Port Macquarie Research Articles

Preserving geological heritage: addressing destructive sampling and ethical considerations along the unique Port Macquarie Coastal Tract, mid North Coast of NSW, Australia

Preserving geological heritage: addressing destructive sampling and ethical considerations along the unique Port Macquarie Coastal Tract, mid North Coast of NSW, Australia

An inpatient mental health placement for paramedic undergraduate students: a pilot study

BackgroundThe prevalence of mental and behavioural illnesses in the Australian community is increasing. Paramedics are frequently the first health responders to a mental health crisis, and their workload associated with mental health presentations is also increasing. The present study explored the experience and perspectives of undergraduate paramedic students who participated in a pilot mental health placement.MethodsA pilot workplace learning opportunity was established in which students completed a portion of their community service hours in an inpatient mental health setting at Port Macquarie Base Hospital. Eight students attended and completed the placement and were administered the Clinical Placement Evaluation Questionnaire.ResultsStudent responses to this placement experience were overwhelmingly positive. The data showed that all the students responded “Strongly Agree” or “Agree” to each of the survey items. Thematic analysis of the qualitative data yielded four central themes related to benefits, additional training and education, nursing staff, and improvements.ConclusionsThis pilot study suggests that mental health placements for paramedics have meaningful educational value and can impact student learning. Since this pilot study, mental health placements have been permanently included as part of the undergraduate curriculum in our institution.

Haematoma block is the most efficient technique for closed forearm fracture reduction: a retrospective cohort study

BackgroundForearm fractures are a common ED presentation. This study aimed to compare the resource utilisation of three anaesthetic techniques used for closed forearm fracture reduction in the ED: haematoma block...

Rheology modification in a subduction channel due to eclogite facies metasomatism (Rocky Beach Metamorphic Mélange, Port Macquarie, Australia)

The rheological properties of the interface between the down-going and overriding plates in subduction zones provides insight into how plate convergence is accommodated and the controls on seismic and aseismic slip. This interface is known as the subduction channel and exhumed examples provide the only direct information on deformation mechanisms and the impact of metamorphism on rheology. The Rocky Beach Metamorphic Mélange in eastern Australia is one such exhumed subduction channel, composed of eclogite, blueschist and greenschist facies blocks within a mélange matrix. Previous phase equilibria modelling indicates that high pressure blocks were subducted to ca. 100 km depth and then retrogressed during return flow and exhumation. We found that the rheology of blocks is modified by metasomatism, consistent with studies on other subduction channels. However, through comparison of blocks from different metamorphic grades we found that the effect of metasomatism on rheology varied depending on the pressure and temperature conditions of metasomatism. While unmetasomatised eclogites behaved as rigid objects in the mélange matrix, rocks with mineral assemblages that equilibrated during eclogite facies metasomatism accumulated significant strain, forming isoclinal folds and refolded folds. Deformation of these blocks began at eclogite facies and continued during return flow and retrogression to blueschist facies. At blueschist facies, metasomatised blocks developed mm-scale isoclinal folds with shearing parallel to fold limbs forming rootless isoclinal folds. At the transition between blueschist and greenschist facies, pressure solution became important, preferentially focusing along layers of lawsonite, dissolving it from the rock. At greenschist facies, dissolution-precipitation processes caused significant mass loss, producing mm-spacing between pressure solution seams and cuspate folds, analogous to dewatering structures in sediments. In the Rocky Beach Metamorphic Mélange eclogite facies metasomatism reduces the competence of rigid blocks, reducing overall subduction channel heterogeneity during return flow. We suggest that subduction channels that experience widespread eclogite facies metasomatism may be less likely to generate seismic slip during return flow, since the proportion of rigid blocks and block strength are both reduced.

Serrated polyposis syndrome: defining the epidemiology and predicting the risk of dysplasia.

