Low-δ18O rhyolites from the Malani Igneous Suite : a positive test for South China and NW India linkage in Rodinia

This study was supported by the National Natural Science Foundation of China (NSFC41572170), “Thousand Youth Talents Plan” grant to Wei Wang, Guangzhou municipal government (201607020029), and MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources (MSFGPMR11 and 01-1). P.A.C. acknowledges support from Australian Research Council grant FL160100168.The Malani Igneous Suite (MIS) in NW India represents one of the best preserved silicic large igneous provinces. Voluminous silicic lavas of the MIS erupted between ca. 780-750 Ma. Zircon grains from rhyolite and dacite lavas have oxygen isotopic compositions that include depleted (δ18O = 4.12 to -1.11‰) and enriched (δ18O = 8.23-5.12‰) signatures. The low-δ18O zircon grains have highly radiogenic Hf isotopic compositions (ƐHf(t)= +13.0 to +3.6), suggesting high temperature bulk cannibalization of upper level juvenile mafic crust as an essential mechanism to produce the low-δ18O felsic magma. Xenocrystic zircon grains in dacites have high δ18O and low ƐHf(t) values for magmas older than 800 Ma, reflecting a dramatic transition in tectono-thermal regime in NW India during 800-780 Ma. A synchronous transition also occurred in South China and Madagascar, suggesting a spatially linked geodynamic system. NW India and South China together with Madagascar and the Seychelles lay either along the periphery of Rodinia or outboards of the supercontinent with the age of convergent plate margin magmatism coinciding with breakup of the supercontinent.Publisher PDFPeer reviewe

How to reduce household costs for people with tuberculosis : a longitudinal costing survey in Nepal

The aim of this study was to compare costs and socio-economic impact of tuberculosis (TB) for patients diagnosed through active (ACF) and passive case finding (PCF) in Nepal. A longitudinal costing survey was conducted in four districts of Nepal from April 2018 to October 2019. Costs were collected using the WHO TB Patient Costs Survey at three time points: intensive phase of treatment, continuation phase of treatment and at treatment completion. Direct and indirect costs and socio-economic impact (poverty headcount, employment status and coping strategies) were evaluated throughout the treatment. Prevalence of catastrophic costs was estimated using the WHO threshold. Logistic regression and generalized estimating equation were used to evaluate risk of incurring high costs, catastrophic costs and socio-economic impact of TB over time. A total of 111 ACF and 110 PCF patients were included. ACF patients were more likely to have no education (75% vs 57%, P = 0.006) and informal employment (42% vs 24%, P = 0.005) Compared with the PCF group, ACF patients incurred lower costs during the pretreatment period (mean total cost: US$55 vs US$87, P < 0.001) and during the pretreatment plus treatment periods (mean total direct costs: US$72 vs US$101, P < 0.001). Socio-economic impact was severe for both groups throughout the whole treatment, with 32% of households incurring catastrophic costs. Catastrophic costs were associated with ‘no education’ status [odds ratio = 2.53(95% confidence interval = 1.16–5.50)]. There is a severe and sustained socio-economic impact of TB on affected households in Nepal. The community-based ACF approach mitigated costs and reached the most vulnerable patients. Alongside ACF, social protection policies must be extended to achieve the zero catastrophic costs milestone of the End TB strategy

Neoproterozoic tectonothermal evolution of NW India: Evidence from geochemistry and geochronology of granitoids

Neoproterozoic granitoids from the Delhi Fold Belt in NW India record formation and evolution of the marginal orogen in the Rodinia supercontinent. The ca. 976 Ma Moras I-type granites show variable SiO2 (67.15-75.87 wt %) and CaO (1.10-324 wt%) and low REE (59-196 ppm). Their spider diagram is characterized by enrichment of Rb, Th and U and depletion of Na and Ta with positive Pb and negative Sr and Ti anomalies. They have positive epsilon(Nd(t)) (+0.41 to +1.40) and epsilon(Hf) (+2.34 to +935) and moderate delta O-18 values (6.48%. to 7.58%.). These features suggest that the Moras granites were produced by melting of the juvenile mafic curst. However, the ca. 811 Ma Pali and ca. 780 Ma Mirpur A-type granites have high SiO2 (74.42-78.63 wt%), K2O + Na2O (7.74-8.95 wt%) and REE (266-334 ppm). Their spider diagrams are more enriched in Rb, Th and U and depleted in Ba, Sr and Ti. They have lower epsilon(Nd) ( - 2.28 to +0.84) and epsilon(Hf) values (-231 to +8.62) than, but similar delta O-18 (5.77%. to 7.01 parts per thousand) to those of the Moras granites, suggesting that the A-type granites were partial melts of the dehydrated mafic crust in a rift setting. The I- and A-type granites in NW India resulted from physicochemical variations of the lithosphere during evolution of the Rodinia. The Neoproterozoic igneous and sedimentary rocks from the Delhi Fold Belt are well correlated with those from the Jiangnan Fold Belt in South China, suggesting that the two belts probably collected together in the configuration of the Rodinia supercontinent. (C) 2018 Elsevier B.V. All rights reserved

