Formation and emplacement of the Northland ophiolite, northern New Zealand: SW Pacific tectonic implications

Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between c. 29 and 26 Ma, at c. 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW-SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust-mantle section led to the initiation of are volcanism that resulted in the Northland Lower Miocene volcanic-plutonic suite.published_or_final_versio

Genetic determinants of risk in pulmonary arterial hypertension: international genome-wide association studies and meta-analysis

Background Rare genetic variants cause pulmonary arterial hypertension, but the contribution of common genetic variation to disease risk and natural history is poorly characterised. We tested for genome-wide association for pulmonary arterial hypertension in large international cohorts and assessed the contribution of associated regions to outcomes. Methods We did two separate genome-wide association studies (GWAS) and a meta-analysis of pulmonary arterial hypertension. These GWAS used data from four international case-control studies across 11744 individuals with European ancestry (including 2085 patients). One GWAS used genotypes from 5895 whole-genome sequences and the other GWAS used genotyping array data from an additional 5849 individuals. Cross-validation of loci reaching genome-wide significance was sought by meta-analysis. Conditional analysis corrected for the most significant variants at each locus was used to resolve signals for multiple associations. We functionally annotated associated variants and tested associations with duration of survival. All-cause mortality was the primary endpoint in survival analyses. Findings A locus near SOX17 (rs10103692, odds ratio 1·80 [95% CI 1·55–2·08], p=5·13×10– ¹⁵) and a second locus in HLA-DPA1 and HLA-DPB1 (collectively referred to as HLA-DPA1/DPB1 here; rs2856830, 1·56 [1·42–1·71], p=7·65×10– ²⁰) within the class II MHC region were associated with pulmonary arterial hypertension. The SOX17 locus had two independent signals associated with pulmonary arterial hypertension (rs13266183, 1·36 [1·25–1·48], p=1·69×10– ¹²; and rs10103692). Functional and epigenomic data indicate that the risk variants near SOX17 alter gene regulation via an enhancer active in endothelial cells. Pulmonary arterial hypertension risk variants determined haplotype-specific enhancer activity, and CRISPR-mediated inhibition of the enhancer reduced SOX17 expression. The HLA-DPA1/DPB1 rs2856830 genotype was strongly associated with survival. Median survival from diagnosis in patients with pulmonary arterial hypertension with the C/C homozygous genotype was double (13·50 years [95% CI 12·07 to >13·50]) that of those with the T/T genotype (6·97 years [6·02–8·05]), despite similar baseline disease severity. Interpretation This is the first study to report that common genetic variation at loci in an enhancer near SOX17 and in HLA-DPA1/DPB1 is associated with pulmonary arterial hypertension. Impairment of SOX17 function might be more common in pulmonary arterial hypertension than suggested by rare mutations in SOX17. Further studies are needed to confirm the association between HLA typing or rs2856830 genotyping and survival, and to determine whether HLA typing or rs2856830 genotyping improves risk stratification in clinical practice or trials. Funding UK NIHR, BHF, UK MRC, Dinosaur Trust, NIH/NHLBI, ERS, EMBO, Wellcome Trust, EU, AHA, ACClinPharm, Netherlands CVRI, Dutch Heart Foundation, Dutch Federation of UMC, Netherlands OHRD and RNAS, German DFG, German BMBF, APH Paris, INSERM, Université Paris-Sud, and French ANR

The geochemistry of tholeiitic and alkalic plutonic suites within the Northland ophiolite, northern New Zealand; magmatism in a back arc basin

The Northland ophiolite of New Zealand consists mainly of tholeiitic basalts with subordinate alkalic volcanic rocks. The alkalic rocks occur together with, but are generally younger than the tholeiites. Both the tholeiitic and alkalic suites include minor plutonic intrusives which range from gabbro to plagiogranite. Variations within the tholeiitic plutonic suite can be modelled in terms of low pressure crystal fractionation. The evolution of the alkalic suite is more problematic, because each massif appears to be derived from a slightly different parental magma. New trace element chemistry presented in this study shows that the tholeiitic rocks formed from a mantle source that was compositionally modified by supra-subduction zone processes but that the alkalic suite has a different chemical signature. Nevertheless both suites of rocks are interpreted as having formed in a back arc spreading system. In this environment, the addition of fertile mantle to the supra-subduction wedge, facilitated by subduction roll-back, provided a source for the alkalic rocks with mixed geochemical characteristics. © 1997 Elsevier Science B.V.link_to_subscribed_fulltex