Tectonostratigraphic architecture and uplift history of the Eastern ...

Kurnalpi TerraneThe Kurnalpi Terrane is the central terrane of the Eastern Yilgarn, and is bound to the east by theBurtville Terrane and to the west by the Kalgoorlie Terrane. The bounding faults are the Hootanuiand Ockerburry Fault Systems respectively. Other major faults include the Celia, Mertondale,Keith–Kilkenny, and Emu Faults.The structural synthesis is based on detailed studies of eighteen mines (Winditch, Phoenix,Gladiator South, Telegraph, Lancefield, Jupiter, Transvaal, Westralia, Porphyry, Mt Nambi, MtRedcliff, Mertondale, Celtic, Linger and Die, Puzzle, Butterfly, Dragon, and Parmelia) and eightgranite sites (Murphy, Bernie Bore, Yarrie, Outcamp Bore, Pindinnis, Bulla Rocks, Rainbow, andMullenberry). Most of these granites are internal granites, and intrude older greenstone sequences,and have thus been emplaced into higher structural levels than the external granites. The linkagebetween the structural stages of the internal and external granites provides valuable constraints onthe distribution of strain through the crust. The internal granites also acted as buttresses, and arethemselves commonly only weakly deformed. The Porphyry deposit is both a mine and a granitesite, and Yarrie was a small gold digging within a granite site.Mine and granite sites were selected on the quality of outcrop (although this was sometimes lessthan brilliant) and at a range in structural level and position with respect to major shear zones andregional folds. The 01AGSNY1 regional seismic reflection line from the pmd*CRC transects theentire terrane, and provides additional geometrical constraints on the architecture of the major faultsystems.A self consistent pattern of events/stages and their timing has been defined fro the KurnalpiTerrane. The Kurnalpi Terrane (in this study area) is dominated by the Mt Margaret Anticline (Fig.9), a S–plunging upright fold cored by a multiphase batholith and with sheared limbs to the east bythe Hootanui Shear Zone (Laverton tectonic zone), and to the west by the Celia Shear Zone(tectonic zone). Beardsmore (1999) described the kinematics of the east limb as dextral and the westlimb as sinistral. This study confirms these observations, but suggests that they occurred at differentstages (see below in this section). The western margin of the terrane is marked by the OckerburryFault System, a major E-dipping extensional fault.The Kurnalpi Terrane was deformed by a series of what appears to be long–lived extensional stagesassociated with granite emplacement, interspersed with short–lived contractional stages. As was thecase for the Burtville Terrane, the classical ‘D1’ N–S contractional event of Swager (1997) appearsabsent in the Kurnalpi Terrane. Others have inferred its existence (e.g., Ojala, 1995; Liu and Chen,1998; Beardsmore, 1999). However, Beardsmore (1999) suggested also suggested that the earliestfolds and foliations around the Mt Margaret Anticline could have been extensional in origin, andbeen later folded during the development of the regional anticline.23