It has been widely accepted that an active continental margin existed along the coast of Southeast China during the Mesozoic time that produced extensive magmatism in the region. However, there is ...little constraint as to when this active margin was first initiated. Here we present new SHRIMP U‐Pb zircon ages and geochemical and Sr‐Nd isotopic data for syntectonic granites on Hainan Island. Our data demonstrate that these rocks, dated at 267–262 Ma, are typical of calc‐alkaline I‐type granites formed in continental arc environments. The age of this magmatic arc coincides with a sudden change in sedimentary environments in South China during the Permian time, suggesting that the South China Indosinian Orogeny was likely contemporaneous with the onset of continental arc magmatism.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The South China Block, consisting of the Yangtze and the Cathaysia blocks, is one of the largest Precambrian blocks in eastern Asia. However, the early history of the Cathaysia Block is poorly ...understood due largely to intensive and extensive reworking by Phanerozoic polyphase orogenesis and magmatism which strongly overprinted and obscured much of the Precambrian geological record. In this paper, we use the detrital zircon U–Pb age and Hf isotope datasets as an alternative approach to delineate the early history of the Cathaysia Block. Compilation of published 4041 Precambrian detrital zircon ages from a number of (meta)sedimentary samples and river sands exhibits a broad age spectrum, with three major peaks at ~2485Ma, ~1853Ma and ~970Ma (counting for ~10%, ~16% and ~24% of all analyses, respectively), and four subordinate peaks at ~1426Ma, ~1074Ma, ~780Ma and ~588Ma. Five of seven detrital zircon age peaks are broadly coincident with the crystallisation ages of ~1.89–1.83Ga, ~1.43Ga, ~1.0–0.98Ga and ~0.82–0.72Ga for known igneous rocks exposed in Cathaysia, whereas, igneous rocks with ages of ~2.49Ga and ~0.59Ga have not yet been found. The Hf isotopic data from 1085 detrital zircons yield Hf model ages (TDMC) between ~4.19Ga and ~0.81Ga, and the calculated εHf(t) values between −40.2 and 14.4. The Archean detrital zircons are exclusively oval in shape with complicated internal textures, indicating that they were sourced by long distance transportations and strong abrasion from an exotic Archean continent. In contrast, the majority of detrital zircons in age between ~1.9 and ~0.8Ga are euhedral to subhedral crystals, indicative of local derivation by short distance transportations from their sources. The oldest crustal basement rocks in Cathaysia were most likely formed by generation of juvenile crust and reworking of recycled Archean components in Late Paleoproterozoic at ~1.9–1.8Ga, rather than in the Archean as previously speculated. Reworking and recycling of the continental crust are likely the dominant processes for the crustal evolution of Cathaysia during the Mesoproterozoic to Neoproterozoic time, with an intervenient period of significant generation of juvenile crust at ~1.0Ga.
Precambrian crustal evolutions of the Cathaysia Block are genetically related to the supercontinent cycles. By comparing detrital zircon data from Cathaysia with those for other continents, and integrating multiple lines of geological evidence, we interpret the Cathaysia Block as an orogenic belt located between East Antarctica, Laurentia and Australia during the assembly of supercontinent Columbia/Nuna at ~1.9–1.8Ga. The Cathaysia Block amalgamated with the Yangtze Block to form the united South China Block during the Sibao Orogeny at ~1.0–0.89Ga. The Laurentia–Cathaysia–Yangtze–Australia–East Antarctica connection gives the best solution to the paleo-position of Cathaysia in supercontinent Rodinia. The significant amount of ~0.6–0.55Ga detrital zircons in Cathaysia and West Yangtze have exclusively high crustal incubation time of >300Ma, indicating crystallisation from magmas generated dominantly by crustal reworking. This detrital zircon population compares well with the similar-aged zircon populations from a number of Gondwana-derived terranes including Tethyan Himalaya, High Himalaya, Qiangtang and Indochina. The united South China–Indochina continent was likely once an integral part of Gondwanaland, connected to northern India by a “Pan-African” collisional orogen.