Serrated polyposis syndrome is the most common polyposis syndrome that has neoplastic potential. However, the natural history, genetic basis, and risk of dysplasia and neoplasia of serrated polyposis syndrome are incompletely understood. The objective of this study is to define the epidemiology of serrated polyposis syndrome. Using this data, we aim to evaluate candidate variables for predicting the risk of dysplasia and neoplasia in sessile serrated lesions found in serrated polyposis syndrome patients. Finally, we aim to use this data to create and evaluate clinical prediction models for accuracy in predicting dysplastic sessile serrated lesions in serrated polyposis syndrome patients. This was a regional Australian single-centre retrospective cohort study. Data was prospectively collected data from the clinical record database of a regional Australian gastroenterology practice. All patients undergoing colonoscopy at Port Macquarie Gastroenterology between January 2015 and September 2021 were screened for this study. Collected data included patient demographic, endoscopic, and histopathological findings. Clinical and endoscopic multivariate logistic regression models were created to predict dysplastic sessile serrated lesions. Model performance was examined using the area under the receiver operating curve. In total 8401 patients underwent a colonoscopy procedure during the study period. Serrated polyposis syndrome was diagnosed in 247, representing a prevalence of 2.94% (mean age 67.15 years, 62.75% female). Logistic regression identified; older age at serrated polyposis syndrome diagnosis, a personal history of colorectal cancer, size of the largest sessile serrated lesions removed, and total sessile serrated lesions count as predictors of dysplastic sessile serrated lesions. The clinical and endoscopic model had an area under the receiver operating curve of 0.75. Serrated polyposis syndrome is more common than previously described. The clinical and endoscopic variables identified in logistic regression have acceptable accuracy in predicting the risk of dysplasia, however other populations need to be studied to achieve generalisability and improve model performance.

Koala admissions to a wildlife hospital in coastal New South Wales, Australia, over a nine-year period, 2014–2022

The koala (Phascolarctos cinereus) population in Australia has been subjected to numerous threats leading to a significant decline in their numbers. The Port Macquarie region serves as a vital habitat for these iconic marsupials. Analysing records of 1227 koalas admitted to the Port Macquarie Koala Hospital (2014–2022), this study aimed to understand admission causes, temporal trends, and risk factors. Anthropogenic activities accounted for almost half (49.7%) of all admissions with ‘dangerous area’ and ‘motor vehicle accident’ (MVA) being common aetiologies. Young koalas were more susceptible to ‘dangerous area’, ‘MVA’, and ‘dog attack’ than other age groups. Koalas admitted for suspected chlamydia were also a significant contributing factor for admissions, and was most common in young koalas. Overall, the majority of koalas were candidates for rehabilitation or release (54.3%), but mature and aged koalas had the highest odds for mortality. This study highlights the ongoing impact of anthropogenic activities on koalas, emphasises the need for public education and reporting to mitigate risks, and underscores the importance of addressing diseases like chlamydia. These results contribute to our understanding of the factors influencing koala hospital admissions and can inform conservation and management strategies for this iconic Australian species.

The Port Macquarie Settlement, New South Wales, 1821–1847: Interconnections within Landscapes of Convict Labor and Industry

This article explores the convict-punishment settlement of Port Macquarie on the mid-north coast of New South Wales between 1821 and 1847. Synthesizing previous and new historical and archaeological research, it identifies a range of major and minor sites of labor, accommodation, reform, and punishment within the settlement’s landscape during its period as a restricted convict prison from 1821 to 1830. From this it reconstructs the network of labor provision and infrastructure development, which we argue was not just about making the settlement economically self-sustaining, but also intended to create the framework for a transition to a “free” settlement. To this end this article also examines the ways in which that transformation occurred, with former sites of convict labor and the convicts themselves transitioning from government control to private settlers, until the withdrawal of the government infrastructure for convict management in 1847.

Climate Change Effects on the Predicted Heat Strain and Labour Capacity of Outdoor Workers in Australia.

