Detrital Zircon Age Patterns Research Articles

A Carboniferous to Permian tectono-paleogeographic reconstruction for the southernmost Central Asian Orogenic Belt

The Central Asian Orogenic Belt was formed by the subduction to closure of the Paleo-Asian Ocean (PAO). However, it is highly controversial about the closing time of the PAO, especially its middle segment in the northern Alxa orogenic belt (NAOB). In this study, the new and published zircon U–Pb and Hf data for the Carboniferous to Permian sediments across the NAOB have been integrated to reply the above problem. The depositional ages have been constrained as the Carboniferous to Permian by the detrital zircon ages, fossil assemblages and stratigraphic correlation. The Carboniferous sandstones are dominated by the Paleozoic zircons (mainly around 380–510 Ma) with a few Precambrian zircons. The late Cambrian to early Carboniferous zircons with positive to slightly negative εHf(t) values were probably sourced from the orogen itself. The early Paleozoic zircons with slightly to extremely negative εHf(t) values and the late Archean to Paleoproterozoic zircons were likely derived from the surrounding cratonic blocks in the south. For the Permian samples, the Carboniferous to Permian age signal is enhanced. The Permian zircons yield similar age peaks around 278–279 Ma and similar εHf(t) values, and thus shared a similar source. Thus, the Carboniferous to Permian sediments received detritus across the PAO, indicating the closure of the PAO. Subsequently, the NAOB entered into an extensional setting based on the detrital zircon age patterns, rift-related volcanic rocks and basin analysis. Finally, a tectono-paleogeographic reconstruction from the Carboniferous relic sea and marine transgression to Permian marine regression-transgression-regression with crustal extension was proposed.

Magmatic and sedimentological arguments for an Ediacaran active margin in the Bayankhongor Zone in western Mongolia, Central Asian Orogenic Belt

Geochronological and geochemical investigation of the magmatic and sedimentary rocks from the south-eastern tip of the Bayankhongor Zone (central Mongolia) constrains the Neoproterozoic evolution of the northern margin of the Baidrag Block. There, ultramafic to felsic igneous rocks of the Khan-Uul Massif intruded the volcano-sedimentary sequence of the Ulziit Gol Unit. U–Pb zircon ages show that both the plutonic and volcanic rocks were coeval products of the same Ediacaran (598–564 Ma) magmatism. Most of the samples have low contents of high field strength elements typical of arc-related magmas; however, some mafic rock samples display N-MORB-like chemistry. Magmatic rocks in the Khan-Uul Massif and Ulziit Gol Unit yielded exclusively positive initial εHf in zircon values (+4.9 to +13.8), implying derivation from depleted-mantle sources. Furthermore, heterogeneity of the whole-rock initial εNd values (–4.0 to +2.1) documents that fractional crystallization was accompanied by variable crustal contamination. The detrital zircon age patterns of the sandstone and tuffites in the Ulziit Gol Unit indicate that the sequence was filled dominantly by Ediacaran magmatic detritus derived from the Khan-Uul Massif and its volcanic equivalents, while the older cratonic material from the Baidrag basement represented only a subordinate component. Combined magmatic and sedimentary records imply that both the Khan-Uul Massif and the Ulziit Gol Unit may have formed in the same back-arc basin environment. This challenges the previous view that the entire Bayankhongor Zone was ophiolitic in nature. Distribution of coeval Ediacaran supra-subduction systems on the scale of the Mongolian Collage indicates the closure of multiple oceanic basins rimming the Siberian Continent. Following Rodinia break-up, this peri-Siberian realm was presumably formed by sub-parallel continental ribbons and oceanic basins. It is proposed that the amalgamation of these blocks and closure of intervening oceans reflected the Ediacaran advancing mode of the Palaeo-Pacific subduction.

A fluvial‐aeolian system in response to aridification during the Late Mesozoic, Junggar Basin, Central Asia

