partial involvement of juvenile crustal material to different extents. Occurrences of ca. 1000-Ma-old inherited zircon in the Lantian granites imply the contribution of the Qinling Group in North Qinling to the magma source(s). This magmatism occurred intensively in a transitional setting from compression to extension and was likely induced by lithosphere thinning and asthenosphere upwelling beneath eastern China during the Cretaceous.

The highly siderophile elements and Re–Os isotope geochemistry of Variscan lamproites from the Bohemian Massif: implications for regionally dependent metasomatism of orogenic mantle

Orogenic lamproites represent a group of peralkaline, ultrapotassic and perpotassic mantle-derived igneous rocks that hold the potential to sample components with extreme compositions from highly heterogeneous orogenic mantle. In our pilot study, we present highly siderophile element (HSE) and Re–Os isotope systematics of Variscan orogenic lamproites sampled in the territories of the Czech Republic, Austria and Poland, i.e., from the termination of the Moldanubian and Saxo-Thuringian zones of the Bohemian Massif. Orogenic lamproites of the Bohemian Massif are distinguished by variably high contents of SiO2, high Mg# and predominant mineral associations of K-rich amphibole and Fe-rich microcline. The HSE show (i) consistently very low contents in all investigated orogenic lamproites compared to the estimated concentrations in majority of mid-ocean ridge basalts, hotspot-related volcanic rocks (e.g., ocean island basalts, continental flood basalts, komatiites, some intraplate alkaline volcanic rocks such as kimberlites and anorogenic lamproites) and arc lavas, and (ii) marked differences in relative and absolute HSE abundances between the samples from the Moldanubian and Saxo-Thuringian Zone. Such a regional dependence in HSE from mantle-derived melts is exceptional. Orogenic lamproites have highly variable and high initial suprachondritic 187Os/188Os values (up to 0.631) compared with rather chondritic to subchondritic Os isotope values of the young lithospheric mantle below the Bohemian Massif. The highly radiogenic Os isotope component in orogenic lamproites may be derived from preferential melting of metasomatised vein assemblages sitting in depleted peridotite mantle. This process appears to be valid generally in the petrogenesis of orogenic lamproites both from the Bohemian Massif and from the Mediterranean area. As a specific feature of the orogenic lamproites from the Bohemian Massif, originally ultra-depleted mantle component correlative with remnants of the Rheic Ocean lithosphere in the Moldanubian Zone was metasomatised by a mixture of evolved and juvenile material, whereas the lithospheric mantle in the Saxo-Thuringian Zone was enriched through the subduction of evolved crustal material with highly radiogenic Sr isotope signature. As a result, this led to observed unique regionally dependent coupled HSE, Rb–Sr and Re–Os isotope systematics.

The crust-mantle evolution of the Anabar tectonic province in the Siberian Craton: Coupled or decoupled?

To clarify the tectonic-thermal evolution of the Anabar tectonic province in the central Siberian Craton, we performed an isotope-geochemical study of 20 xenoliths from the Udachnaya, Zarnitsa, and Komsomolskaya kimberlite pipes to represent different crustal levels. Most mafic granulites have Proterozoic Nd model ages and geochemical characteristics close to those of intraplate basalts, whereas some mafic and intermediate granulites with Archean model ages exhibit geochemical features of supra-subduction ophiolitic basalts. Analysis of U-Pb ages and hafnium isotopic composition of zircon indicates that the main tectonic-thermal events modified the crust at 2.7 and 1.9–1.8 Ga, which is consistent with ages of mantle depletion events from previous studies. All zircons have Archean Hf model ages (TDMC3.6-3.2 Ga). Overall, thermal events with ages of 2.9–2.8, 2.7, 2.4, 1.97 and 1.8 Ga have remarkable influence on the studied zircons. Tectono-thermal events at 2.4 1.97, 1.9 and 1.8 Ga with no addition of juvenile material are recorded by zircons from xenoliths of mafic and intermediate granulites and metadiorites. A compilation of isotope-geochemical data demonstrates that instead of age-stratified, the crust of the Anabar tectonic province consists of variably reworked Paleoarchean rocks and juvenile Proterozoic rocks at all crustal levels. Hence the crust and mantle of the Siberian Craton has been coupled since the Paleoarchean.