Global heating is subjecting more of the planet to longer periods of higher heat stress categories commonly employed to determine safe work durations. This study compared predicted worker heat strain and labour capacity for a recent normal climate (1986-2005) and under commonly applied climate scenarios for the 2041-2080 period for selected Australian locations. Recently published heat indices for northern (Darwin, Townsville, and Tom Price) and south-eastern coastal and inland Australia locations (Griffith, Port Macquarie, and Clare) under four projected climate scenarios, comprising two representative concentration pathways (RCPs), RCP4.5 and RCP8.5, and two time periods, 2041-2060 and 2061-2080, were used. Safe work durations, before the threshold for core temperature (38.0 °C) or sweat loss (5% body mass) are attained, were then estimated for each scenario using the predicted heat strain model (ISO7933). The modelled time to threshold core temperature varied with location, climate scenario, and metabolic rate. Relative to the baseline (1986-2005), safe work durations (labour capacity) were reduced by >50% in Port Macquarie and Griffith and by 20-50% in northern Australia. Reaching the sweat loss limit restricted safe work durations in Clare and Griffith. Projected future climatic conditions will adversely impact the predicted heat strain and labour capacity of outdoor workers in Australia. Risk management strategies must adapt to warming conditions to protect outdoor workers from the deleterious effects of heat.

Precambrian history of the Pacific Mantle Domain: New constraints from Woodsreef and Port Macquarie serpentinized spinel harzburgites of the New England Orogen, Australia

Abstract The present-day mantle is divided into the African and Pacific domains by the circum-Pacific subduction girdle. Very little is known about the mantle composition of the Pacific Domain before 120 Ma due to the scarcity of the oceanic record, having mostly been destroyed by subduction processes. Accreted oceanic lithosphere (ophiolites) in orogens along the Paleo-Pacific margins provide rare opportunities to partially fill this knowledge gap. The early Cambrian (530–505 Ma) Weraerai ophiolite mélange in the New England Orogen in Eastern Australia represents fragments of the now-consumed Paleo-Pacific oceanic plate, predecessor of the Panthalassa and Pacific oceanic plates, accreted to east Gondwana during ca. 410–277 Ma. Early work revealed the presence of an accreted volcanic island(s) of possible mantle plume origin. However, due to their heavy alteration and weathering, the geochemical signature of the mafic rocks in the Weraerai ophiolite cannot be used to certify their plume origin with confidence. Therefore, mantle rocks found in the ophiolitic belt offer an alternative way to decipher the origin of the oceanic lithospheric fragments in the Weraerai ophiolite mélange. Here we report the petrographic, major, and trace elements composition, including highly siderophile elements (HSE), and Re-Os isotope composition for 16 serpentinized spinel harzburgite samples from Woodsreef and Port Macquarie. The observed spinel-orthopyroxene symplectite intergrowth textures are interpreted as garnet-breakdown textures due to cooling from an initial high temperature of >1200°C. Silicon and Al contents and Mg# of serpentinized spinel harzburgite, as well as heavy rare earth element modelling results, suggest a high-degree of melt extraction of 20–30% in the garnet stability field and in an anhydrous environment, probably in ocean island or oceanic plateau environments. The samples in this study have HSE concentrations interpreted to have resulted from post-melting processes rather than a melt extraction feature, indicating that their Re-Os model ages need to be interpreted with caution. Nevertheless, the melt depletion ages obtained from the Woodsreef and Port Macquaries samples range between 1.4 and 1.1 Ga, consistent with previous studies on other Pacific-rim ophiolitic rocks. We argue that these ages might be related to a major depletion event during the transition between supercontinents Nuna and Rodinia. Such depletion events affected a large proportion of this section of the mantle before the incorporation of the peridotites into the oceanic lithosphere in the Paleo-Pacific associated with rapid ascent of mantle plumes. This interpretation is consistent with the occurrence of accreted volcanic islands in the Werearai ophiolite mélange, as shown by the OIB chemical signatures of some of the mafic rocks, and their association with shallow water limestones that formed in near-equatorial latitudes. The proposed ca. 530–510 Ma Paleo-Pacific Ocean mantle plume event coincides with a global peak of oceanic mantle plume events that may record the legacy of a circum-Rodinia subduction girdle driving antipodal mantle superplume episodes.