AbstractAridification of Central Asia in the Late Mesozoic led to drastic environmental changes characterized by widespread aeolian deposits. We systematically investigated fluvial‐aeolian deposits in the Middle Jurassic Toutunhe Formation, Upper Jurassic Kalazha Formation, and Lower Cretaceous Tugulu Group in the Junggar Basin to the north of the Tianshan Orogenic Belt via unmanned aerial vehicle‐based photogrammetry, scanning electron microscope, grain‐size analysis, and detrital zircon geochronology. Paludal and deltaic environments transitioned to a fluvial‐aeolian environment from the late Middle Jurassic to the Late Jurassic. Fan delta and incisive braided river deposits accumulated in the earliest Cretaceous and evolved into a lacustrine environment with aeolian deposits in the lakeshore. Aeolian deposits are characterized by moderate‐ to well‐sorted and subangular to subround sandstones with large‐scale, high‐dip cross‐bedding, inversely graded lamination, dominant saltation grains, crescent‐shaped, and dish‐shaped impact structures. Aeolian deposits contain heavy minerals including more ilmenite, zircon, garnet, and, tourmaline and less magnetite and epidote than the fluvial deposits. The preserved aeolian sediments of the Kalazha Formation extend west–east for more than 100 km, suggesting a wide desert area during the latest Jurassic. The detrital zircon age patterns indicate that the provenance of the aeolian deposits was similar to that of coeval fluvial deposits. The cooccurrence of fluvial and aeolian deposits and the similar provenances but orthogonal flow directions indicate that the aeolian deposits were mainly sourced from the nearby fluvial material within the basin. The evolution of the fluvial‐aeolian system responded to a complete base‐level cycle controlled by the aridification and tectonics. Due to decreased sediment supply caused by aridification, the base level rose, leading to the change from braided rivers to meandering rivers, along with the deposition of aeolian sediments. Due to the tectonic reactivation in the Late Jurassic, the base level fell, causing the occurrence of alluvial fans and the expansion of the aeolian sediments. Previous studies revealed that the Tianshan in the Jurassic exhibited low relief. The fluvial‐aeolian system played an important role in maintaining the limited relief in southern Central Asia.

U–Pb detrital zircon ages from Cretaceous - Paleogene white sandstone member in Western Tabei Uplift (China) as provenance indicators

The Western Tabei Uplift is one of the largest first-level structural units in the Tarim Basin with great potential for oil and gas resources. Previous studies have established sedimentary provenance of the upper and lower strata in the unconformity of the Cretaceous Bashijiqike Formation and Paleogene Kumugeliemu Group in the Western Tabei Uplift. However, little attention has been paid to the light-colored, white-ish sandstone at the interface of this unconformity, whose sedimentary provenance remains to be investigated. Based on morphology, U–Pb age and trace element analyses of detrital zircon, our study reveals five age peaks in detrital zircon age distribution, ∼300 Ma, ∼420 Ma, ∼820 Ma, ∼1.8–1.9 Ga, ∼2.4 Ga. Potential sources of white sandstone include the Quruqtagh region to the east (E-source), the South Tianshan to the north (N-source), the west of East Tianshan and the north part of Quruqtagh to the north-east (NE-source). Their detrital zircon U–Pb age information is collected and compared with those from the white sandstone. The detrital zircon age comparison demonstrates that the E-source is the primary sedimentary source area for the white sandstone, the N-source may also provide some additional sediments. The detrital zircon age pattern also indicates that the origin of the NE-source is probably supplied by both the E-source and N-source together. Our finding could shed new light on the provenance and sedimentary model of Cretaceous-Paleogene white sandstone member in the Western Tabei Uplift and provide a theoretical basis for further exploration of lithological oil reservoirs in this section.

Locating the Yangtze Block in Nuna: Constraints from age and isotopic data from Paleoproterozoic sedimentary rocks in the Phan Si Pan Zone, northwest Vietnam

New U-Pb ages and Hf isotopic data for detrital zircons from the late Paleoproterozoic sedimentary rocks (Suoi Chieng Formation) in the Phan Si Pan Zone of northwest Vietnam constrain their depositional ages, provenance, and tectonic setting. The weighted average age of the youngest coherent zircon population is 1769 ± 31 Ma (MSWD = 1.3, n = 8), which provides a maximum depositional age for the Suoi Chieng Formation. The detrital zircons obtained from six Paleoproterozoic samples exhibit various ages, showing multiple magmatic and metamorphic events. The detrital zircon age pattern shows that magmatic activities in the source areas occurred at 2650 Ma, 2350–2150 Ma, and 2050 Ma, as well as minor activities at 2850 Ma, 1850 Ma, and 1780 Ma. Additionally, a prominent metamorphic age peak is observed around ca. 1850 Ma, while a few metamorphic zircons exhibit ages ranging from 2600 to 2500 Ma and 2100 Ma. This pattern indicates that the primary source of these zircons is the local basement rocks of the Phan Si Pan Zone and SW Yangtze. However, contributions from other adjoining cratonic blocks are also possible and these likely included the Rae craton of North Laurentia. Our new data verifies and expands earlier results, showing that the SW Yangtze and north Yangtze have distinct Archean-Paleoproterozoic crustal evolutionary histories prior to their assembly in the late Paleoproterozoic. Regional correlations based on detrital zircon spectra, stratigraphic and tectono-thermal histories show strong similarities between the SW Yangtze and the Rae craton of north Laurentia throughout the Paleoproterozoic, suggesting the proximity of the two blocks before or during the formation of the Nuna supercontinent. We further suggest that the north Yangtze adjoined southern Siberia in the Archean to late Paleoproterozoic as supported by their identical tectono-thermal histories and detrital zircon age spectra. In combination with published data, we propose that the Yangtze Block was located between north Laurentia and south Siberia during the Nuna assembly.

