Pb Detrital Zircon Geochronology Research Articles

Mineral chemical and geochronological constraints on the age and provenance of the eastern Circum-Rhodope Belt low-grade metasedimentary rocks, NE Greece

In north-eastern Greece the mid-greenschist facies Makri Unit and the anchizonal Melia Formation belong to the eastern Circum-Rhodope Belt that forms the uppermost tectonostratigraphic unit of the Rhodope metamorphic nappe pile. The two metasedimentary successions had different source areas, although they now lie in close proximity in the Rhodope Massif. The U–Pb isotopic ages of detrital zircons from a metasandstone of the Makri Unit analysed using LA–SF–ICP–MS and SHRIMP-II gave age clusters at ca. 310–290 Ma and at ca. 240 Ma for magmatic zircons, which may have been derived from Carboniferous–Permian basement rocks of the Thracia Terrane (Lower Tectonic Unit of the Rhodope Massif) that subsequently underwent Triassic rifting. The youngest detrital zircon grains found so far indicate that the metasedimentary succession of the Makri Unit, or at least parts of it, cannot be older than Late Triassic. By contrast, clastic sedimentary rocks of the Melia Formation contain the primary detrital mineral assemblage of epidote, zoisite, garnet, and phengitic mica, which is absent in the Makri Unit, and clearly points to metamorphic rocks being the major source for these sediments. U–Pb analyses of detrital zircons gave a prominent age cluster at ca. 315–285 Ma for magmatic zircons. Inherited cores indicate the involvement of Pan-African and Late Ordovician–Early Silurian crustal sources during Late Carboniferous–Early Permian igneous event(s). Moreover, U–Pb detrital zircon geochronology indicates that the Melia Formation cannot be older than latest Middle Jurassic. We suggest that the Melia Formation was deposited in front of a metamorphic nappe pile with Rhodopean affinities in Tithonian or Cretaceous times. Both the Makri Unit and the Melia Formation have been tectonically juxtaposed from different sources to their present location during Balkan and Alpine orogenic processes.

Tracing the position of the South China block in Gondwana: U–Pb ages and Hf isotopes of Devonian detrital zircons

U–Pb detrital zircon geochronology from Lower Devonian quartz arenites of the northwestern margin of the Yangtze block yields dominant early Neoproterozoic (0.85–1.0 Ga), Pan-African (0.5–0.65 Ga) and middle Neoproterozoic (0.68–0.8 Ga) age populations and minor Mesoproterozoic to middle Mesoarchean (1.0–3.0 Ga) ages. Middle Mesoarchean to Mesoproterozoic rocks, however, are widespread in the South China block. Although Hf isotopic compositions show both juvenile crustal growth and crustal reworking for all the age groupings, the crust growth, essentially mantle-derived, occurred mainly around 3.1 Ga, 1.9 Ga and 1.0 Ga, respectively. Zircon typology and youngest grain ages indicate that this suite of quartz arenites was the product of multiphase reworking. Abundant magmatic zircon detritus with concordant U–Pb Grenvillian and Pan-African ages, together with accompanying various ε Hf( t) values, indicate an exotic provenance for the quartz arenite external to the South China block. Qualitative comparisons of age spectra for the late Neoproterozoic sediments of the Cathaysian Block, early Paleozoic sediments of pre-rift Tethyan Himalaya sequence in North India and lower Paleozoic sandstone from the Perth Basin in West Australia, show that they all have two the largest age clusters representing Grenvillian and Pan-African orogenic episodes. The resemblance of these age spectra and zircon typology suggests that the most likely source for the Lower Devonian quartz arenites of the South China block was the East African Orogen and Kuunga Orogen for their early Grenvillian and Pan-African populations, whereas the Hannan–Panxi arc, Jiangnan orogen, and the Yangtze block basements might have contributed to the detrital zircon grains of the Neoproterozoic and Pre-Grenvillian ages. Hf isotopic data indicate that the crustal evolution of the drainage area matches well with the episodic crust generation of Gondwana. These results imply that the previously suggested position of the SCB in Gondwana should be re-evaluated, and the South China block should be linked with North India and West Australia as a part of East Gondwana during the assembly of Gondwana, rather than a discrete continent block in the paleo-Pacific.