Informing the Future of Integrated Digital and Clinical Mental Health Care: Synthesis of the Outcomes From Project Synergy.

BackgroundGlobally, there are fundamental shortcomings in mental health care systems, including restricted access, siloed services, interventions that are poorly matched to service users’ needs, underuse of personal outcome monitoring to track progress, exclusion of family and carers, and suboptimal experiences of care. Health information technologies (HITs) hold great potential to improve these aspects that underpin the enhanced quality of mental health care.ObjectiveProject Synergy aimed to co-design, implement, and evaluate novel HITs, as exemplified by the InnoWell Platform, to work with standard health care organizations. The goals were to deliver improved outcomes for specific populations under focus and support organizations to enact significant system-level reforms.MethodsParticipating health care organizations included the following: Open Arms–Veterans & Families Counselling (in Sydney and Lismore, New South Wales [NSW]); NSW North Coast headspace centers for youth (Port Macquarie, Coffs Harbour, Grafton, Lismore, and Tweed Heads); the Butterfly Foundation’s National Helpline for eating disorders; Kildare Road Medical Centre for enhanced primary care; and Connect to Wellbeing North Coast NSW (administered by Neami National), for population-based intake and assessment. Service users, families and carers, health professionals, and administrators of services across Australia were actively engaged in the configuration of the InnoWell Platform to meet service needs, identify barriers to and facilitators of quality mental health care, and highlight potentially the best points in the service pathway to integrate the InnoWell Platform. The locally configured InnoWell Platform was then implemented within the respective services. A mixed methods approach, including surveys, semistructured interviews, and workshops, was used to evaluate the impact of the InnoWell Platform. A participatory systems modeling approach involving co-design with local stakeholders was also undertaken to simulate the likely impact of the platform in combination with other services being considered for implementation within the North Coast Primary Health Network to explore resulting impacts on mental health outcomes, including suicide prevention.ResultsDespite overwhelming support for integrating digital health solutions into mental health service settings and promising impacts of the platform simulated under idealized implementation conditions, our results emphasized that successful implementation is dependent on health professional and service readiness for change, leadership at the local service level, the appropriateness and responsiveness of the technology for the target end users, and, critically, funding models being available to support implementation. The key places of interoperability of digital solutions and a willingness to use technology to coordinate health care system use were also highlighted.ConclusionsAlthough the COVID-19 pandemic has resulted in the widespread acceptance of very basic digital health solutions, Project Synergy highlights the critical need to support equity of access to HITs, provide funding for digital infrastructure and digital mental health care, and actively promote the use of technology-enabled, coordinated systems of care.

Supporting actors: reclaiming learning spaces

This keynote was given at the Improving University Teaching International Conference, Charles Sturt University, Port Macquarie, NSW, in 2018. In this presentation I explore the spaces inhabited by teaching-focused academics and how this supports or hinders their development. The keynote is based on the work I did for my PhD, which can be found in the British Library EThOS repository and University of Durham e-theses repository.

Can Public Spaces Effectively Be Used as Cleaner Indoor Air Shelters during Extreme Smoke Events?