Paleomagnetism and geochronology of Malani Igneous Suite, northwest India: implications for the configuration of Rodinia and the assembly of Gondwana

a b s t r a c t New paleomagnetic and geochronologic data from the Malani Igneous Suite (MIS) in Rajasthan, northwest India, improve the paleogeographic reconstruction of the Indian subcontinent between dispersal of the Mesoproterozoic supercontinent Rodinia and late Neoproterozoic assembly of Gondwana. The MIS comprises voluminous phases of felsic and volumetrically insignificant mafic volcanism followed by granitic plutonism. Large (up to 5 m wide) felsic and mafic dikes represent the terminal phase of magmatism. A zircon U-Pb age on a rhyolitic tuff constrains the initial volcanism in the MIS to 771 ± 5 Ma. A paleomagnetic direction obtained from four mafic dikes has a declination = 358.8 • and inclination = 63.5 • (with Ä = 91.2 and ␣ 95 = 9.7). It overlaps with previously reported results from felsic MIS rocks. This direction includes a fine-grained mafic dikelet that showed a reversed direction with declination = 195.3 • and inclination = −59.7 • (Ä = 234.8 and ␣ 95 = 8.1 • ) and also records an overprint of normal polarity from the larger dikes. The VGP obtained from this study on mafic dikes is combined with previous studies of the Malani suite to obtain a mean paleomagnetic pole of 67.8 • N, 72.5 • E (A95 = 8.8 • ). Supported by a tentative baked contact test, we argue that this pole is primary, and permits improved reconstruction of the Indian subcontinent for 771-750 Ma. Data from the MIS and equivalent data from the Seychelles at 750 ± 3 Ma are compared with paleomagnetic data from the 755 ± 3 Ma Mundine Well dikes in Australia to indicate a latitudinal separation of nearly 25 • between the Indian and Australian plates. These suggest that East Gondwana was not amalgamated at ca. 750 Ma and therefore these two cratonic blocks were assembled later into the Gondwana supercontinent, during the ca. 550 Ma Kuunga Orogeny

Slab break-off triggered lithosphere - asthenosphere interaction at a convergent margin: The Neoproterozoic bimodal magmatism in NW India

The Neoproterozoic Malani Igneous Suite (MIS) is described as the largest felsic igneous province in India. The linearly distributed Sindreth and Punagarh basins located along eastern margin of this province represent the only site of bimodal volcanism and associated clastic sediments within the MIS. The in-situ zircon U-Pb dating by LA-ICPMS reveals that the Sindreth rhyolites were erupted at 769-762 Ma. Basaltic rocks from both the basins show distinct geochemical signatures that suggest an E-MORB source for Punagarh basalts (low Ti/V ratios of 40.9-28.2) and an OIB source (high Ti/V ratios of 285-47.6) for Sindreth basalts. In the absence of any evidence of notable crustal contamination, these features indicate heterogeneous mantle sources for them. The low (La/Yb)(CN) (9.34-2.10) and Sm/Yb (2.88-1.08) ratios of Punagarh basalts suggest a spinel facies, relatively shallow level mantle source as compared to a deeper source for Sindreth basalts, as suggested by high (La/Yb)(CN) (7.24-5.24) and Sm/Yb (2.79-2.13) ratios. Decompression melting of an upwelling sub-slab asthenosphere through slab window seems to be the most plausible mechanism to explain the geochemical characteristics. Besides, the associated felsic volcanics show A(2)-type granite signatures, such as high Y/Nb (5.97-1.55) and Yb/Ta (9.36-2.57) ratios, consistent with magma derived from continental crust that has been through a cycle of continent-continent collision or an island-arc setting. A localized extension within an overall convergent scenario is interpreted for Sindreth and Punagarh volcanics. This general convergent setting is consistent with the previously proposed Andean-type continental margin for NW Indian block, the Seychelles and Madagascar, all of which lay either at the periphery of Rodinia supercontinent or slightly off the Supercontinent. (C) 2017 Elsevier B.V. All rights reserved