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•Cathaysia Block formed at ~1.9-1.8Ga, rather than in Archean.•Archean detrital zircons found in Cathaysia were likely sourced from East Antarctica.•Cathaysia locates between E. Antarctica, Laurentia and Australia in Columbia/Nuna.•South China most likely locates in the interior, but not on fringe, of Rodinia.•South China connects with Northern India by a “Pan-African” collisional orogeny.
In tropics, especially Southeast Asia (SEA), heat wave (HW) research is seriously scarce although several global studies have projected this region to be greatly susceptible to increasing HW events ...under climate change scenarios. Using the recently released ERA5 reanalysis data, we find that in most parts of SEA, HWs are becoming more frequent, longer-lasting and stronger, no matter using dry-bulb or wet-bulb temperatures to define HW. The increasing trends of HW characteristics based on minimum temperatures are larger than those based on maximum temperatures, suggesting an alarming situation of anomalously warm night. HW characteristics based on wet-bulb temperatures show higher increasing rates in the IndoChina Peninsula and Malay Peninsula than those based on dry-bulb temperatures. Nearly all HW characteristics are significantly correlated with El Niño index, but Indian Ocean Dipole only significantly impacts HW characteristics based on wet-bulb temperature in Java. Results derived from other reanalysis products exhibit general agreement with those from ERA5, lending support to the findings reported herein. This study highlights the different role of humidity in changing HW trends in different regions of SEA, and calls for attention to the associated risk of increasing nighttime temperatures during HWs.
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•Heat waves are becoming more frequent, longer-lasting and more intense in most Southeast Asia.•HWs based on minimum temperatures increase at higher rate than based on maximum temperatures.•Wet-bulb temperature based HWs show larger increasing trends in Malay and Indochina Peninsulas.•Nearly all HW metrics are significantly correlated with El Nino index, but IOD only impacts Java.•Comparison with different reanalysis datasets demonstrates robustness of our findings.
Detrital zircon provenance data for the Tananao schist in eastern Taiwan is consistent with its protolith being deposited on the South China continental margin at around, or soon after, 150Ma, rather ...than being of an exotic origin and much older as previously suggested. The absence of ca. 200Ma zircons agrees with the presence of a magmatic gap in the region after the orogenic and magmatic front migrated to central South China, due to a flat-slab subduction. The characteristic lack of input from interior South China (i.e., the lack of 1100–750Ma and 470–420Ma populations), and the immature nature of some of the schist units, suggest that they were sourced from the nearby coastal regions. On the other hand, they exhibit a dominant 190–150Ma magmatic zircon population, suggesting the presence of abundant magmatic rocks of that age along the coastal regions. This, along with our newly discovered ca. 180Ma I-type granites from eastern Zhejiang and other ca. 190–180Ma magmatic rocks recently reported from the coastal regions, led us to propose that a new continental arc was initiated after ca. 190Ma along the coastal region after a magmatic gap due to flat-slab subduction. This newly initiated arc likely persisted until ca. 90Ma, and is represented by the I-type granitic rocks in eastern Taiwan. Slab roll-back likely caused the arc system to retreat towards the Pacific Ocean after 90Ma, and ca. 60–17Ma bimodal magmatism adjacent to the South China Sea signifies continental margin extension in the lead-up to, and during, the opening of the South China Sea. We thus argue that the continental margin of East Asia was transformed from an Andean-type plate margin at 280–90Ma, to the present-day Western Pacific-type plate margin soon after 90Ma.
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► Support the flat-slab subduction model for Mesozoic South China. ► Confirm that a new continental magmatic arc was reinitiated as early as ca. 190Ma. ► Suggest an Andean-type plate margin during 280–90Ma. ► The Western Pacific-type plate margin started soon after ca. 90Ma.