During extreme air pollution events, such as bushfires, public health agencies often recommend that vulnerable individuals visit a nearby public building with central air conditioning to reduce their exposure to smoke. However, there is limited evidence that these “cleaner indoor air shelters” reduce exposure or health risks. We quantified the impact of a “cleaner indoor air shelter” in a public library in Port Macquarie, NSW, Australia when concentrations of fine particulate matter (PM2.5) were elevated during a local peat fire and nearby bushfires. Specifically, we evaluated the air quality improvements with central air conditioning only and with the use of portable high efficiency particulate air (HEPA) filter air cleaners. We measured PM2.5 from August 2019 until February 2020 by deploying pairs of low-cost PM2.5 sensors (i) inside the main library, (ii) in a smaller media room inside the library, (iii) outside the library, and (iv) co-located with regulatory monitors located in the town. We operated two HEPA cleaners in the media room from August until October 2019. We quantified the infiltration efficiency of outdoor PM2.5 concentrations, defined as the fraction of the outdoor PM2.5 concentration that penetrates indoors and remains suspended, as well as the additional effect of HEPA cleaners on PM2.5 concentrations. The infiltration efficiency of outdoor PM2.5 into the air-conditioned main library was 30%, meaning that compared to the PM2.5 concentration outdoors, the concentrations of outdoor-generated PM2.5 indoors were reduced by 70%. In the media room, when the HEPA cleaners were operating, PM2.5 concentrations were reduced further with a PM2.5 infiltration efficiency of 17%. A carefully selected air-conditioned public building could be used as a cleaner indoor air shelter during episodes of elevated smoke emissions. Further improvements in indoor air quality within the building can be achieved by operating appropriately sized HEPA cleaners.

Playspace users’ experience of a socially inclusive playspace: the case study of Livvi’s Place, Port Macquarie, New South Wales, Australia

ABSTRACT Inclusive play is a fundamental right for all children however few studies exist on playspaces and children with impairment. Drawing on Australia’s early childhood learning framework, Belonging, Being and Becoming, this study aims to explore whether Livvi’s Place, an inclusive playspace in Port Macquarie, Australia, met the principles and values articulated in the framework, and whether the playspace, was meeting its goal of social inclusion. One hundred and ninety three online and face-to-face questionnaire surveys of adult playspace users were completed. The early childhood learning framework was used to inform the survey design and analytical framework. Results indicate the playspace model adopted promotes a sense of social inclusion as users expressed feelings of safety, welcome, and of belonging at the playspace. Users felt they could be themselves, live in the moment, and enjoy their experiences there. The friendships formed, conversations started, and playful interactions experienced at Livvi’s Place demonstrate that it facilitates people connecting and becoming members of the local community. Findings revealed Livvi’s Place was meeting the principles and values of Belonging, Being and Becoming and meeting its goal of social inclusion. Areas for improvement were identified, providing future learning opportunities for inclusive playspace development and provision.

Source of Detritus in Subducted Turbidites, Tectonic Mélange, Port Macquarie Block, Southern New England Orogen, Australia—A Geochemical Perspective

A tectonic mélange containing blueschists and eclogites, Middle Ordovician mid-ocean ridge basalt, cherts, and clastic sediments occurs at Port Macquarie in the southern New England Orogen, Australia. The clastics are quartz-poor and are dominated by mafic volcanic and fragmented plagioclase clasts; felsic volcanic clasts are less common. They exhibit erosional bases, graded bedding, load structures, and lithologies ranging from laminated mudstones to pebbly sandstones. Based on these features, they are interpreted as turbidites. During subduction, these turbidites were deformed and metamorphosed under prehnite–pumpellyite and lower greenschist facies conditions. Geochemically, they have a calc-alkaline, intra-oceanic arc signature; show no recycling; and have been derived from a provenance dominated by mafic volcanic rocks of basaltic-andesite composition. Further, chemical index of alteration (44–69) and Index of Compositional Variability (0.8–2.4) data reveal they show little weathering and are immature. The lack of weathering of rocks in a location where tropical climatic conditions existed is attributed to extreme erosion associated with a dynamic setting resulting in rapid transportation of the sediments to the fore arc basin and subsequently to the trench. As a consequence, little time was available for weathering to take place. The detritus in the turbidites is thought to have been derived from Late Ordovician volcanics in the Macquarie Arc and fore arc basin sequences of the Murrawong Formation. The cherts with which they are associated record both a continental and oceanic arc geochemical signature.

Management and Outcomes of STEMI in a Regional Non-24/7 Cardiac Catheterisation Lab

Numerous challenges are associated with the management of STEMI in regional Australia due to geographical distance prolonging transfers and lack of 24/7 cardiac services. We investigated the management and outcomes of STEMI patients presenting to Port Macquarie Base Hospital (PMBH) which operates a non-24/7 cath lab service.