Nd isotopic stratigraphy of Paleoproterozoic to late Paleozoic sedimentary strata of the southwestern Yangtze Block and implications for its tectonic evolution

ABSTRACT A systematic Sm-Nd isotopic study is reported for Paleoproterozoic to Late Paleozoic strata from the Dongchuan area in the southwestern Yangtze Block. The results, combined with the available detrital zircon U-Pb ages and Hf isotope data, constrain the provenances of these sedimentary rocks and further identify three important tectono-magmatic activities. Most of the Paleo-Mesoproterozoic samples (Dongchuan Group) display a wide T DM2 range of 1.92–2.52 Ga with corresponding ε Nd(t) values of +4.0 to −3.5, suggesting Paleoproterozoic-dominated provenances mixed with mantle-derived materials. This corresponds to the ~1.7–1.5 Ga mafic magmatic activities commonly occurred in the southwestern Yangtze Block, which are related to the early breakup of the Columbia supercontinent. The obvious vale of T DM2 and apex of ε Nd(t) occurred in the Neoproterozoic strata (~0.8 Ga) of the southwestern margin over the whole Yangtze Block. This is consistent with the widely recognized mantle-derived magmatism around the Yangtze Block related to the breakup of Rodinia. However, the decreases in Nd model ages are different among various regions, indicating that the Neoproterozoic mantle inputs are more profound in the southwestern and central Yangtze Block than the southeastern Yangtze and the Jiangnan orogenic belt. The late Ediacaran to early Cambrian strata from the southwestern Yangtze exhibit a decrease in T DM2 (from 2.00 to 1.67 Ga) and increase in ε Nd(t) (from −9.0 to −5.2). This is in accordance with the coeval juvenile crustal materials discovered in the northwestern Yangtze, which were probably derived from the assembly of the Gondwana continent. Thus, a Gondwanan affinity is suggested for the southwestern Yangtze Block. Overall, the Nd isotopic studies of the Paleoproterozoic to Late Paleozoic sedimentary strata from the southwestern Yangtze Block identified three major episodes of magmatic activities, late Paleoproterozoic (~1.7 Ga), Neoproterozoic (~0.8 Ga) and late Neoproterozoic-early Cambrian (~0.55 Ga) in the context of Columbia, Rodinia and the subsequent Gondwana supercontinents.

The Early Jurassic Fe–Sn metallogenic event and its geodynamic setting in South China: Evidence from Re–Os, U–Pb geochronology and geochemistry of the Dading magnesian skarn Fe–Sn deposit

The South China Block (SCB) is one of the largest W-Sn-polymetallic metallogenic district over the world, with most of the deposits formed during the Mesozoic. The Early Jurassic of SCB was considered as a magmatic and metallogenic quiescence stage, as response to the tectonic transition from the paleo-Tethyan to the paleo-Pacific geodynamic domains. The Dading Fe-Sn deposit is a quite rare Early Jurassic deposit recognized in SCB. SIMS Zircon U–Pb and molybdenite Re-Os dating indicate that the Dading Fe–Sn deposit (185.9 ± 4.9 Ma) and related Shibei granite (189.0 ± 1.5 Ma) formed at the Early Jurassic, which provides convincing evidence for a previously unrecognized Early Jurassic Fe–Sn metallogenic event in SCB. Geochemical data show that the Shibei granite has high SiO2, Nb, Zr + Nb + Ce + Y concentrations and high Ga/Al ratio, but low Y/Nb ratio, which are similar to those of A1-type granite. The large range of zircon εHf(t) values (−2.4 to +3.4), negative correlation between zircon εHf(t) and δ18O values, and unique whole-rock Sr–Nd isotopic compositions (εNd(t) = −3.3 to −3.7; ISr = 0.7063 – 0.7085) suggest that the Shibei granite is likely to originate from a mixed source of pre-existing crust and juvenile material with OIB-like isotopic composition. Combining with the spatial distribution of the volcanic–intrusive rocks, sedimentary basins, and tectonic deformation styles, we suggest that the Early Jurassic Fe–Sn mineralization occurred in an extensional environment, which was probably linked to the post-orogenic collapse of the Indosinian orogeny between the SCB and Indochina Block.