U/Pb detrital zircon provenance from late cretaceous metamorphic units of the Guajira Peninsula, Colombia: Tectonic implications on the collision between the Caribbean arc and the South American margin

Abstract Mesozoic metamorphic units exposed along the northern margin of the South American plate record the different stages of subduction evolution or arc-continent collision between the margins of the Caribbean plate and the South American continent. U–Pb detrital zircon geochronology for provenance analysis was carried out on meta-sedimentary rocks of the Etpana formation and metamorphic boulders found within a nearby Tertiary conglomerate, including high-pressure rocks in the Colombian Caribbean. All samples have similar age populations, suggesting that they share a relatively common source and paleogeography. Prominent age peaks include Meso and Paleoproterozoic ages of ca. 1624 Ma and 1315 Ma, Cambrian to Neoproterozoic ages of ca. 630 Ma, 580 Ma and 547 Ma, and less abundant Jurassic and Permian ages of ca. 270 Ma and 160 Ma, which indicate that the South American margin is a major source for the sedimentary protoliths. There are also remnants of younger Cretaceous allocthonous Caribbean arc input at ca. 90–70 Ma. The deposition and metamorphism of these units records the ongoing Late Cretaceous continental subduction of the South American margin within the Caribbean intra-oceanic arc-subduction zone. This gave way to an arc-continent collision between the Caribbean and the South American plates, and sediments with continental signatures were incorporated into the subduction channel and the accretionary wedge. As convergence continued, sediments derived from a mix of South American and arc sources were deposited and included in the collisional wedge up until

Provenance and U–Pb geochronology of the Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, and its tectonic significance

The Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, is a 2.8 km thick clastic sedimentary sequence deposited in a continental basin closely related to volcanic activity. It consists of three formations: the Pozo Duro (oldest), the Anita, and the Escalante (youngest). Petrographic study, conglomerate pebble counts, and U–Pb geochronology of detrital zircons were performed to determine the source and age of this sequence, and to interpret its tectonic setting. In the sandstones of all three formations, the most abundant grains are those of volcanic composition (Q38F22L40, Q35F19L46, and Q31F22L47, respectively). The Pozo Duro Formation includes well-rounded quartz-arenite clast conglomerates, whereas conglomerates of the two upper units have clasts predominantly of andesitic and rhyolitic composition. The most likely source for these sediments was the Jurassic volcanic arc exposed in northern Sonora and southern Arizona. Zircons from five sandstone samples define two main age groups, Proterozoic and Mesozoic. The first ranges mostly from 1000 to 1800 Ma, which suggests the influence of a cratonic source. This zircon suite is interpreted to be recycled and derived from the same source area as the quartz-rich sandstone clasts in the basal part of the section. Mesozoic zircons range from Triassic to Late Cretaceous, which confirms the proposed Late Cretaceous age for the sequence, and also corroborates Jurassic felsic source rocks. Another possible source was the Alisitos volcanic arc, exposed along the western margin of the Baja California Peninsula. Of regional significance is the great similarity between the El Chanate Group and the McCoy Mountains Formation of southeastern California and southwestern Arizona. Both are Cretaceous, were deposited in continental environments, and have similar zircon-age patterns. Also, both exhibit intense deformation and locally display penetrative foliation. These features strongly suggest that both units underwent similar tectonic histories.

Provenance of intra-Rodinian basin-fills: The lower Dalradian Supergroup, Scotland

Scotland occupied a unique position within the Neoproterozoic supercontinent Rodinia, lying close to the junction of Laurentian, Amazonian and Baltican continental blocks. During the attempted break-up of the supercontinent, a series of intracratonic rift basins were created along the Scottish sector of the future Laurentian margin. These basins were filled with the thick, siliciclasitc Torridonian, Moine and Dalradian Supergroups. Combined U–Pb detrital zircon geochronology and Nd-isotope analyses of whole rocks are used to compare the provenance of two contemporaneous lower Dalradian rift basin-fills. The main control on their provenance signature is sedimentary transport direction, which allows the relative palaeogeographical positions of surrounding basement terranes to be assessed. Westerly derived sedimentary systems supplied voluminous ca. 1.8 Ga aged detritus to the western Corrieyairack Basin. By contrast, sediment supplied from the east within the eastern Strathtummel Basin was dominated by ca. 0.9–1.0 Ga sources. Distal and further travelled basin-axial depositional systems supplied the basins with a greater variety of detritus, dominated by early Mesoproterozoic (1.4–1.6 Ga) and late Palaeoproterozoic (1.6–1.8 Ga) ages. The dataset is consistent with the lower Dalradian Supergroup being sourced from the eastern Laurentian (Labrador region) and/or possibly western Baltica blocks. These data indicate that the basins were flanked to the west by ca. 1.8 Ga Makkovikian-Ketilidian (Rhinnian) igneous basement and to the east by 1.0 Ga Grenvillian-Sveconorwegian basement. This interpretation, combined with the similarities with other penecontemporaneous Laurentian rift-basin fills, indicates that the Dalradian Supergroup is not allochthonous or exotic to the Laurentian continental block.