Provenance and geotectonic setting of the Paleoproterozoic Cerro Figurita formation (Río de la Plata Craton, Uruguay)

The Cerro Figurita Formation (CFFm) represents a clastic sedimentation approximately 3000 m thick which underwent low greenschist metamorphic conditions. The sedimentary sequence is dominated by polymictic conglomerates and sandstones deposited in an environment of alluvial fans that evolve to marine turbidites. The geochemistry of the CFFm reveals derivation from sources with a mix composition similar to unrecycled Upper Continental Crust; alteration increases towards the top of the sequence (CIA 45–92). The contribution of mafic (probably ophiolitic) source rocks is revealed by petrography and low values of Th/Sc (0.3–1.5), Zr/Sc (6–20), Th/U (3–6) and high values of Cr/V (1.1–12.2); slightly negative Eu/Eu* anomalies (0.7–0.9) would indicate the presence of plagioclase in the source rocks. TDM ages are between 2001 and 2269 Ma, and the ƒSm/Nd values along with the relationship between εNd(t) andTh/Sc ratio indicate a provenance from an andesitic arc component. Detrital zircon age patterns are dominated by 2160, 2163 and 2177 Ma peaks, with the youngest zircon showing an age of 2112 ± 21 Ma, confirming a provenance from the Florida central granitic gneiss belt (FB). It is noteworthy the presence of subordinate populations of detrital zircon grains with ages of 2772, 2935 and 3222 Ma, indicating the presence of an inherited felsic source of Archean age, not yet detected in the Piedra Alta Terrane (PAT), and probably located within the Nico Pérez Terrane. A multi-approach to provenance analyses integrating geochemistry, petrography, U–Pb zircon ages, and Nd isotopes indicate ongoing active tectonism during the Orosirian in the PAT, whereas a retroarc foreland basin geotectonic setting is suggested for the CFFm deposition.

Linking the Paleozoic evolution of Hainan Island to Indochina and Australia: Implication for the paleogeography of the Eastern Tethys Ocean

Paleozoic paleogeographic and tectonic evolution of blocks within the eastern Tethyan Orogenic Belt remains ambiguous due to limited and fragmentary geological records. New detrital zircon U-Pb-Hf isotopic analyses integrated with published data from Paleozoic strata in Hainan Island reveal three significant changes in provenance, providing excellent insights into the assembly record with adjacent blocks. Detrital zircon age spectra of early Cambrian strata from Hainan Island yield a major peak at 1.17 Ga, resembling equivalent units from the Kontum Massif (South Indochina) and were likely sourced from Australia. Mid-late Cambrian successions contain a dominantly 1.78–1.40 Ga zircon population sourced from Precambrian rocks on the island. Detrital zircon age spectra of late Ordovician samples yield major age peaks of 0.97 Ga and 0.45 Ga that originated from India and Indochina, respectively. The two provenance shifts in the Cambrian-Ordovician strata are interpreted to result from the consumption of a branch of the Proto-Tethys associated with progressive amalgamation of the Kontum (South Indochina)-Hainan-Australia block and Truong Son (North Indochina)-India-South China block. The late Devonian-early Carboniferous succession encompass significant ca. 368 Ma zircons derived from arc-related rocks that formed during initial subduction of the main Paleo-Tethys Ocean. The lack of ca. 970 Ma Indian-derived zircons within the Devonian-Carboniferous units suggests that Hainan Island rifted away from Gondwana before the late Devonian. Late Paleozoic detrital zircon age pattern of Hainan Island coincides with that of Indochina and North Qiangtang, but is distinct from that of Gondwana and South China, indicating that the coherent Hainan-Indochina-North Qiangtang continental sliver was separated from Gondwana and South China by the main Paleo-Tethys Ocean and the Ailaoshan Ocean, respectively.

New geochronological results from late Mesoproterozoic to early Neoproterozoic successions in the eastern North China Craton and implications for the reconstruction of Rodinia

Late Stenian to Tonian stratum of the Xihe and Jinxian groups, the Sangwon system, the Penglai Group, the Tumen Group, and the Huaibei and Langan groups located at the eastern margin of the North China Craton provide an excellent record of changes in sediment provenance related to the amalgamation and dispersal of Rodinia and therefore the paleogeographic position of the craton. To decipher their protosource changes over time, we evaluated 7510 U-Pb and 963 Lu-Hf analyses from 92 samples across the entire eastern North China Craton, of which 1746 U-Pb and 415 Lu-Hf analyses from 18 samples are newly reported here. The detrital zircon results indicate two stratigraphic intervals with internally consistent lithostratigraphy, event stratigraphy, biostratigraphy, depositional age, and detrital zircon age patterns: the late Stenian to early Tonian strata and the late Tonian strata, of which the former mainly consists of the Mesoproterozoic detrital zircons with juvenile Hf isotopic features and the latter’s detritus chiefly derived from the Neoarchean to late Paleoproterozoic basement of the North China Craton. In consideration of the paleomagnetic and geochronological data from the coeval strata in other cratons, the Mesoproterozoic detrital zircons of the late Stenian to early Tonian strata are interpreted to be derived from the Musgrave Province in central Australia during the Rodinia amalgamation, and the transition to the autochthonic protosources in the late Tonian possibly indicated the breakup of the North China Craton and North Australian Craton connection.