SUMMARY
Anthocyanin is one of the most important pigments and nutrients in fruits. Genes encoding R2R3‐MYB transcription factors (TFs) are key to anthocyanin regulation. R2R3‐MYB activators have been ...widely studied in the anthocyanin synthesis pathway. However, the mechanism by which R2R3‐MYB repressors negatively regulate anthocyanin synthesis remains poorly understood. In the present study, we characterized a subfamily 1 R2R3‐MYB anthocyanin repressor gene, MYB306‐like, from apple (Malus × domestica) and demonstrated its significance in anthocyanin regulation. The MdMYB306‐like protein activates the expression of an anthocyanin repressor gene, MdMYB17, and inhibits the expression of MdDFR (an anthocyanin structural gene) by directly binding to the corresponding promoters. The MdMYB306‐like protein interacts with MdMYB17 and MdbHLH33 through its N‐terminus. In addition, MdMYB306‐like interacts with MdbHLH33 and MdMYB17 to enhance its regulatory activities on MdMYB17 and MdDFR, respectively. Our results revealed that the MdMYB306‐like protein, in conjunction with MdMYB17 and MdbHLH33, forms a key regulatory module to fine‐tune anthocyanin synthesis in apple.
Significance Statement
Subfamily 1 R2R3‐MYB TFs might be a new type of anthocyanin repressor, but there is still some controversy over this possibility. Here, we characterized an anthocyanin repressor gene, MdMYB306, from apple that belongs to the R2R3‐MYB subfamily 1, and revealed the repressive mechanisms for MdMYB306 limiting anthocyanin synthesis at the transcriptional level.
We report here new field and analytical data from Precambrian rocks on Hainan Island of the Cathaysia Block, south China, and examine its probable connection to Laurentia. Granitoids and newly ...discovered felsic volcanic rocks dated at 1433 ± 6 Ma and 1439 ± 9 Ma (SHRIMP U‐Pb zircon) on Hainan Island are coeval with, and isotopically similar to the 1500–1350 Ma trans‐continental granite‐rhyolite province in southern Laurentia. Quartzites unconformably overlying the ca. 1430 Ma volcaniclastic rocks on Hainan Island are interpreted as locally‐sourced Grenvillian foreland basin deposits that can be correlated with the Deer Trail Group of south‐western Laurentia. The detrital provenance of the quartzites contains age populations comparable to the 1610–1490 Ma, westerly‐sourced non‐Laurentian detrital grains reported in the Belt Basin of south‐western Laurentia. Our new data thus make Cathaysia the most likely continental block next to western Laurentia before and during the late Mesoproterozoic assembly of Rodinia.
Adakites, or adakitic rocks, in a broad sense, have been used to describe a large range of igneous rocks with the common feature of high Sr/Y and La/Yb ratios that can be achieved though different ...mechanisms. Among them, the continental, or C-type, adakitic rocks are particularly controversial in terms of their sources and genesis. In this study we revisit both Cu–Au ore-bearing and barren “C-type adakitic rocks” in the Lower Yangtze River Belt (LYRB) of central eastern China, including comprehensive analyses of their in-situ zircon Hf–O isotopes, whole-rock geochemistry and Sr–Nd isotopes. These “C-type adakitic rocks” consist of monzodiorite, granodiorite and quartz monzonite that are classified as shoshonitic to high-K calc-alkaline series according to their chemical compositions. They are characteristically high in potassium (K2O=2.4–4.5%, K2O/Na2O=0.6–1.3), with continental crust-like isotopic compositions, i.e., whole-rock εNd(T)=−3.9 to −7.7, initial 87Sr/86Sr=0.7054–0.7085, zircon εHf(T)=0 to −11, and δ18O=6‰ to 9‰. The ore-bearing and barren rocks are cogenetic. Fractional crystallization of hornblende, titanite, magnetite and apatite played a major role in their chemical variations, with the ore-bearing rocks being more felsic (SiO2=63.3–69.6%) and higher in Sr/Y (41.2–75.6) than the barren rocks (SiO2=57.3–65.0%, Sr/Y=30.4–51.8). All these geochemical and isotopic features, in combination with regional geological data, suggest that the LYRB “C-type adakitic rocks” were unlikely to have been formed by melting of either a thickened and/or delaminated lower continental crust, or an altered oceanic crust as previously thought. These rocks are in general akin in geochemistry and isotopes to the Archean sanukitoids and the Setouchi high-Mg andesites in Japan, and are thus interpreted as being formed by melting of an enriched mantle source metasomatized by dewatering from a delaminated flat-slab. The flat subduction of an oceanic plateau and its subsequent delamination and foundering since the early Mesozoic beneath southeastern China (Li and Li, 2007) thus not only explain the temporal and spatial propagation of widespread Yanshanian igneous rocks regionally since ca. 195Ma, but also the formation of a series of enigmatic “adakitic” rocks in the region, including the LYRB potassium-rich rocks that were inappropriately called the “C-type adakitic rock” by previous workers.