The source of gold for the witwatersrand from Re–Os and U–Pb detrital zircon geochronology

The source of gold for the witwatersrand from Re–Os and U–Pb detrital zircon geochronology

U–Th–Pb detrital zircon geochronology from the southern Prince Charles Mountains, East Antarctica—Defining the Archaean to Neoproterozoic Ruker Province

Laser ablation inductively coupled mass spectrometry (LA-ICPMS) dating of detrital zircon has been employed to tighten geochronological constraints from the southern Prince Charles Mountains, East Antarctica. The grains of detrital zircon are from extensive metasedimentary units that define different stratigraphic levels. Provenance information from this study has identified three lithostratigraphic units that range in age from Archaean to Neoproterozoic times. The newly defined Tingey Complex contains the oldest known strata, and consists of an Archaean felsic basement overlain by three stratigraphic layers, distinguished by ca. 3200 Ma, ca. 2800 Ma and ca. 2500 Ma detrital zircon grains. The Lambert Complex consists of a metasedimentary package, characterised by ca. 2100 Ma, ca. 1900–1800 Ma and ca. 2600 Ma detrital zircon grains that possibly overlies late Palaeoproterozoic orthogneiss. The Neoproterozoic Sodruzhestvo Group comprises the youngest exposed unit and consists of a thick, clastic-dominated sequence that is distinguished by ca. 1170–970 Ma grains. This study suggests that the isotopic differences reported from the southern Prince Charles Mountains are a result of stratigraphic stacking, rather than due to juxtaposition via collision and accretion tectonics. The discovery of ca. 2500 Ma detrital zircon grains within the Palaeoproterozoic metasedimentary rocks of the Tingey Complex strengthens correlations with Archaean fragments exposed in neighbouring regions of East Antarctica. Constraining the deposition of the Sodruzhestvo Group to the mid-Neoproterozoic period suggests a prominent period of basin development occurred within the southern Prince Charles Mountains at this time.

LA-ICP-MS U–Pb geochronology of detrital zircons from the Jining Complex, North China Craton and its tectonic significance

LA-ICP-MS U–Pb zircon dating and cathodoluminescene (CL) image analysis were carried out to determine the protolith and metamorphic ages of high-grade Al-rich gneisses, named as “khondalites”, from the Jining Complex of the North China Craton (NCC). The analytical results of more than 200 detrital zircon grains from the khondalites show three main age populations: 2060 Ma, 1940 Ma and 1890 Ma. These data indicate that the provenance of the Jining khondalites is Paleoproterozoic in age, but not Archean as previously suggested, and the sediments were derived from a provenance different from the Eastern Block and the Yinshan Terrane of the NCC. The nearly concordant youngest age of 1842 ± 16 Ma ( 207Pb/ 206Pb age) for the detrital zircons is interpreted as the maximum depositional age of the khondalites. Overgrowth rims of detrital zircons yield an age of 1811 ± 23 Ma, which we interpret as the metamorphic age. The new age data are consistent with the recent three-fold tectonic subdivision of the NCC and support that the Eastern and Western Blocks collided at ∼1.8 Ga to form the coherent NCC.

SHRIMP U–Pb geochronology of detrital zircons from the Treasure Lake Group — new evidence for Paleoproterozoic collisional tectonics in the southern Hottah terrane, northwestern Canadian Shield