Two different types of provenances and the amalgamation of subduction complexes in the Eastern Tianshan of the Southern Altaids

The nature and final closure of the northern Tianshan Ocean have been debated in regard to the eastern Tianshan orogen, southern Altaids. The Kanguer subduction complex of the eastern Tianshan is the key to addressing these issues. In this study, we report new mapping, geochemical and geochronological results on the Kanguer subduction complex in the Haluo area. Our new results show that upper Permian (257 Ma) basaltic blocks emplaced in a sandstone matrix in the northern HL area are fragments of normal-mid-ocean-ridge-basalt (N-MORB)-type oceanic crust. The geochronological results indicate that the sandstone matrices display two different types of provenances. The first type in the northern part of the cross-section (till Sample YY12) has maximum depositional ages ranging from 316 Ma to 238 Ma. Their depositional settings varied from intraoceanic island arcs to continental Andean arcs after ca. 244 Ma, their detrital zircon age patterns vary from a single peak to multiple peaks, and their zircon εHf(t) values vary from uniquely high positive to some negative values. The second type is in the southern part of the cross-section with Samples YY12 to 21Kg05, which have the geochemical signatures of continental island arc sandstone, multiple-peak detrital zircon-age patterns, and positive to negative zircon εHf(t) values. The youngest sandstone sample has a maximum depositional age of 241 Ma. The above provenance results indicate that all mélanges and coherent units north of Sample YY12 belong to an accretionary complex of the Dananhu intraoceanic arc, and those south of Sample YY12 belong to an accretionary complex of the Yamansu-central Tianshan arc. According to the youngest components in both accretionary complexes, which suggest the latest subduction events, we conclude that the final amalgamation timing was after 238 Ma and that the Paleo-Asian Ocean closed during the Middle to Late Triassic.

Provenance of Ordovician Malieziken Group, Southwest Tarim and Its Implication on the Paleo-Position of Tarim Block in East Gondwana

Tarim is inferred to have a close connection with East Gondwana during the Ordovician, but the position in East Gondwana remains controversial. In this study, we report 316 detrital zircons U-Pb data from three samples of Ordovician Malieziken Group sedimentary rocks, collected in the Qiate Section, Southwest Tarim, provided new insight into the position of Tarim in East Gondwana. Detrital zircons data indicated the maximum depositional age for the three samples is 489.5 Ma, 478.1 Ma, and 465 Ma, respectively, indicating the Qiate and Kandilike Formation of the Malieziken Group was deposited in Early—Middle Ordovician. The detrital zircons are characterized by two main peaks at ~490 Ma and ~1100 Ma, and three subordinate peaks at ~880 Ma, ~1400 Ma, and ~1650 Ma, suggesting most of the detritus of Malieziken Group from the South Kunlun Terrane (SKT) itself. However, the source of the ~1650 Ma peak is not found in the Tarim block, and the ~1400 Ma and the ~1650 Ma peak are absent in the middle of the three samples, which implied that there is an exotic source. The Paleoproterozoic sediment strata in the Albany–Fraser belt shows dominant peaks at ~1400 Ma and ~1650 Ma may have been transported to SKT and redeposited in the Malieziken Group during the Ordovician. The Malieziken Group shows detrital zircon age patterns resembling those of East Sumatra, Lhasa, and Western Australia which, in combination with the Albany–Fraser belt provenance, enables us to propose that the Tarim block has a close linkage with Western Australia, East Sumatra, and Lhasa in East Gondwana.