Sedimentary provenance and age of the Langshan Group in the northeastern Alxa Block: implications for Neoproterozoic tectonic evolution

The origin and the Precambrian tectonic evolution of the Alxa Block have not been well studied, largely due to widespread desert coverage and a lack of high-resolution geochronological data. This paper reports zircon U–Pb ages and Hf isotopic data for the Langshan Group in the northeastern Alxa Block. Detrital zircons from the Langshan Group mainly provide U–Pb ages between ca. 2000 Ma and 1100 Ma, suggesting that their provenance was dominated by late Palaeoproterozoic to Mesoproterozoic rocks, which yield two main peak ages at 1592 Ma and 1745 Ma. These zircons possess eHf (t) values between − 15 and + 8, implying the derivation of their precursor magmas from old crust and juvenile materials. Zircon U–Pb dating yields ages of 898 ± 4 Ma and 808 ± 4 Ma for the granite cobbles in coarse conglomerate in the Fourth Formation and the diorite intruding into the Second Formation of the Langshan Group, which constrains the depositional age of the main part of the Langshan Group to between 898 and 804 Ma. Our data show that the Langshan Group was probably deposited in an intra-continental rift basin and originated from recycled orogens. The geochronology and palaeocurrent data indicate that the North China Craton (NCC) could not have provided source materials for the Langshan Group. Instead, the Langshan Group shares a similar origin and detrital zircon age spectrum with the Beishan Complex in the South Beishan Collage. Combining these findings with published data, we propose that the Alxa Block was not a part of the NCC during the Neoproterozoic but a Precambrian micro-continent block. The Alxa Block recorded footprints that are related to the late amalgamation of the Rodinia supercontinent and the initial breakup. We suggest that the Alxa Block laid between Australia and Laurentia in the Rodinia supercontinent during the Neoproterozoic.

Hf isotopic fingerprinting of geodynamic settings: Integrating isotopes and numerical models

Hf isotopes have proven invaluable in understanding the evolution of Earth's crust-mantle system, but their use in reconstructing tectonic environments, in many cases, remains equivocal. In this study, we introduce a new approach to predict the Hf isotopic evolutionary pattern for rifting and collision based on the integration of numerical models and 176Hf/177Hf isotopes. The geodynamic numerical models allow us to estimate the proportion of juvenile material added to the crust through time. On the basis of this proportion, we calculate changing 176Hf/177Hf ratios using mixing models. Predicted Hf isotopic patterns generated through this numerical approach imply that juvenile signals are observed during back-arc extension, whereas evolved signatures dominate collisional settings. We use this novel modeling approach in the case study region of the Halls Creek Orogen to elucidate its tectonic setting through time. In addition, the geochemical features of magmatic rocks in the case study region imply partial melting of a sub-arc mantle wedge with magma-crust interaction on ascent in a convergent margin setting. The links between predicted Hf isotopic evolution, geodynamic numerical models, whole rock geochemistry and measured zircon Hf isotopic evolution trend resolve three discrete stages in the tectonomagmatic development of the Halls Creek Orogen: (1) oceanic crust subduction; (2) back-arc formation with addition of juvenile mantle input; and (3) docking of the North Australian and Kimberley cratons resulting in the development of mixed-source magmatism formed in a collisional setting. We provide a new method to validate geodynamic models with isotopic datasets, which should lead to more rigorous understanding of crustal evolution.

Melt inclusion evidence for long term steady-state volcanism at Las Sierras-Masaya volcano, Nicaragua

Las Sierras-Masaya volcanic system is a persistently active basaltic caldera complex in Nicaragua. While there has been almost no juvenile material erupted since 1772, Masaya volcano has been persistently degassing for >150 years. An additional unusual behaviour for the Las Sierras-Masaya volcanic complex is its ability to produce large caldera-forming basaltic Plinian eruptions with the most recent occurring about 1800 years ago.Here we present melt inclusion analyses that provide constraints on the magmatic system over time. Melt inclusions hosted in plagioclase and olivine crystals were analyzed for major, trace and volatile elements (S, Cl, F, H2O). The data supports a consistent parental magmatic source with restricted compositional variability explained by simple fractional crystallization of plagioclase, olivine, clinopyroxene and magnetite at a nearly constant temperature. This broadly agrees with previous whole rock geochemical studies showing that the overall chemical signature of volcanic products at Masaya has remained largely unchanged for ~60,000 years and that both shallow fractionation and degassing processes dominate the whole evolution of the magmatic series. Based on volatile element in melt inclusions and gas composition and flux measurements, we determine the magmatic flux to be ~0.19 km3 yr−1 implying that up to 47 km3 of magma may have degassed since the last effusive eruption. As at other persistently active basaltic volcanoes (e.g., Mt. Etna, Italy; Kilauea, Hawaii, USA), this magmatic flux must involve significant endogenous storage which is likely accommodated by extensional tectonics. However, Masaya volcano differs in its apparent simplicity with respect to its stable chemistry and its fully interconnected magmatic system.