The recently defined Treasure Lake Group is a platformal sedimentary sequence more than 3 km thick that was deformed and metamorphosed prior to formation of the Great Bear continental arc during 1875–1845 Ma. The group is exposed as remnants in the southern part of the arc. Its basement is not exposed, but is interpreted to comprise the Paleoproterozoic Hottah terrane, which is exposed at Hottah Lake in the northern part of the arc. Studies in that region show that the Hottah terrane collided with the Archean Slave craton to the east ca. 1883 Ma following reversal of subduction polarity from west to east. Continued eastward subduction under the collision zone formed the Great Bear arc. The present study was undertaken to determine the age and provenance of the Treasure Lake Group. Thirty-nine detrital zircon grains from a sample of a quartz arenite unit in the middle part of the Treasure Lake Group were analyzed by SHRIMP (sensitive high-resolution ion microprobe). They show an age range from ca. 2729 to ca. 1880 Ma, with main modes at ca. 1895, 1985, 2090, and 2330 Ma. These data confirm a mainly Paleoproterozoic provenance for the group. The youngest group of five zircon analyses places the maximum depositional age at 1886 ± 8 Ma. The Treasure Lake Group is close to the north-trending Wopmay medial zone formed during collision of the Hottah terrane and the Slave craton. Deformation and metamorphism of the group can now be attributed to the collisional event. The group may in part be coeval with the Bell Island Bay and Akaitcho groups of the northern Hottah terrane, the lower parts of which were deposited ca. 1900 Ma. The wide range of detrital zircons ages found in this study is interpreted to reflect a complex Paleoproterozoic evolution of the Hottah terrane.

U–Pb geochronology of detrital zircons in metasedimentary rocks from southern Baffin Island: implications for the Paleoproterozoic tectonic evolution of Northeastern Laurentia

A geochronological investigation of metasedimentary rocks from southern Baffin Island using the Geological Survey of Canada SHRIMP II (sensitive high-resolution ion microprobe) has characterized the ages of detrital zircon populations to determine their provenance, bracket timing of deposition, and distinguish potentially distinct sequences of rocks. Four lithologically and structurally distinct metasedimentary packages have been identified; each appears to have been derived from a different source region. In the structurally lowest package, all analysed zircons are Archean, and > 90% have ages between 2.83 and 2.63 Ga; these rocks are interpreted as the northernmost exposures of the Paleoproterozoic Povungnituk Group of the Cape Smith Belt, northern Quebec, with detritus derived from the Superior craton. Occupying the intermediate structural levels, the most abundant supracrustal rocks on southern Baffin Island are siliciclastic and carbonate units of the Lake Harbour Group, and the Tasiuyak paragneiss. Five samples show a dominantly Paleoproterozoic signature (2.2–1.9 Ga), with only rare Archean zircons; the provenance of this detritus is uncertain. In the distinct package of feldspathic quartzite and pelite that stratigraphically overlies the Lake Harbour Group, all of the analysed detrital grains are Archean, ~80% are > 2.83 Ga, with a small proportion of the grains in excess of 3.0 Ga; all of this material is thought to be derived from the Archean craton exposed on the Hall Peninsula east of the study area. Finally, at the highest structural level, a sample associated with the Hall Peninsula orthogneisses contains zircons with prominent modes at 2.92, 2.82, and 2.77 Ga, consistent with derivation from the surrounding orthogneisses.

Sedimentary evolution of the Riphean–Vendian basin of southeastern Siberia

The Riphean to Vendian ( ≈1600–540 Ma) sedimentary succession of the southeastern margin of the Siberian platform is 12–14 km thick and consists of terrigenous-carbonate successions termed, from oldest to youngest, the Uchur, Aimchan, Kerpyl, Lakhanda, Uy and Yudoma Groups. Group boundaries typically are regional unconformities; local angular unconformities occur at the base of the Aimchan and Yudoma Groups. Deposition mostly occurred in terrestrial to shallow marine sedimentary environments; only the Uy Group contains evidence of deep-water sedimentation. Paleocurrent and facies trends show that provenance of the Uchur, Aimchan and most of Kerpyl Groups was from the Siberian craton to the west. This corresponds with the mineralogical and chemical composition of sandstones, which suggests continental block to recycled orogen provenance with predominance of granites in the source area. Sandstones from the Uy and Yudoma Groups were derived from both western (Siberian) and eastern (non-Siberian) sources. The Uy Group contains graywacke that implies local recycled orogen to arc orogen provenance. Trace and rare earth element geochemistry suggests provenance from post-Archean source rocks and this is supported by U–Pb detrital zircon geochronology which indicates that only 3 of the 96 grains analyzed are of Archean age. Detrital zircons ≈2050 Ma predominate at the base of the Uchur Group. At the base of the Kerpyl Group ≈2060–1880 Ma zircons predominate with youngest grains ≈1300 Ma. The latter represents an unknown source, as rocks younger ≈1700 Ma are not reported from the basement of the Siberian platform. Zircons in the uppermost part of the Uy Group range in age from 1500 to 1050 Ma suggesting a non-Siberian provenance, perhaps from the Grenville orogen of Laurentia. Conventional U–Pb analysis of a few detrital zircon grains from the Yudoma Group sandstones yielded ages ≈2200–2000. Sedimentological and stratigraphic studies indicate that the Riphean–Vendian sedimentary basin of southeastern Siberia initiated by rifting that subsequently failed, allowing the development of a long-lived intracratonic sedimentary basin. Mafic magmatism and depositional features of the Uy Group suggest that there was renewed rifting ≈1000 Ma, when the basin evolved into an aulacogen. Rifted arms spread to form the Verkhoyansk ocean, the margins of which were approximately parallel to the modern margin of Siberian platform and Okhotsk massif.