Provenance and metamorphism of the Mesoproterozoic Baoyintu Group: Implication for the interaction between the western Central Asian Orogenic Belt and the North China Craton

• The Baoyintu Group was the continental marginal successions deposited after the Mesoproterozoic. • The provenance of the Baoyintu Group shows an affinity with the North China Craton . • The metamorphism of the Baoyintu Group was caused by the interaction between the North China Craton and the Bainaimiao arc. The deposition and metamorphism of the sedimentary rocks are closely related to the tectonic affinity and interactions among different terranes. The metasedimentary Baoyintu Group, which is distributed in the junctional area adjacent to the Alxa Block, the North China Craton (NCC), and the Central Asian Orogenic Belt (CAOB), is an ideal objective to investigate these issues. However, its depositional age, provenance, and metamorphism have not been well studied. To solve these problems, systematic detrital zircon and rutile dating, zircon Hf isotopic analysis, and phase equilibrium modeling were conducted. The youngest detrital zircon age of 1395 ± 32 Ma constrained the maximum depositional age of the Baoyintu Group younger than the Mesoproterozoic. The detrital zircon age pattern and the Hf isotopic data indicate it possessed a similar source to the Langshan Group from the NCC but in contrast to the Alxa Group in the Alxa Block. The peak metamorphic P-T conditions of the Baoyintu Group are 650–660 °C and 12.0–13.6 kbar, which are typical in the Barrovian-type metamorphic belt. Its metamorphic age is confirmed through the rutile dating analysis, which yielded a discordia age of 384 ± 58 Ma. Our synthesized data support the presumption that the Baoyintu Group is the sedimentary series draping on the margin of the northern NCC during the Mesoproterozoic. The metamorphism is involved with the subduction or orogenic process between the NCC and the Bainaimiao arc in the CAOB during the Devonian.

Locating northern Qiangtang on the margin of Gondwana or Laurasia? Evidence from detrital zircon geochronology

• The Permian sandstones of the northern Qiangtang terrane are quite possibly sourced from Gondwana-affinity terranes, such as the southern Qiangtang and Lhasa terranes. • The northern and southern Qiangtang terranes were essentially a unified block during the Late Paleozoic. • The northern Qiangtang terrane was located on the northern margin of Gondwana during the Permian. The relationship between the northern Qiangtang terrane and other blocks in Gondwana and Laurasia continents is still controversial. Here we report U-Pb ages of detrital zircons from the Lower-Middle Permian Nuoribagaribao Formation in the northern Qiangtang terrane, which provides new evidence to constrain the tectonic affinity of the northern Qiangtang terrane during the Late Paleozoic. Sandstones from the middle and upper parts of the Nuoribagaribao Formation contain dominant Ordovician to Devonian (480–360 Ma, peaking at 368 Ma) and Late Paleoproterozoic to Early Mesoproterozoic (1800–1400 Ma, peaking at 1557 Ma) detrital zircons. The U-Pb age spectrum of detrital zircons of them is consistent with those of the Carboniferous strata in the southern Qiangtang and Lhasa terranes to the south; this indicates that rather than being sourced from the Yangtze Block to the east and the Eastern Kunlun-Qaidam-Qilian terrane to the north, the sediments of the Nuoribagaribao Formation were most probably sourced from the Carboniferous strata in the southern Qiangtang and Lhasa terranes to the south or shared the same sources as them. The high similarity of detrital zircon age patterns between the northern and southern Qiangtang terranes, together with other lines of geological evidence, such as paleomagnetism and paleontology, indicate that the northern and southern Qiangtang terranes were essentially a unified block during the Late Paleozoic and were located on the northern margin of Gondwana.

New detrital zircon geochronological results from the Meso-Neoproterozoic sandstones in the southern-eastern Liaoning region, North China craton, and their paleogeographic implications

We present new detrital zircon U–Pb and Hf isotopic dating results from the late Mesoproterozoic to early Neoproterozoic sandstones exposed in the southern-eastern Liaoning Province, eastern North China craton (NCC). The Qiaotou Formation (Fm) in the Benxi and Dalian regions yield similar detrital zircon age patterns characterized by peaks around ∼1750 Ma, ∼1600 Ma, ∼1175 Ma and ∼1100 Ma. The Kangjia Fm in the Benxi region and the Changlingzi Fm in the Dalian region share similar detrital zircon age patterns, which in combination with their similarities in stratigraphic sequences and lithologic associations, suggest that they are correlative rock units. Based on the detrital zircon dating results and U–Pb ages of mafic sills intruding the strata, we suggest that the Qiaotou Fm is younger than ∼1077 Ma and older than ∼948 Ma, and the age of the Kangjia and Changlingzi formations is between ∼1111 Ma and ∼924 Ma. We synthesize the new data with detrital zircon age and Hf isotopic data reported in the region and other Meso-Neoproterozoic basins in the eastern NCC and suggest that Grenville-age (∼1300–1000 Ma) detrital zircons widely discovered in those strata might be transformed from other cratons. The possibility that those non-NCC provenance detrital zircons might be sourced from the Baltica, São Francisco–Congo and Laurentia cratons existed. But the former two solutions that the NCC directly connected to either of those cratons are contradictory to the global paleogeographic reconstruction context of supercontinent Rodinia. The Grenvillian and Sveconorwegian orogenic belts on Laurentia–Baltica conjoined continents are more likely the sediment provenance of non-NCC Grenville-age detrital zircon provenance in the Meso-Neoproterozoic basins in eastern NCC in the configuration context of the possible NCC–NW Laurentia conjugation in Rodinia.

