Evidence for large-scale Laramide tectonic inversion and a mid-Tertiary caldera ring fracture zone at the Lightening Dock geothermal system, New Mexico
Stratigraphy in a recent intermediate depth (2100 ft) geothermal test hole is interpreted along side previous deep (7001 to 7404 ft depth) exploration holes to study large-scale structural controls for the Lightning Dock geothermal system and refine the stratigraphic and structural characterization of the shallow reservoir. Laramide compression and large-scale tectonic inversion of a northwest-trending Late Jurassic-Early Cretaceous extensional structure at the Lightning Dock geothermal site represents deformation that may exceed Neogene extensional processes in magnitude and duration and provide potential for a significant volume of shattered rock. Also, volcanic stratigraphy supports the hypothesis of Elston et al. (1983) for a midTertiary caldera ring fracture zone in the vicinity the geothermal area. Northeastand north-trending Neogene normal faults that cross cut older structures provide additional preparation of fractured ground. A north-trending Pleistocene normal fault may reopen older fractures that are favorably oriented and allow concentration and upward flow of deep-seated geothermal fluids. Because the Lightning Dock geothermal system is “blind” and has no surface manifestations, a better understanding of structures buried beneath Neogene alluvial basin fill may have application in geothermal exploration to find similar “blind” geothermal systems elsewhere in southern New Mexico and southeastern Arizona. FIGURE 1. Shaded relief topographic location map of the Lightning Dock geothermal area.
A Review of Exploration Methods for Discovering Hidden Geothermal Systems
One of the tasks of the Exploration team for the US DOE Geothermal Technologies Office Geothermal Vision study is to evaluate the distribution and likely future deployment of geothermal resources for power generation. The 2008 USGS assessment of geothermal resources in the western US noted that the largest potential resource base consists of enhanced geothermal systems (EGS); however, significant technical and economic challenges remain to be overcome before largescale commercial utilization of this resource type can occur. Of the remaining moderate and high temperature resources, undiscovered hydrothermal systems (which are typically hidden systems with no surface thermal manifestations) have three times the resource potential than identified hydrothermal systems. If geothermal field development rates are to increase above the current rate of deployment, the discovery of hidden systems will be a critical need. To assist future exploration of these systems, this study reviews successful discoveries of hidden geothermal systems that have been developed in the Imperial Valley and Basin and Range provinces, and summarizes the different exploration methods that have been utilized in these efforts. Based on this review, several initial recommendations are made that might reduce the risk associated with exploration of hidden systems.
Organic geochemical characteristics and depositional setting of Tertiary organic-rich sediments from onshore Penyu Basin, Malaysia
Due to the poor knowledge of the organic facies characteristics of the eastern Chenor Pahang has made it remain an untapped potential in the Penyu Basin. Therefore, detailed geochemical and petrographic characterization of the Tertiary organic facies of the eastern Chenor area of the Penyu Basin was carried out to characterized its organic matter (OM) source input. Towards achieving the goal, this study focuses on determination of organic matters richness, type and origin as related to their paleoenvironmental conditions of the carbonaceous mudstone and shale using organic petrography combined with organic and inorganic geochemistry. The sedimentary succession is characterized by fine to coarse grained sandstone occurring in association with carbonaceous mudstone and shale in a predominantly fining upward sequence within a lacustrine environment. These facies are generally enriched in organic matter as indicated by the TOC results, hydrocarbon yield (S2) and extractible organic matter (EOM), suggesting significant hydrocarbon generation potential for the area.