COUPLED PRECAMBRIAN CRUSTAL EVOLUTION AND SUPERCONTINENT CYCLES. INSIGHTS FROM IN-SITU U-Pb, O- AND Hf-ISOTOPES IN DETRITAL ZIRCON, NW INDIA

Oxygen and hafnium isotopic compositions, measured in-situ on U-Pb dated zircon grains from Paleoproterozoic to early Cambrian successions in NW India have implication for regional crustal evolution and supercontinent cycles. Analyzed zircon grains have high Th/U ratios (>0.1), display strongly fractionated REE patterns, metamorphic overprint, and evidence of interaction with low temperature fluids. Their positive Ce and negative Eu anomalies preclude any Pb loss after zircon crystallization. The U-Pb age spectra (concordance between 90 and 110%) indicate prominent peaks at 2.6 to 2.4 Ga, 1.9 to 1.7 Ga, 1.6 to 1.5 Ga, 1.2 to 1.0 Ga and 0.9 to 0.7 Ga that coincide with the assembly and breakup of Precambrian supercontinents. The Hf model ages of zircon grains with mantle like delta O-18 values reveal continuous generation of the continental crust from 3.3 to 1.3 Ga in NW India with major episodes during 3.3 to 2.7 Ga and 1.7 to 1.5 Ga. These ages correspond well with the 3.4 to 2.9 Ga and 2.2 to 1.6 Ga age peaks recognized in detrital zircon populations from eastern Australia and North America, underlining the significance of these time brackets in continental crust generation during the global continental evolution. Magmatic episodes at 1.9 to 1.7, 1.2 to 1.0 and 0.9 to 0.7 Ga are considered to represent crustal reworking rather than juvenile addition and the former two phases correspond with periods of supercontinent assembly. However, a progressive depletion in O-18 from supra-mantle to mantle values in the 1.7 to 1.5 Ga zircons, coupled with their mantle-like epsilon(Hf(t)) values, indicate at least some juvenile input. Moreover, the 1344 to 1120 Ma zircon grains with low delta O-18(3.7-1.5%o) but high epsilon(Hf(t)) (+8.1- +1.9 with one exception of -2.5) values signify rapid reworking of mantle derived materials in an extensional setting during this period. The 0.9 to 0.7 Ga peak, corresponding to the fragmentation of Rodinia supercontinent, documents crustal reworking that is in contradiction to the generally considered juvenile crustal addition in extensional setting associated with supercontinent breakup

Low-δ¹⁸O rhyolites from the Malani Igneous Suite:a positive test for South China and NW India linkage in Rodinia

The Malani Igneous Suite (MIS) in NW India represents one of the best preserved silicic large igneous provinces. Voluminous silicic lavas of the MIS erupted between ca. 780-750 Ma. Zircon grains from rhyolite and dacite lavas have oxygen isotopic compositions that include depleted (δ18O = 4.12 to -1.11‰) and enriched (δ18O = 8.23-5.12‰) signatures. The low-δ18O zircon grains have highly radiogenic Hf isotopic compositions (ƐHf(t)= +13.0 to +3.6), suggesting high temperature bulk cannibalization of upper level juvenile mafic crust as an essential mechanism to produce the low-δ18O felsic magma. Xenocrystic zircon grains in dacites have high δ18O and low ƐHf(t) values for magmas older than 800 Ma, reflecting a dramatic transition in tectono-thermal regime in NW India during 800-780 Ma. A synchronous transition also occurred in South China and Madagascar, suggesting a spatially linked geodynamic system. NW India and South China together with Madagascar and the Seychelles lay either along the periphery of Rodinia or outboards of the supercontinent with the age of convergent plate margin magmatism coinciding with breakup of the supercontinent