A 29-year retrospective analysis of koala rescues in New South Wales, Australia.

The koala (Phascolarctos cinereus) is currently listed by both the IUCN and the Australian Governments’ Threatened Species Scientific Committee as vulnerable to extinction with an overall decreasing population trend. It is unknown exactly how many koalas remain in the wild, but it is known that habitat fragmentation and bushfires have ultimately contributed to the decline of the koala all over Australia. This novel study is a retrospective analysis of data over a 29-year period (1989–2018) using records for 12,543 sightings and clinical care admissions for wild koalas from the major koala hot-spots (Port Stephens, port Macquarie and Lismore) in New South Wales, Australia. This study aims to understand the long-term patterns and trends of key stressors that are contributing to the decline of koalas in New South Wales, and the synergic interactions of factors such as rescue location, sex and age of the koala, and if their decline is influenced progressively by year. The main findings of this retrospective analysis indicated that between all 3 rescue sites, the most common prognosis was disease, the most common disease was signs of chlamydia, and the most common outcome was release. The location where the highest number of koalas were found prior to being reported as sighted or admitted into clinical care was within the regional area of Lismore. Furthermore, sex was not a discriminating factor when it came to prognosis or outcome, but age was significant. Finally, incidents of disease were found to increase over long-term, whereas release decreased over time and euthanasia increased. The wealth of data available to us and the retrospective analysis enabled us in a way to ‘zoom out’ and reveal how the key environmental stressors have fluctuated spatially and temporally. In conclusion, our data provides strong evidence of added pressures of increased human population growth in metropolitan zones, which increases risks of acute environmental trauma and proximate stressors such as vehicle collisions and dog-attacks as well as increased sightings of virtually healthy koalas found in exposed environments. Thus our ‘zoom out’ approach provides support that there is an urgent need to strengthen on-ground management, bushfire control regimes, environmental planning and governmental policy actions that should hopefully reduce the proximate environmental stressors in a step wise approach. This will ensure that in the next decade (beyond 2020), NSW koalas will hopefully start to show reversed trends and patterns in exposure to environmental trauma and disease, and population numbers will return towards recovery and stability.

A retrospective observational study on enterococcal bacteraemia and endocarditis at a regional hospital in New South Wales, Australia.

Enterococcal infection poses a major clinical problem due to increasing antibiotic resistance and rising numbers of health care related infections. It is also associated with high morbidity and mortality. The aim of this study is to examine demographic characteristics, co-morbidities and clinical outcomes of the patients as well as susceptibility spectrum of all Enterococcal bacteraemia and endocarditis. A retrospective observational study was performed on cases of Enterococcal bacteraemia and endocarditis at Port Macquarie Base Hospital, New South Wales, Australia from 1st January 2012 till 31st December 2018. Out of 75 patients with Enterococcal bacteraemia, about 70% were male. E.faecalis was responsible for about two-thirds of bacteraemia. E.faecalis most commonly presented as infective endocarditis whereas intraabdominal infection was the most common presentation for E.faecium. 90-day all-cause mortality for all Enterococcal bacteraemia was 29.3% (22 out of 75) with a higher mortality rate with E.faecium bacteraemia in comparison to E.faecalis bacteraemia (47.8% Vs 20.8%). Vancomycin resistance was noted only in 17.4% of E.faecium species. There were 18 patients with infective endocarditis over 7 years period with a yearly prevalence rate of 2.6%. Readmission was 78% and mortality was 16.7% within 90 days of admission. Regarding the use of echocardiogram, about 41.3% of Enterococcal bacteraemia did not have echocardiograms. Enterococcal bacteraemia was associated with high morbidity and mortality, particularly secondary to E.faecium bacteraemia. Enterococcal IE was associated with high rates of complications, readmissions, and prolonged inpatient stay.