Detrital zircon geochronology and heavy mineral composition constraints on provenance evolution in the western Pearl River Mouth basin, northern south China sea: A source to sink approach

Investigating the provenance evolution of sedimentary basins with complex tectonic histories is challenging because of the continuously evolving tectonic framework and changing source areas. Pearl River Mouth Basin (PRMB) in the northern South China Sea preserves a large volume of Cenozoic sediments derived from both intrabasinal and extrabasinal sources. However, rare study has been conducted to investigate the provenance evolution of the western PRMB. In this study, we report new detrital zircon U–Pb geochronological and heavy mineral data from the western PRMB, attempting to identify its potential sources and provenance evolution from Eocene to early Miocene. Our data from distinct structural units and formations reveal spatial-temporal differences in provenance. In the northern part, a similar age pattern with a major peak at ∼425 Ma and a subordinate peak at ∼230 Ma is preserved in the Eocene-late Oligocene sediments and suggests that sediments were mainly derived from the Yunkai Massif via Nanduhe River. By contrast, in the southern part, the Eocene-late Oligocene sediments display a dominant age population ranging from 100 Ma to 300 Ma, which implies that the sediments were mainly eroded from nearby Shenhu Uplift and Hainan Island. The heavy mineral data also record such spatial differences in provenance. However, during the early Miocene, the northern and southern parts show similar detrital zircon age patterns with multiple clusters at ∼245 Ma, ∼450 Ma, ∼850 Ma, 970–980 Ma, 1825–1845 Ma, and ∼2500 Ma, indicating that the Miocene sediments across the whole basin were mainly provided by the Pearl River system. The increase of Paleozoic and Precambrian zircons in the lower Miocene sediments suggests a profound provenance shift from multiple nearby sources to the South China Block via the Pearl River between Oligocene and Miocene in the western PRMB, and its timing is posterior to other regions of the PRMB. Finally, four-stage source-to-sink evolution for the PRMB is proposed, showing that sediment provenance in the PRMB is controlled by regional tectonic movement, drainage evolution, and basin architecture. This study suggests that the small-scale drainage system Nanduhe River sourced by Yunkai Massif contributed significantly to the PRMB between Eocene and Oligocene, and highlights its complex processes of provenance evolution that are relevant to the evolution of marginal sea basins globally.

Archean and Paleoproterozoic zircons in Paleozoic sandstones in southern New Zealand: evidence for remnant Nuna supercontinent and Ur continent rocks within Zealandia

Detrital zircon age patterns are reported from quartz sandstones and metaquartzites in the Russet and Wangapeka formations (Western Province, Takaka Terrane) in Fiordland and northwest Nelson, and the Pegasus Group on Stewart Island. The latter indicate a possible maximum early Carboniferous depositional age with a significant Lower Devonian zircon component that suggests a source on the Campbell Plateau or Marie Byrd Land, West Antarctica. In contrast, Russet Formation ages indicate a correlation with Upper Ordovician, Wangapeka Formation quartz sandstones in northwest Nelson. These zircon age patterns have two major groups: late Mesoproterozoic (1200–1000 Ma) of Rodinia origin and Cambrian–late Neoproterozoic (700–500 Ma) of early Gondwana derivation. Both groups have local Zealandia provenances. In addition, there are unusually high proportions (to 20%) of early Paleoproterozoic and Archean zircons, 3500–2000 Ma, with significant age components, 2550–2450 Ma and ca 2800 and 2650 Ma, which are characteristic of an Expanded-Ur continent. Their high proportions of euhedral grains indicate a local source within a postulated Archean basement block at or near the eastern margin of the Takaka Terrane. A proposed Rodinia supercontinent reconstruction locates this Precambrian basement as a Zealandia component placed between Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton. KEY POINTS Pegasus Group, metaquartzites, Stewart Island are not correlated with the Russet Formation, Fiordland but are an Upper Devonian or lower Carboniferous sedimentary unit. Russet Formation high-grade metasandstones in Fiordland are correlated with the lower-grade and fossiliferous Upper Ordovician Wangapeka Formation in Nelson. Upper Ordovician sandstones in Western Province, New Zealand contain unusually high proportions of Neoarchean euhedral detrital zircons that suggest a local Zealandia source. An Archean block is proposed within the Rodinia supercontinent, between the Gawler and North Australia cratons of Australia and Yangtze Block of the South China Craton.

