| Abstract: | Two hydrocarbon gas seeps, located about 13 km apart, have distinctive molecular and isotopic compositions. These seeps occur within separate tectonic melange units of narrow parallel trending and structurally complex zones with incorporated upper Cretaceous and Palaeogene passive continental margin deposits which are now compressively deformed and imbricated along the convergent Hikurangi margin of North Island, New Zealand. At Brookby Station within the Coastal High, the seeping hydrocarbon gas has a methane/ethane ratio of 48 and ??13C and ??D values of methane of -45.7 and -188???, respectively (relative to the PDB and SMOW standards). Within the complex core of the Elsthorpe Anticline at Campbell Station seep, gas has a methane/ethane ratio of about 12000, and the methane has ??13C and ??D values of -37.4 and -170???, respectively. The source of the gases cannot be positively identified, but the gases probably originate from the thermal decomposition of organic matter in tectonically disturbed upper Cretaceous and/or lower Tertiary sedimentary rocks of passive margin affinity and reach the surface by migration along thrust faults associated with tectonic melange. The geochemical differences between the two gases may result from differences in burial depths of similar source sediment. ?? 1989. |
| Genre: | Article |
| ProdID: | 70015434 |
| Citation Author: | Kvenvolden, K. A.; Pettinga, J. R. |
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| Citation End Page: | 8 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Marine and Petroleum Geology |
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| Citation Number Of Pages: | 7 |
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| Citation Publisher: | Elsevier |
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| Citation Search Results Text: | Hydrocarbon gas seeps of the convergent Hikurangi margin, North Island, New Zealand; 1989; Article; Journal; Marine and Petroleum Geology; Kvenvolden, K. A.; Pettinga, J. R. |
| Citation Start Page: | 2 |
| Citation Volume: | 6 |
| Citation Year: | 1989 |
| Type: | citation/reference |
| Text: | Hydrocarbon gas seeps of the convergent Hikurangi margin, North Island, New Zealand; 1989; Article; Journal; Marine and Petroleum Geology; Kvenvolden, K. A.; Pettinga, J. R. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1016/0264-8172(89)90071-8 |
| Date Other: | Sun, 1 Jan 1989 00:00 -0600 |
| Publisher: | Elsevier |