Colonial penal stations and uneven legal reform after the Bigge Commission of Inquiry: the Port Macquarie absconders at Macquarie Harbour

Between 1822 and 1824, just under 100 convict absconders from the mainland penal settlement at Port Macquarie were relocated to Van Diemen’s Land under executive orders they be retained at the island’s new penal station at Macquarie Harbour. The subsequent fate of this cohort reveals an early moment of divergence in policy and practice between the two colonies. Two years later, when the New South Wales government tacitly acknowledged that many convicts had been illegally sentenced to penal stations by magistrates, the benefits of that disclosure were not extended to those mainland convicts who had been relocated south to Van Diemen’s land. Nor, importantly, were they extended to Vandemonian convicts whose sentences were equally suspect. This article considers how developments in New South Wales which served to sharpen thinking about the nature and role of colonial penal settlements passed virtually unnoticed in Van Diemen’s Land, allowing the local authorities to evade much larger questions about magisterial sentencing practices and the application of English criminal transportation law.

Bushfires and burns

Journal of Paramedic PracticeVol. 12, No. 2 EditorialBushfires and burnsPhillip EbbsPhillip EbbsAustralian paramedic and researcherSearch for more papers by this authorPhillip EbbsPublished Online:10 Feb 2020https://doi.org/10.12968/jpar.2020.12.2.51AboutSectionsView articleView Full TextPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareShare onFacebookTwitterLinked InEmail View articleReferencesRubbo L, Wellauer K. Waves of ash wash up on NSW beaches, Port Macquarie records world's dirtiest air as bushfires burn. 2019. https://www.abc.net.au/news/2019-11-15/nsw-bushfires-make-port-macquarie-most-polluted-place/11708612 (accessed 3 February 2020) Google ScholarWales D, Stiles K. Saving lives is not enough. 2019. https://www.ctif.org/sites/default/files/2019-10/Saving%20Lives%20is%20not%20Enough.pdf (accessed 3 February 2020) Google Scholar FiguresReferencesRelatedDetails 2 February 2020Volume 12Issue 2ISSN (print): 1759-1376ISSN (online): 2041-9457 Metrics History Published online 10 February 2020 Published in print 2 February 2020 Information© MA Healthcare LimitedPDF download

Subduction and accumulation of lawsonite eclogite and garnet blueschist in eastern Australia

AbstractLawsonite eclogite and garnet blueschist occur as metre‐scale blocks within serpentinite mélange in the southern New England Orogen (SNEO) in eastern Australia. These high‐P fragments are the products of early Palaeozoic subduction of the palaeo‐Pacific plate beneath East Gondwana. Lu–Hf, Sm–Nd, and U–Pb geochronological data from Port Macquarie show that eclogite mineral assemblages formed between c. 500 and 470 Ma ago and became mixed together within a serpentinite‐filled subduction channel. Age data and P–T modelling indicate lawsonite eclogite formed at ~2.7 GPa and 590°C at c. 490 Ma, whereas peak garnet in blueschist formed at ~2.0 GPa and 550°C at c. 470 Ma. The post‐peak evolution of lawsonite eclogite was associated with the preservation of pristine lawsonite‐bearing assemblages and the formation of glaucophane. By contrast, the garnet blueschist was derived from a precursor garnet–omphacite assemblage. The geochronological data from these different aged high‐P assemblages indicate the high‐P rocks were formed during subduction on the margin of cratonic Australia during the Cambro‐Ordovician. The rocks however now reside in the Devonian–Carboniferous southern SNEO, which forms the youngest and most outboard of the eastern Gondwanan Australian orogenic belts. Geodynamic modelling suggests that over the time‐scales that subduction products accumulated, the high‐P rocks migrated large distances (~>1,000 km) during slab retreat. Consequently, high‐P rocks that are trapped in subduction channels may also migrate large distances prior to exhumation, potentially becoming incorporated into younger orogenic belts whose evolution is not directly related to the formation of the exhumed high‐P rocks.