Cytological, Biochemical and Molecular Events of the Embryogenic State in Douglas-fir (Pseudotsuga menziesii [Mirb.]).

Somatic embryogenesis techniques have been developed for most coniferous species, but only using very juvenile material. To extend the techniques’ scope, better integrated understanding of the key biological, physiological and molecular characteristics of embryogenic state is required. Therefore, embryonal masses (EMs) and non-embryogenic calli (NECs) have been compared during proliferation at multiple levels. EMs and NECs originating from a single somatic embryo (isogenic lines) of each of three unrelated genotypes were used in the analyses, which included comparison of the lines’ anatomy by transmission light microscopy, transcriptomes by RNAseq Illumina sequencing, proteomes by free-gel analysis, contents of endogenous phytohormones (indole-3-acetic acid, cytokinins and ABA) by LC-MS analysis, and soluble sugar contents by HPLC. EMs were characterized by upregulation (relative to levels in NECs) of transcripts, proteins, transcription factors and active cytokinins associated with cell differentiation accompanied by histological, carbohydrate content and genetic markers of cell division. In contrast, NECs were characterized by upregulation (relative to levels in EMs) of transcripts, proteins and products associated with responses to stimuli (ABA, degradation forms of cytokinins, phenols), oxidative stress (reactive oxygen species) and carbohydrate storage (starch). Sub-Network Enrichment Analyses that highlighted functions and interactions of transcripts and proteins that significantly differed between EMs and NECs corroborated these findings. The study shows the utility of a novel approach involving integrated multi-scale transcriptomic, proteomic, biochemical, histological and anatomical analyses to obtain insights into molecular events associated with embryogenesis and more specifically to the embryogenic state of cell in Douglas-fir.

Geochronology, mineralogy, and geochemistry of the Late Triassic Xiuwacu biotite granite in the southern Yidun Terrane, southwest China: Insights into the petrogenesis and magmatic fertility

The southern Yidun Terrane formed in response to the westward subduction of the Garzê–Litang oceanic lithosphere. The Xiuwacu pluton, consisting of the Late Triassic biotite granite and Late Cretaceous monzogranite porphyry, is located in the northern portion of the southern Yidun Terrane. It hosts the Late Cretaceous quartz‐vein‐type Mo–W deposit genetically related to the intraplate monzogranite porphyry. However, the petrogenesis and magmatic fertility of the biotite granite remain unclear. Sixteen zircons from the biotite granite yield a weighted mean 206Pb/238U age of 217 ± 1.2 Ma, indicating that the biotite granite emplaced synchronously with the arc‐related andesites and porphyries in the southern Yidun Terrane. Unlike these slab melt‐derived adakitic rocks, the Xiuwacu biotite granites show typical I‐type granite affinities, with relatively high SiO2 contents, low Sr/Y ratios, and high Y contents. These granites display depleted zircon Hf isotopic signatures (ƐHf(t) = 0.6–3.8) but enriched whole‐rock Sr–Nd and zircon O isotopic signatures, suggesting that the mixing between juvenile materials and external enriched melts might have contributed to the generation of biotite granite. Moreover, they show relatively high Al2O3/(FeOT + MgO + TiO2), Th/Yb, and Th/Nb ratios, which are collectively indicative of the input of sediment melts extracted from subducting slab into the melt source of biotite granite. The high MgO, TiO2, F, and Cl contents of biotite and the excess Al of plagioclase suggest that the Xiuwacu biotite granites formed under high oxygen fugacities, magmatic water contents, and volatiles components and they might have Cu prospecting potentials.