The Serra do Caparaó Complex, Mantiqueira Province, Brazil, revisited: metamorphic age constraints by U-Pb and Lu-Hf method in zircon by LA-ICP-MS

Southeastern Bulgaria is composed of a variety of rocks from pre-Variscan (ca. 0.3 Ga) to pre-Alpine sensu lato (ca. 0.15 Ga) time. The Sakar Unit in this region comprises a series of granitoids and gneisses formed or metamorphosed during these events. It is cut by a series of post-Variscan hydrothermal veins, yet lacks pervasive Alpine deformation. It thus represents a key unit for detecting potential tectonism associated with the enigmatic Cimmerian Orogenic episode, but limited geochronology has been undertaken on this unit. Here we report age constraints on hydrothermal activity in the Sakar Pluton. The investigated veins contain mainly albite–actinolite–chlorite–apatite–titanite–quartz–tourmaline–epidote and accessory minerals. The most common accessory minerals are rutile and molybdenite. Apatite and titanite from the same vein were dated by U–Pb LA–ICP-MS geochronology. These dates are interpreted as crystallization ages and are 149 ± 7 Ma on apatite and 114 ± 1 Ma on titanite, respectively. These crystallization ages are the first to document two stages of hydrothermal activity during the late Jurassic to early Cretaceous, using U–Pb geochronology, and its association with the Cimmerian orogenesis. The Cimmerian tectono-thermal episode is well-documented further to the east in the Eastern Strandja Massif granitoids. However, these are the first documented ages from the western parts of the Strandja Massif, in the Sakar Unit. These ages also temporally overlap with previously published Ar–Ar and K–Ar cooling ages, and firmly establish that the Cimmerian orogeny in the studied area included both tectonic and hydrothermal activity. Such hydrothermal activity likely accounted for the intense albitization found in the Sakar Unit.

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Geochronologic constraints on the Shuram excursion in Oman

10.5194/egusphere-egu2020-10839 ◽

2020 ◽

Author(s):

Marjorie Cantine ◽

Alan Rooney ◽

Ulf Linneman ◽

Mandy Hofmann ◽

Richard Albert ◽

...

Keyword(s):

Inner Core ◽

Black Shales ◽

Depositional Environments ◽

Driving Mechanism ◽

Global Correlation ◽

Carbon Isotope Excursion ◽

Icp Ms ◽

Absolute Age ◽

Low Magnetic Field ◽

Age Constraints

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; The rise of animals occurred during an interval of Earth history that witnessed highly dynamic atmosphere-ocean redox conditions; regional, transient glaciations; extraordinarily low magnetic field intensities potentially related to inner core formation; and perturbations to the global carbon cycle of a size not seen before or since. The largest of these, the Shuram carbon isotope excursion, has been invoked as a driving mechanism for, or consequence of, various biological and geological events during the Ediacaran Period. However, there are a number of major controversies regarding the Shuram, including its timing. Without age constraints on its onset or duration, it is impossible to confidently connect the Shuram Event with any biological or geological upheavals.Here, we apply multiple methods, including Re-Os on black shales and U-Pb LA-ICP-MS dating on carbonates, to well-preserved Ediacaran stratigraphy from Oman, deriving new age controls in previously undated parts of the stratigraphy. Our new data show that paired Re-Os shale and U-Pb carbonate analyses constrain the onset and duration of the Shuram excursion in Oman. The results&#8212;which are consistent with recent age constraints on Shuram-bearing stratigraphy from Northwest Canada (Rooney et al. 2019, Goldschmidt)&#8212;demonstrate the utility of leveraging multiple geochronological techniques within a single basin to constrain deposition in deep to shallow depositional environments. The results also provide key absolute age constraints on the onset of the Shuram excursion in the stratigraphy where it was first defined, critical for testing global correlation schemes, constructing a temporal framework for the Ediacaran period, and identifying causal mechanisms during this interval of geobiological and geodynamic dynamism.&#160;

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Laser Ablation ICP-MS U-Pb and 40Ar-39Ar age constraints on Neoarchean to Paleoproterozoic magmatic and tectono-metamorphic evolution of the link between Hope Bay and Elu greenstone belts, northeast Slave craton, NWT, Canada

Gondwana Research ◽

10.1016/j.gr.2017.06.012 ◽

2017 ◽

Vol 51 ◽

pp. 1-16 ◽

Cited By ~ 1

Author(s):

H. Mvondo ◽

D. Lentz ◽

M. Bardoux ◽

C.M. McFarlane ◽

D. Archibald

Keyword(s):

Laser Ablation ◽

Metamorphic Evolution ◽

Slave Craton ◽

Icp Ms ◽

Greenstone Belts ◽

Age Constraints ◽

Hope Bay

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LA-ICP-MS U–Pb zircon, columbite-tantalite and40Ar–39Ar muscovite age constraints for the rare-element pegmatite dykes in the Altai orogenic belt, NW China

Geological Magazine ◽

10.1017/s0016756816001096 ◽

2016 ◽

Vol 155 (3) ◽

pp. 707-728 ◽

Cited By ~ 9

Author(s):

QIFENG ZHOU ◽

KEZHANG QIN ◽

DONGMEI TANG ◽

CHUNLONG WANG ◽

PATRICK ASAMOAH SAKYI

Keyword(s):

Late Jurassic ◽

Middle Triassic ◽

Temporal Distribution ◽

Middle Permian ◽

Magmatic Activity ◽

Weighted Mean ◽

Rare Element ◽

Nw China ◽

Icp Ms ◽

Age Constraints

AbstractThe Chinese Altai is renowned for its rich rare-element resources. Nine representative rare-element (REL) pegmatites were dated using LA-ICP-MS and40Ar–39Ar methods. The columbite grains yield a weighted mean206Pb/238U age of 239.6±3.8 Ma for the Dakalasu (Be-Nb-Ta) pegmatite and concordia U–Pb ages of 258.1±3.1 Ma and 262.3±2.5 Ma for the Xiaokalasu (Li-Nb-Ta) pegmatite. The zircons display a weighted mean206Pb/238U age of 198.5±2.5 Ma for the Husite (Be) pegmatite and concordia U–Pb ages of 194.3±1.6 Ma and 248.2±2.2 Ma for the Qunkuer (Be) and Taerlang (barren) pegmatites. The muscovite40Ar–39Ar dating gives plateau ages of 286.4±1.6 Ma, 297.0±2.6 Ma, 265.2±1.5 Ma, 178.8±1.0 Ma, 162.2±0.9 Ma, 237.7±1.3 Ma, 237.4±1.2 Ma and 231.9±1.2 Ma for the Talate (Li-Be-Nb-Ta), Baicheng (Nb-Ta), Kangmunagong (barren), Husite (Be), Qunkuer (Be-Nb-Ta), Xiaokalasu (Li-Nb-Ta), Weizigou (Be) and Taerlang (barren) pegmatites, respectively. These new ages coupled with previous geochronological work suggest that the REL pegmatites in the Chinese Altai formed during early Permain – Late Jurassic time. The REL pegmatites located in the Central Altaishan terrane are younger than those in the Qiongkuer–Abagong terrane, showing a correlation with the coeval and adjacent granites. The formation of the REL pegmatites and these granites indicates frequent and strong magmatic activity in the post-orogenic and anorogenic setting. The spatial and temporal distribution of pegmatites and granites reveals a magmatism path from the SE (of age early–middle Permian), to the NW (middle Permian – Middle Triassic) and finally to the central part (Middle Triassic – Jurassic) of the Chinese Altai.

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