U–Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska

Metamorphic rocks within and west of the northern Coast Mountains in southeastern Alaska consist of an Upper Proterozoic(?) to upper Paleozoic continental margin assemblage that we interpret to belong to the Yukon-Tanana terrane. U–Pb geochronologic analyses of single detrital zircon grains from four samples of quartzite suggest that the zircons were shed from source regions containing rocks of ~495 Ma, ~750 Ma, 1.05–1.40 Ga, 1.75–2.00 Ga, ~2.3 Ga, 2.5–2.7 Ga, and ~3.0 Ga. Multigrain fractions from two samples yield upper intercepts between 2.0 and 2.3 Ga, but the scarcity of single grains of similar age suggests that these fractions comprise a mixture of < 2.0 and > 2.3 Ga grains. Zircons in these rocks generally overlap in age with (i) detrital zircons in metasedimentary rocks of the Yukon–Tanana terrane in eastern Alaska and Yukon, (ii) detrital zircons in strata of the Cordilleran miogeocline, and (iii) plutonic and gneissic rocks that intrude or are overlain by miogeoclinal strata. In addition, the pre-1.7 Ga grains overlap in age with dated crystalline rocks of the western Canadian Shield. These similarities raise the possibility that metaclastic rocks in the northern Coast Mountains accumulated in proximity to western North America. The younger zircon populations were likely shed from mid-Proterozoic to early Paleozoic igneous rocks that now occur locally (but may have been widespread) along the Cordilleran margin. Recognition of a continental margin assemblage of possible North American affinity in the Coast Mountains raises the possibility that some arc-type and oceanic terranes inboard of the Coast Mountains may be large klippen that have been thrust over the North American margin.

Cool climate bauxite

The Paleoproterozoic Wernecke Supergroup of Yukon was deposited when the northwestern margin of Laurentia was undergoing major adjustments related to the assembly of the supercontinent Columbia (Nuna) from 1.75 to 1.60 Ga. U–Pb detrital zircon geochronology coupled with Nd isotope geochemistry and major and trace element geochemistry are used to characterize the evolution of the Wernecke basin. The maximum depositional age of the Wernecke Supergroup is reevaluated and is estimated at 1649 ± 14 Ma. Detrital zircon age spectra show a bimodal age distribution that reflects derivation from cratonic Laurentia, with a prominent peak at 1900 Ma. Going upsection, the late Paleoproterozoic peak shifts from 1900 Ma to 1850–1800 Ma, and the proportion of Archean and early Paleoproterozoic zircon decreases. These modifications are a consequence of a change in the drainage system in western Laurentia caused by early phase of the Forward orogeny, several hundred km to the east. The exposed lower and middle parts of the Wernecke Supergroup are correlated with the Hornby Bay Group. Zircon younger than 1.75 Ga appear throughout the sedimentary succession and may have originated from small igneous suites in northern Laurentia, larger source regions such as magmatic arc terranes of the Yavapai and early Mazatzal orogenies in southern Laurentia, and possible arc complexes such as Bonnetia that may have flanked the eastern margin of East Australia. Basins with similar age and character include the Tarcoola Formation (Gawler Craton) and the Willyama Supergroup (Curnamona Province) of South Australia, the Isan Supergroup of North Australia, and the Dongchuan–Dahongshan–Hondo successions of southeast Yangtze Craton (South China). Nd isotope ratios of the Wernecke Supergroup are comparable with values from Proterozoic Laurentia, the Isan and Curnamona assemblages of east Australia, the Gawler Craton, and the Dahongshan–Dongchuan–Hondo successions of the Yangtze Craton of South China. These similarities are compelling evidence for a shared depositional system among these successions. Western Columbia in the Late Paleoproterozoic may have had a dynamic SWEAT-like configuration involving Australia, East Antarctica and South China moving along western Laurentia.