Jurassic subduction of the Paleo-Pacific plate in Southeast Asia: New insights from the igneous and sedimentary rocks in West Borneo

The tectonic affinity of West Borneo and its relationship with the East Asia continental margin are key issues for unraveling SE Asia tectonics. New zircon U-Pb and Hf-O isotopes and whole-rock elemental and Sr-Nd-Pb isotopic data of the igneous and associated sedimentary rocks in West Borneo document the development of Early (∼200–185 Ma) and Late (∼160–145 Ma) Jurassic arc-like igneous rocks. In the Kuching Zone and South Schwaner Mountains, the Jurassic mafic-intermediate igneous rocks are characterized by enrichment in LILEs, depletion in HFSEs, εHf(t) = +0.6 – +11.6, δ18O = 4.97–5.61‰, εNd(t) = −2.5∼+2.4, (206Pb/204Pb)i = 18.71–19.37 and (208Pb/204Pb)i = 38.75–39.58. They originated from a sediment-modified mantle wedge source in a supra-subduction zone setting. The Jurassic granitoids shared consistent elemental and Sr-Nd-Pb-Hf-O isotopic signatures with εHf(t) = +1.7∼ +15.6, δ18O = 4.97–6.01‰, εNd(t) = −1.1 ∼ +4.2, with Δ8/4 = 22.5–51.9 and Δ7/4 = 5.8–14.3, arguing for a juvenile crust-dominated origin. Detritus from the associated sedimentary rocks in the Kuching Zone and South Schwaner Mountains was largely derived from the nearby Jurassic magmatic arc. Their detrital zircon age patterns are comparable to those from the East Malaysia-Indochina and Sibu zone, but distinctive from those in SE Borneo. Integrating all data with those from regional surveys, the igneous and sedimentary rocks in the South Schwaner Mountains are suggested to commence in the earliest Jurassic or even Triassic. West Borneo might be the eastward extension of the Triassic Sundaland. The western Kuching Zone and western South Schwaner Mountains represent the southmost part of the active Jurassic Andean-type East Asian continental margin. The westward subduction of the paleo-Pacific plate was initiated around the earliest Jurassic at ∼200 Ma or earlier.

U–Pb geochronology of Upper Triassic – Lower Jurassic detrital sequences from SE margin of the South China Block: implications for Palaeo-Pacific subduction and tectonic evolution

AbstractWe performed U–Pb dating of detrital zircons and conducted petrological and whole-rock geochemical analyses to assess the provenance of the Upper Triassic – Lower Jurassic clastic rocks in the southeastern margin of the South China Block. Detrital zircon U–Pb ages are mainly classified into age groups of 2000–1700, 900–700, 490–390 and 280–210 Ma, consistent with derivation from the Jiangnan orogenic belt, Nanling Belt, as well as Wuyi and Yunkai domains. Lower Jurassic samples yield a special main age population of 200–190 Ma, and these detrital zircon grains have low Th/U and Nb/Hf ratios and high Th/Nb and Hf/Th ratios, showing they are derived from a continental magmatic arc. However, the cross-correlation and likeness coefficients of kernel density estimates of Upper Triassic and Lower Jurassic sandstones are 0.8608 and 0.8403, indicating that their populations are highly similar. Since the tectonic setting is the key factor in controlling the relationship between source and sink, the stable supply of identical provenance suggests that the tectonic setting did not significantly change during Late Triassic – Early Jurassic time. Sandstone petrography, regional facies distribution and the detrital zircon age patterns all reflect a consistent tectonic setting for the South China Block during Late Triassic – Early Jurassic time. The Palaeo-Pacific subduction therefore did not control the tectonic evolution of the South China Block until after the Early Jurassic Epoch.

Gaining from loss: Detrital zircon source-normalized α-dose discriminates first- versus multi-cycle grain histories

Detrital zircon U–Pb ages are widely employed as an archive of geological processes through time. Changes in detrital zircon age patterns within sediments reflect changes in source areas that are often related to tectonic and/or climatic processes. However, discrimination of first-cycle and multi-cycle detrital zircon with primary crystalline and secondary sedimentary sources, respectively, can be challenging using only crystallisation age constraints. Here, we present U–Pb geochronology of detrital zircon from modern fluvial and littoral environments on the Scott Coastal Plain in Western Australia to investigate the use of α-dose to identify sedimentary recycling. The majority of 1032 concordant U–Pb ages are interpreted to be ultimately sourced from the local basement. However, U–Pb ages do not reflect the areal extent of source rocks and indicate significant reworking of coastal plain sediments. A novel metric – source-normalized α-dose – demonstrates predominant detrital zircon routing via recycling through intermediate storage. This metric is defined as the ratio of the average α-dose (a measure of metamictization) of detrital zircon belonging to a characteristic age group and the average α-dose of zircon grains within the corresponding source crystalline basement. Average values of source-normalized α-dose of detrital zircon populations <1 are interpreted to reflect selective removal of more labile (metamict) grains via attrition and diagenesis, indicating greater grain transport and recycling, whereas values of c. 1 signify shorter transport and a first-cycle origin. Application of this approach to ancient clastic systems is supported by consistency of results with independent indicators of progressive sedimentary recycling and/or transport. Source-normalized α-dose is an internal measure using zircon grain chemistry (U and Th), and avoids bias associated with multi-mineral measures of sediment recycling that may be related to source fertility. Additionally, source-normalized α-dose uses measures typically captured during routine U–Pb geochronology. Source-normalized α-dose of detrital zircon provides an additional method to address sedimentary source-to-sink transport and recycling, and ultimately allows more robust interpretation of U–Pb zircon data.