•We revisit China's LYRB “C-type adakites” by Hf–O–Sr–Nd isotopes and geochemistry.•These rocks are potassium-rich monzodiorite, granodiorite and quartz monzonite.•They are derived from an enriched mantle source, not lower crust and oceanic crust.•“C-type adakites” are an inappropriate petrological classification for these rocks.•Delamination of subducted flat-slab accounts for widespread 195–85Ma igneous rocks.
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria ...greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
The Gangbian alkaline complex in the southeastern Yangtze Block (South China) is composed of Si-undersaturated pyroxene syenites and Si-saturated to -oversaturated syenites and quartz monzonites. ...SIMS zircon U–Pb analyses indicate that the complex was emplaced at 848
±
4 Ma, during a previously-recognized interval of magmatic quiescence between the ca 1.0–0.89 Ga Sibaoan orogenic magmatism and the ca 0.83–0.78 Ga magmatic flare-up. The Gangbian rocks are characterized by wide, coherent variations in major and trace elements (SiO
2
=
47.6–68.4%, K
2O
+
Na
2O
=
4.5–10.5%, K
2O/Na
2O
=
0.4–1.2, MgO
=
1.2–8.5%, Cr
=
4.5–239 ppm, and Ni
=
4.5–143 ppm) and by enrichment in LIL and LREE and depletion in Nb, Ta and P in trace element spidergrams. Their whole-rock εNd(
T) (−
6.5 to −
0.4) and εHf(
T) (−
10.7 to 0.4) are positively correlated, suggesting involvement of both metasomatized mantle and continental crust materials in their genesis.
In situ zircon Hf–O isotopic measurements for the most evolved quartz monzonite sample yield a binary mixing trend between the mantle- and supracrustal-derived melts. It is suggested that the pyroxene syenites were derived by partial melting of metasomatized, phlogopite-bearing lithospheric mantle, and the parental magma experienced extensive fractionation of pyroxene and olivine associated with varying degrees of crustal contamination. Subsequent fractional crystallization of hornblende and minor amounts of plagioclase from the alkali basaltic magmas, accompanied by crustal contamination, produced the Si-saturated to -oversaturated syenites and quartz monzonites. These ca. 0.85 Ga alkaline rocks and neighboring contemporaneous dolerite dykes are the products of the anorogenic magmatism after the Sibao Orogeny. They post-date the final amalgamation between the Yangtze and Cathaysia Blocks, most likely manifesting the initial rifting of South China within the Rodinia supercontinent.
SHRIMP U-Pb zircon ages and geochemical and Nd isotopic data are reported for mid-Neoproterozoic igneous rocks in northern Zhejiang Province, South China. The Shenwu dolerite dykes, the Daolinshan ...granite-diabase complex, and the Shangshu bimodal (basalt-rhyolite) volcanic rocks were dated at 849
±
7 Ma, 794
±
9 Ma and 792
±
5 Ma, respectively. All the studied mafic rocks are tholeiitic in compositions and exhibit overall moderate enrichments in most incompatible trace elements, resembling intraplate basaltic rocks in continental rifts. The ∼850 Ma Shenwu dolerites are the earliest anorogenic basaltic rocks identified so far after the ca. 1.1–0.9 Ga Sibao Orogeny, but seem to predate the Neoproterozoic rifting. Our results are clearly at variance with the alternative tectonic model that an active continental margin existed along the southern margin of the Yangtze Block until ca. 800 Ma. The intensive ∼790 Ma bimodal volcanic and plutonic rocks, part of a major phase of mid-Neoproterozoic rifting, are concurrent with the widespread mid-Neoproterozoic intraplate magmatism throughout South China. They are most likely related to the proposed mantle superplume that led to the breakup of the supercontinent Rodinia.
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