The Maz Metasedimentary Series (Western Sierras Pampeanas, Argentina). A relict basin of the Columbia supercontinent?

AbstractThe Maz Metasedimentary Series is part of the Maz Complex that crops out in the sierras of Maz and Espinal (Western Sierras Pampeanas) and in the Sierra de Umango (Andean Frontal Cordillera), northwestern Argentina. The Maz Complex is found within a thrust stack of Silurian age, which later underwent open folding. The Maz Metasedimentary Series mainly consists of medium-grade garnet–staurolite–kyanite–sillimanite schists and quartzites, with minor amounts of marble and calc-silicate rocks. Transposed metadacite dykes have been recognized along with amphibolites, metagabbros, metadiorites and orthogneisses. Schist, quartzite and metadacite samples were analysed for SHRIMP U–Pb zircon dating. The Maz Metasedimentary Series is polymetamorphic and records probably three metamorphic events during the Grenvillian orogeny, at c. 1235, 1155 and 1035 Ma, and a younger metamorphism at c. 440–420 Ma resulting from reactivation during the Famatinian orogeny. The sedimentary protoliths were deposited between 1.86 and 1.33–1.26 Ga (the age of the Andean-type Grenvillian magmatism recorded in the Maz Complex), and probably before 1.75 Ga. The main source areas correspond to Palaeoproterozoic and, to a lesser magnitude, Meso-Neoarchaean rocks. The probable depositional age and the detrital zircon age pattern suggest that the Maz Metasedimentary Series was laid down in a basin of the Columbia supercontinent, mainly accreted between 2.1 and 1.8 Ga. The sedimentary sources were diverse, and we hypothesize that deposition took place before Columbia broke up. The Rio Apa block, and the Río de la Plata, Amazonia and proto-Kalahari cratons, which have nearby locations in the palaeogeographic reconstructions, were probably the main blocks that supplied sediments to this basin.

Model versus measured detrital zircon age signatures of the early Earth

The scarcity of Archean (4.0–2.5 Ga) rocks on Earth limits our ability to analyse when plate tectonics began and what tectonic mode may have preceded it. Proposed times for the initiation of plate tectonics range from the Hadean eon (>4 Ga) to the Neoproterozoic era (ca 1.0–0.5 Ga), before which the Earth may have been dominated by stagnant-lid regimes that cooled through volcanic advection, partial crustal convection, and/or conduction. Here, we use various 1D numerical simulations of potential geodynamic states of the early Earth to predict detrital zircon age patterns. We find that different Archean tectonic modes yield contrasting temporal differences between zircon crystallization ages and respective maximum depositional ages of the sediments from which the detrital zircons were sourced (we have termed such age differences ‘ΔtDZ’). We compare these predictions with a global compilation of detrital zircon age data from >400 Archean (meta)sedimentary units, including new data from six samples from the Pilbara Craton, Western Australia. Combined, the data show significantly increased contributions from high ΔtDZ detrital zircons after ca 3.4 Ga. For the Pilbara Craton, 90% of the detrital zircons in each of two >3.4 billion-year-old metasedimentary samples have crystallization ages that are ≤110 million years older than the maximum age of deposition (we use ‘ΔtDZ90’ to denote such age differences hereafter). The ΔtDZ90 of Pilbara strata formed at ca 3.29–3.27, 3.24–3.18 and ca 2.95 Ga show successively larger ΔtDZ90 values of ca 270, 290 and 570 million years, respectively. Globally, pre-3.4 billion-year-old samples show a low mean ΔtDZ90 of around 70 million years, but a mean of around 320 million years for 3.40–2.80 billion-year-old samples. Samples with >90% of zircons featuring >250 million year ΔtDZ values only occur at or after ca 3.23 Ga. These results are consistent with a significant slow-down in the rate of volcanic resurfacing, and increasing contributions of detritus from basins associated with exhumation and/or volcanic quiescence after ca 3.4 Ga. Compared with detrital zircon age predictions, our findings are best explained by a transition from volcanism-dominated stagnant-lid modes to one increasingly dominated by subduction over the period 3.4–3.2 Ga, with the emergence of plate tectonics within this period or at some time thereafter.